United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical

Report RMRS-GTR-144

March 2005

Big Sagebrush: A Sea

Fragmented into Lakes,

Ponds, and Puddles

Bruce L. Welch

Distribution of big sagebrush in the State of

Washington after settlement

Distribution of big sagebrush in the State of

Washington before settlement.
Abstract ______________________________________

Welch, Bruce L. 2005. Big sagebrush: A sea fragmented into lakes, ponds, and puddles.

Gen. Tech Rep. RMRS-GTR-144. Fort Collins, CO: U.S. Department of Agriculture, Forest

Service, Rocky Mountain Research Station. 210 p.

Pioneers traveling along the Oregon Trail from western Nebraska, through Wyoming and

southern Idaho and into eastern Oregon, referred to their travel as an 800 mile journey through

a sea of sagebrush, mainly big sagebrush (Artemisia tridentata). Today approximately 50

percent of the sagebrush sea has given way to agriculture, cities and towns, and other human

developments. What remains is further fragmented by range management practices, creeping expansion of woodlands, alien weed species, and the historic view that big sagebrush is

a worthless plant. Two ideas are promoted in this report: (1) big sagebrush is a nursing mother

to a host of organisms that range from microscopic fungi to large mammals, and (2) many

range management practices applied to big sagebrush ecosystems are not science based.

Keywords: Artemisia tridentata, distribution, canopy cover relationships, fire interval, nutritive

value

The Author ____________________________________

Bruce L. Welch is a plant physiologist with the Rocky Mountain Research Station

in Provo, UT. He earned a B.S. degree from Utah State University in 1965 and an

M.S. in 1969 and Ph.D. in 1974 from the University of Idaho. He has been a Forest

Service scientist since 1977.

The use of trade or firm names in this publication is for reader information and does not

imply endorsement by the U.S. Department of Agriculture of any product or service

CAUTION:

PESTICIDES

Pesticide Precautionary Statement

This publication reports research involving pesticides. It does not

contain recommendations for their use, nor does it imply that the uses

discussed here have been registered. All uses of pesticides must be

registered by appropriate State and/or Federal agencies before they can

be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals,

desirable plants, and fish or other wildlife—if they are not handled or

applied properly. Use all pesticides selectively and carefully. Follow

recommended practices for the disposal of surplus pesticides and

pesticide containers.
Big Sagebrush: A Sea

Fragmented into Lakes,

Ponds, and Puddles

Bruce L. Welch
Preface ________________________

Ode to Sagebrush

What an amazing plant; the sage, so many faces has it.

The most versatile of our shrubs. High value must be placed upon it.

So many creatures large and small get winter food source from it.

The pungent leaves forever fresh when others are dormant beside it.

Break the wind and catch the snow, the ground is safe around it.

What a conservationist this plant! Why don’t more people know it?

Caretaker of the soil, protecting dormant seeds beneath it.

So the desert can once more bloom when conditions are right for it.

And summer too receives a share of favors coming through it.

The shade, the cover, and nests that birds have built within it.

Insect galls on the limbs and burrows dug below it.

What a vast variety of life, find home and solace in it.

Paintbrush, so beautiful and fine, could not survive without it.

Pushing down roots to attached below, nourishment coming of it.

In fall it blooms and beauty gives to all the land about it.

The autumn days delight the air. Smell the aromas that cause it!

How often I have heard the phrase: “It’s just sagebrush,

let’s remove it.”

So naive these people are to fasten that opinion to it.

I once thought of sage as drab before I really knew it.

Now I view it in another light, and attach much beauty to it.

Dave Hanks, Biology Teacher—Burley High School, Idaho; reprinted

from the Idaho Wildlife, March/April 1985, page 16

The above poem by a Burley High School biology

teacher shows an incredible amount of insight into the

ecology and value of big sagebrush (Artemisia tridentata).

This general technical report supports the ecological

principles and value of big sagebrush as expressed in the

poem. Over 1,600 scientific and nonscientific articles

concerning big sagebrush have been reviewed; many

are cited within these pages.

The subject matter covered in this general technical

report can be obtained by scanning the table of contents

and need not be repeated here.

You may order additional copies of this publication by sending your

mailing information in label form through one of the following media.

Please specify the publication title and number.

Telephone (970) 498-1392

FAX (970) 498-1396

E-mail rschneider@fs.fed.us

Web site http://www.fs.fed.us/rm

Mailing Address Publications Distribution

Rocky Mountain Research Station

240 West Prospect Road

Fort Collins, CO 80526

After studying the big sagebrush ecosystem for 30

years, I have come to three conclusions:

1. Much misinformation concerning the value and

ecology of big sagebrush exists in the land management

community.

2. The perceived shortcomings of big sagebrush are a

result of livestock grazing.

3. Big sagebrush is a nursing mother to a host of

organisms ranging from microscopic to large mammals.

I hope that those who read this general technical report

will come to the conclusion that big sagebrush is a valuable

plant species worth preserving. I am, Bruce L. Welch.

Acknowledgments ______________

I wish to thank those who provided peer reviews for

various chapters of this publication. They were: three anonymous reviewers (entire manuscript), Mr. Sherel Goodrich

(entire manuscript), Mr. Stanley G. Kitchen; Drs. John W.

Connelly, Larry S. Jeffery, Rudy King, E. Durant McArthur

(entire manuscript), Susan E. Meyer, David L. Nelson,

Thomas M. Quigley (entire manuscript), Michael F. Whiting,

Joel G. Peterson, Gerald Rehfeldt, Nancy L. Shaw, Carl L.

Wambolt, and Darrell J. Weber. Their contributions were

invaluable and gratefully received. I received great quantities of encouragement from the following: Mr. Craig

Criddle, Mr. Robert L. Elderkin, Dr. Jordon C. Pederson,

Dr. Fred J. Wagstaff, and Mrs. Susan A. Welch. I give to

them my deepest thanks. And to Dr. E. Durant McArthur,

Dr. Janine Powell, and Dr. Jack Wade, who have

earned my deepest respect for their courageous support of this work, my many thanks.

Dedication _____________________

Whatever honor there may be in this publication, I wish

to dedicate it to the following: Drs. Alan A. Beetle, Rexford

F. Daubenmire, Howard R. Leach, and Arthur D. Smith—

all pioneers in big sagebrush research.
Contents

Page

Chapter I: Getting acquainted with big sagebrush. ..............................................1

Distribution .......................................................................................................1

Climate .......................................................................................................1

Woodrat middens .......................................................................................2

Pollen spectrum from lakes, bogs, and peats ............................................4

Historic accounts of big sagebrush ............................................................5

Modern distribution .....................................................................................8

Has big sagebrush invaded grasslands? .................................................12

Relationship between grazing and big sagebrush canopy cover...................12

How much of the big sagebrush ecosystem is left?.......................................15

Life expectancy ..............................................................................................15

Morphology and anatomy ..............................................................................16

Inflorescence versus vegetative branches ...............................................16

Floral development ...................................................................................17

Embryo, seed development, and anatomy ...............................................17

Leaf anatomy and development ...............................................................17

Stem anatomy and development..............................................................18

Root morphology ......................................................................................19

Soils of big sagebrush ...................................................................................20

Big sagebrush taxonomy and origin ..............................................................25

References ....................................................................................................27

Chapter II: Birds, mammals, and reptiles associated with big sagebrush ..........47

Birds ............................................................................................................47

Obligate bird species ................................................................................47

Sage grouse........................................................................................47

Sage thrasher, Brewer’s sparrow, sage sparrow ................................53

Facultative birds species ..........................................................................54

Mammals .......................................................................................................57

Small mammals ........................................................................................57

Pygmy rabbit .......................................................................................57

Sagebrush vole ...................................................................................58

Other small mammals .........................................................................58

Large Mammals........................................................................................64

Pronghorn ...........................................................................................64

Mule deer ............................................................................................66

Elk .......................................................................................................68

Rocky Mountain bighorn sheep ..........................................................70

Desert bighorn ....................................................................................70

Domestic sheep ..................................................................................70

General comments..............................................................................71

Reptiles ....................................................................................................71

References ....................................................................................................73

Chapter III: Other foragers and winter damage on big sagebrush .....................81

Diseases of big sagebrush ............................................................................81

Nonparasitic diseases ..............................................................................81

Parasitic diseases ....................................................................................83

Fungi ...................................................................................................86

Insects and other arthropods of big sagebrush .............................................86

Aphids and other parasites.......................................................................86

Beetles .....................................................................................................89

Defoliator ..................................................................................................90

Crickets, grasshoppers, and katydids ......................................................91

Cicadas ....................................................................................................92
Thrips .......................................................................................................93

Gall inducers ............................................................................................93

Ants ..........................................................................................................94

Spiders .....................................................................................................95

Scorpions .................................................................................................97

Lichens ..........................................................................................................98

Parasitic plants ..............................................................................................99

Paintbrushes ............................................................................................99

Owl-clovers.............................................................................................101

Other parasitic plants .............................................................................101

Sego lilies in a stand of Wyoming big sagebrush ........................................101

References ..................................................................................................102

Chapter IV: Big sagebrush chemistry and water relations ...............................107

Nutritive value ..............................................................................................107

Dry matter...............................................................................................107

Energy-producing compounds ...............................................................108

Protein ....................................................................................................108

Minerals ..................................................................................................108

Vitamins..................................................................................................108

Factors affecting nutritive content of big sagebrush ...............................110

Value of specific nutrients in big sagebrush ...........................................110

Secondary metabolites ................................................................................114

Monoterpenoids......................................................................................115

Chemistry and production .................................................................115

The monterpenoid controversy .........................................................116

Methyl jasmonate ...................................................................................119

Sesquiterpenoids....................................................................................119

Phenolic compounds ..............................................................................120

Allelopathy ...................................................................................................120

Issue of bare ground cover and grass cover ...............................................124

Big sagebrush cover versus bare ground cover .....................................124

Big sagebrush cover versus perennial grass cover................................127

Nitrogen metabolism ....................................................................................130

Phosphorus metabolism ..............................................................................132

Trace elements ............................................................................................133

Photosynthesis and carbohydrate metabolism ............................................133

Photosynthesis .......................................................................................133

Carbohydrate metabolism ......................................................................135

Water relationships ......................................................................................136

Hydraulic lift ............................................................................................137

Big sagebrush water potentials compared to other plant species ..........138

Global warming ......................................................................................140

References ..................................................................................................140

Chapter V: Big sagebrush genetics..................................................................149

Chromosome number ..................................................................................149

Polyploidy ....................................................................................................150

Hybridization ................................................................................................151

Variability .....................................................................................................155

Preference ..............................................................................................155

Digestibility .............................................................................................158

Crude protein..........................................................................................159

Monoterpenoids......................................................................................159

Growth ....................................................................................................161

Germination ............................................................................................163

Summary ................................................................................................164

Selection and breeding ................................................................................164
Selection.................................................................................................164

‘Hobble Creek’ mountain big sagebrush ................................................164

Gordon Creek Wyoming big sagebrush .................................................165

Breeding .................................................................................................165

References ..................................................................................................167

Chapter VI: Putting big sagebrush back into its ecosystem .............................171

Establishment ..............................................................................................171

Direct seedling........................................................................................171

Selection of seed source ........................................................................171

Seedbed preparation ..............................................................................172

Planting ..................................................................................................174

Interseeding............................................................................................175

Transplanting bareroot and containerized stock ....................................175

Mother plant technique ...........................................................................178

Seed production...........................................................................................178

Reproductive growth ..............................................................................178

Seed dispersal........................................................................................179

Seed increase gardens ..........................................................................179

Harvesting and cleaning big sagebrush seed ........................................180

Harvesting .........................................................................................180

Seed cleaning ...................................................................................181

Seed storage ..........................................................................................182

References ..................................................................................................183

Chapter VII: Consequences of controlling big sagebrush ................................187

Negative impacts of big sagebrush control ..................................................188

Does killing, thinning, or controlling big sagebrush

increase grass production? ...............................................................190

Does killing, thinning, or controlling big sagebrush

increase biodiversity? .......................................................................194

Is big sagebrush a highly competitive, dominating,

suppressive species?........................................................................195

Recovery of big sagebrush after fire and fire interval ..................................196

Recovery after fire ..................................................................................196

Fire interval.............................................................................................198

Effects of fire on the big sagebrush ecosystem ...........................................199

Effect of fire on soil chemistry ................................................................199

Water repellancy ....................................................................................199

Othe fire effects ......................................................................................199

Removing big sagebrush .............................................................................200

Prescribed burning .................................................................................200

Season of the year ............................................................................200

Size of fire .........................................................................................200

Rest and deferment ..........................................................................200

Prescription development .................................................................200

Safety ................................................................................................201

Chemical control.....................................................................................201

Mechanical control .................................................................................203

Plowing/disking .................................................................................203

Disk-chain .........................................................................................203

Root plow ..........................................................................................203

Anchor chain .....................................................................................204

Railer.................................................................................................204

Pipe harrow .......................................................................................204

Rotobeater ........................................................................................204

Combining burning and mechanical control techniques .........................204

References ..................................................................................................204

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 1

Chapter

I

This chapter describes the distribution, life expectancy, morphology, soils, and taxonomy of big sagebrush (Artemisia tridentata). Perhaps the most important question

addressed in this chapter is: How much of the big sagebrush ecosystem remains?

Distribution ______________________________________________________

The distribution or range of big sagebrush depends on climate and has fluctuated for

the past 30 millennia. In general, big sagebrush favors areas that receive the majority

of their precipitation in winter months and the least in summer months (Cook and Irwin

1992; Smith 1940; Whitlock and Bartlein 1993).

Climate

Climate is the prevailing weather condition of temperature, barometric pressure,

humidity, precipitation, sunshine, cloudiness, and wind throughout the course of many

years. The driving force is the sun. It is the uneven heating of Earth—greater solar

heating of the tropic regions than the polar regions—that stirs the atmosphere into

motion on an intraplanetary scale and creates Earth’s major wind systems. It is this

wind system, interacting with Earth’s surface topography and bodies of water that bring

cold, warm, moist, or dry air to a given region. The global wind system is in constant

motion as it pumps tropical warm air toward the poles while moving cooler air back

toward the tropics. All the time the wind system is being twisted by Earth’s rotation into

vast rivers of air with an eastwardly direction, interacting with oceans and continents,

climbing mountain ranges and sinking into lowlands, but forever on the move. This

relentless stirring of the atmosphere creates contrasting weather patterns as the wind

system circumnavigates Earth. Repeated over a course of many years, climate is formed

from these contrasting weather patterns. Still, these patterns can be interrupted by

variations in the output of the Sun; eruptions of volcanoes that spread ash in the upper

atmosphere and in effect reduce the heating of the planet; the uplifting of mountains and

plateaus, which intercept moisture and create rain shadows, discordances between air,

oceans, and polar ice or the lack there of; and the gravitational tug of other celestial

bodies that slightly reshapes Earth’s orbit (eccentricity), the tilt of its axis (obliquity),

and the time of year when the Earth-Sun distance is maximum or minimum (precession). All of these may redistribute the heating of Earth and cause great changes in the

climate of a given region (Schoonmaker and Foster 1991).

Getting Acquainted With

Big Sagebrush
2 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

For most of the past 100 millennia, the climatic

conditions throughout the range of big sagebrush were

dominated by the Wisconsin glacial epoch of the Quaternary period, which ended about 8,000 years ago

(Antevs 1948).

In fact, the whole Quaternary period comprising the

past 1.6 to 2.0 million years has been a period characterized by alternating wet and cool and dry and warm

climates (Schoonmaker and Foster 1991). During this

period some 24 glacial events have been identified,

making the Quaternary period a colder period as

compared to the warmer Tertiary period (Schoonmaker

and Foster 1991). Glacial stages during the Quaternary period have lasted from 50,000 to 100,000 years.

These glacial events result in slow formation of large

ice sheets in the high latitudes in an “oscillatory”

fashion and end with a rapid melting of the ice sheets,

followed by a warming interglacial interlude of some

10,000 to 20,000 years (Schoonmaker and Foster 1991).

It is believed that this alternation between glacial and

interglacial interludes is caused by the cyclical alteration of Earth’s orbit around the Sun (Schoonmaker

and Foster 1991). This alteration of Earth’s orbit

comprises three components: eccentricity, obliquity,

and precession. All three are themselves cyclic. Eccentricity, which is the degree that Earth’s orbit varies

from a perfect circle about the Sun, varies from 0 to 6

percent on a 100,000-year cycle and affects the distance between Earth and Sun (Schoonmaker and

Foster 1991). Obliquity refers to the tilt of Earth on its

axis; this varies from 22 to 24.5 degrees on a 41,000-

year cycle and affects the latitudinal heating of the

planet (Schoonmaker and Foster 1991). Precession, or

time of year when maximum or minimum distance

between Earth and Sun occurs, varies about 10 percent on a 22,000-year cycle and affects seasonality

(Schoonmaker and Foster 1991). It is the interplay of

these three cycles that determines the specific climatic

conditions of a given region and the general climatic

conditions of the entire planet. Based on orbital geometry, a cooling trend is predicted in the next few

thousands years (Schoonmaker and Foster 1991).

Modern weather patterns are described by Antevs

(1948). In the Western Hemisphere, the modern winter weather patterns are characterized by formation of

ice and snow throughout all of the northern land

(Canada). This in turn reflects a large amount of solar

radiation back into space and creates a large cold air

mass. It is this contrast of temperature and pressure

over the frozen north and open oceans and snow-free

and ice-free land that results in the development of

anticyclonic pressure (high pressure) that sends waves

of cold polar air moving southward. This cold air

collides with warm moisture riding on the westerlies

that are generated from the subtropical high pressure

zones located at about 30° latitude. When these air

masses are large enough, semipermanent lows, the

Aleutian Low and the Iceland Low, develop resulting

in contemporary winter weather patterns. With the

tilting of Earth’s axis, which warms the northern land

and thus melts ice and snow, less solar energy is

reflected back into space. In turn, a semipermanent

low pressure zone is established over the continent,

the Aleutian Low is reduced, and a high pressure zone

is formed over the Pacific Ocean at about 40° latitude.

This high pressure causes the near rainless summers

that occur in the big sagebrush ecosystem or deserts of

the Western United States.

The huge unyielding ice sheets created during the

Wisconsin Glacial Epoch resulted in the permanency

of the Aleutian Low pressure field throughout the

summer in spite of rising summer temperatures. This

forced the summer subtropical high pressure field of

the Pacific to form further south, perhaps below 30°

latitude, thus creating a pluvial period for the Western

United States as storm tracts move across the region

throughout the entire year. This contrasts to weather

patterns of the present interglacial interlude of cold,

moist winters and dry, hot summers.

Big sagebrush, like other plant species, has over the

past 20 or 30 millennia adjusted its distribution as

climatic conditions changed, expanding during favorable periods and contracting during unfavorable times

(Antevs 1948; Schoonmaker and Foster 1991). This

expansion and contraction of plant species distribution can be monitored over time by studying fossil

plant parts such as pollen, seeds, leaves, and twigs

contained in lake muds, bogs, peats, and in drier

climates, woodrat (Neotoma sp.) middens

(Schoonmaker and Foster 1991).

Woodrat Middens

Woodrat middens are somewhat analogous to sanitary landfills of humans minus the sanitary part.

Middens are piles of accumulated organic (plant and

animal) and inorganic materials gathered by woodrats

and deposited near and within their dens (Dial and

Czaplewski 1990; Finley 1990). Dial and Czaplewski’s

(1990, p. 47) description:

The midden portion of a modern woodrat den was

considered to be those materials accumulated by the

woodrat, including unused plant clipping, woodrat feces, and faunal materials (bones and insects). Often the

materials were in the process of being coated with or

cemented together by rat urine (i.e., they comprised the

animal’s habitual “toilet” area), but only small portions

were consolidated and indurated with urine.

Other materials such as leaves, pollen, and sand may

be deposited in the middens by means other than

woodrat activities (wind; Finley 1990).

Van Devender and King (1971) studied the plant

macrofossils preserved in woodrat middens in the

Artillery Mountains of southern Mohave County, AZ.

They reported finding what they considered to be
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 3

18,000-year-old big sagebrush leaves occurring in what

is today a Sonoran Desert community. Pollen analysis

of these middens showed the presence of Artemisia

pollen from 10,000 to more than 30,000 years ago or

B.P. (Before Present). Because Artemisia pollen is not

distinguishable at the species level, the authors believe that the pollen found in the various middens was

big sagebrush pollen (Cawker 1983). A modern analogue (big sagebrush) presently grows north and west

of the Artillery Mountains in association with pinyon

and juniper (Jameson and others 1962; Van Devender

and King 1971). Van Devender and King (1971) concluded that from 10,000 to more than 30,000 years

B.P., the Artillery Mountains supported a pinyon/

juniper woodland with abundant big sagebrush, but as

the climate became warmer and drier, sometime after

10,000 years B.P., this plant community could not

survive and yielded to the Sonoran Desert vegetation

of today. Cole (1985) presents evidence that big sagebrush has been present in the Grand Canyon region of

northern Arizona for the past 24,000 years.

Unlike the Van Devender and King (1971) report,

Nowak and others (1994a) found evidence of the presence of big sagebrush in the Painted Hills in the

Virginia Mountains of northwestern Nevada, from

30,000 year B.P. to the present. Their study site was

located about 4.75 miles west of Pyramid Lake, a

remnant of the pluvial Lake Lahontan. Present vegetative cover consisted mainly of Utah juniper

(Juniperus osteosperma), big sagebrush, shadscale

(Atriplex confertifolia), and various bunchgrasses.

They, too, sampled woodrat middens and identified

plant macrofossils found in the various midden

samples. Some of the fossils they were able to identify

as big sagebrush, but a number of others were listed as

being Artemisia sp. However, Nowak and others (1994a,

p. 583) believed that many of the fossils listed as

Artemisia sp. were likely big sagebrush because “A.

tridentata is the dominant species for our locale and

was the only species identified in the fossil record.” An

interesting point of the Nowak and others (1994a)

study is the occurrence of big sagebrush throughout

the fossil record, in spite of large changes in local and

regional climatic conditions.

Two possible explanations may account for big sagebrush longevity at this site: first, the site may have

been a refugium for big sagebrush (that is, an area of

relatively unaltered climate not totally reflecting the

continental climatic changes that occur during glacial

and interglacial periods). Or, second, big sagebrush

may have possessed a high degree of genetic variability. Nowak and others (1994a, p. 588) favor the latter:

Plants of the sagebrush steppe of the northern Great

Basin appear to possess a high degree of genetic variability within a species, which allows these species to

tolerate a high degree of climatic variation. Evidence

for a high degree of genetic diversity within a variety of

modern Great Basin shrub species comes from modern

plant ecology studies conducted by the [USDA Forest

Service] Shrub Laboratory and by other scientists.

The genetic richness of big sagebrush is discussed in

chapter V. They further found a trend from a higher

proportion of herbaceous species to a higher proportion of shrubby species as the climate became warmer

and drier from the Pleistocene epoch to the current

Holocene epoch.

Nowak and others (1994b) found big sagebrush

macrofossils occurring in woodrat middens sampled at

11 sites in western Nevada and east-central California

near the Nevada-California border. All macrofossils

were at least 1,000 years old and many older. Big

sagebrush is present in the modern vegetation at all

sites except one (Hot Springs Mountains).

About 250 miles east of the Lahontan Basin and

within the vicinity of the Bonneville Basin, the story of

big sagebrush macrofossils in woodrat middens is

similar. Rhode and Madsen (1995), studying plant

macrofossils from 15 woodrat middens scattered

throughout the vicinity of the Bonneville Basin, found

evidence of big sagebrush at all 10 locations. Age of

these middens varied from 9,000 to 14,000 years B.P.

and varied in elevation from 4,840 to 6,600 feet.

Abundance of big sagebrush among the middens varied from rare to dominant. The authors concluded that

cold montane steppe, dominated most likely by big

sagebrush, covered most of the western Bonneville

Basin some 13,000 years ago. After this time and until

for a relatively brief period 10,800 years ago, Rhode

and Madsen (1995) suggest that limber pine (Pinus

flexilis) woodlands expanded into the region and then

retreated upslope because of drier climatic conditions

that followed. Big sagebrush, however, persisted in

spite of climatic changes (wetter) and the expanding

limber pine woodland, and remained there during the

drying period and decline of the limber pine woodland,

even to the present day

Thompson (1990), using midden evidence, argued

that 34,000 years B.P. big sagebrush in the eastern

Great Basin (northern Snake Range of Nevada) commonly grew with bristlecone pine (Pinus longaeva)

and currant (Ribes sp., not identified); at 18,000 years

B.P. big sagebrush grew with bristlecone pine, currant, prostrate juniper (Juniperus communis), Engelmann spruce (Picea engelmannii), and Rocky Mountain juniper (Juniperus scopulorum); at 7,000 years

B.P. it grew with bristlecone pine, prostrate juniper,

limber pine, Rocky Mountain juniper, and Rocky Mountain maple (Acer glabrum); and by 2,000 years B.P. all

these species, except big sagebrush, were absent in

woodrat midden fossil records. He concluded, based on

the studies he reviewed, that during the late Pleistocene

epoch, sagebrush (most likely big) maintained its modern geographic ranges. It is suggested in Thompson

(1990) that much of the historical woodlands, montane,
4 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

and subalpine vegetation of the Great Basin was an

overlay of a continuous matrix (mostly) of big sagebrush habitat. Tausch (1999, p. 15) makes a similar

statement for today:

With the full perspective of Holocene history, plant

species found in the understory of today’s woodlands,

and in the majority of locations, have generally existed

in a variety of shrub and grass-dominated communities

for far longer periods of time than they have in treedominated communities. Because tree-dominated woodlands have been much more temporary or transitory, it

is the nontree-dominated communities that are the

matrix within which are imbedded pockets of woodlands of various successional stages.

Mehringer and Wigand (1990) studied the macrofossils (leaves, stems, seeds, buds) and microfossils (pollen) of woodrat middens located in the Diamond Craters area of southeastern Oregon. Ages of their middens

range from 800 to 4,000 years B.P. All 24 woodrat

middens examined showed a dominance of juniper and

Artemisia in both the macrofossil and microfossil spectrum. There is a high probability that the dominant

Artemisia was big sagebrush. Big sagebrush is the

dominant shrub of present day vegetation. Mehringer

and Wigand (1990, p. 309) described their findings:

“Pollen from the interiors of twelve middens from

Diamond Craters corresponds to the macrofossils in

their monotonous predominance of juniper and sagebrush pollen.”

Koehler and Anderson (1995) were able to construct

a 31,000-year-old vegetative history-pollen spectrum

for the Alabama Hills of Owens Valley, CA, from

woodrat middens. The presence of big sagebrush was

continuous throughout the 31,000-year period in spite

of the disappearance of juniper 5,000 years ago; the

decline started about 17,000 years ago with the waxing and waning of other species. The big sagebrush

pollen profile is the least variable of 13 pollen profiles

studied.

So, what have we learned from the study of woodrat

middens? That big sagebrush persisted throughout

the Great Basin, central Oregon, and east-central

California for thousands of continuous years and on

some sites for more than 30,000 years. Big sagebrush

in humanistic terms is a long-term survivor.

Pollen Spectrum From Lakes, Bogs, and

Peats

Pollen records from lake muds, bogs, and peats

furnish still more evidence that big sagebrush is a

long-term survivor not only in the Great Basin and

central Oregon but at other Western United States

locations. Artemisia pollen cannot be identified as to

species. This section cites studies whose Artemisia

pollen spectrum would have a high probability that

some, if not most, of the pollen was derived from big

sagebrush.

Five fossil pollen studies have been conducted in and

around Yellowstone National Park (Baker and Richmond 1978; Waddington and Wright 1974; Whitlock

1993; Whitlock and Bartlein 1993; Whitlock and others 1995). While the five studies’ emphases were

concentrated on the reaction of tree species to changes

in climate, all reported significant amounts of Artemisia fossil pollen throughout their various constructed

pollen spectrums from 14,000 to 70,000 years B.P. to

the present. Based on modern analogues, of the presence of big sagebrush throughout the region, some if

not most of the Artemisia pollen found were probably

produced by big sagebrush plants (Beetle and Johnson

1982). The percentage of Artemisia pollen in the pollen

spectra peaked about 14,000 years B.P. and has persisted continuously at a lower level to the present, in

spite of changes in climatic conditions and changes

through time in tree species composition at the various

study sites. In other words, tree species came and went

as climatic changes occurred, but big sagebrush still

persisted. Moving the scene to the southeast to the

Wind River Mountain Range of Wyoming and increasing the elevation to 10,100 feet, we see the same

story—a 12,000-year pollen spectrum history showing

the persistence of big sagebrush (Fall and others

1995).

Madsen and Currey (1979) describe four glaciation

periods during the past 26,000 years in Little Cottonwood and Bell Canyons in Utah’s Wasatch Mountains.

The earliest of the four (Dry Creek till) reached the

mouth of Little Cottonwood Canyon some 26,000 years

ago and then receded for a time until about 19,000

years ago. A second glacier (Bells Canyon till) formed

and pushed its way down to the mouth of the canyon;

it too receded. Then about 12,300 years B.P., several

glaciers (Hogum Fork till) were formed and pushed

their way to mid-canyon and then receded. Again

about 7,500 years ago, a fourth glacier (Devils Castle

till) was formed and pushed its way a small distance

from where it was formed (Devils Castle area), and it

also receded. During these 26,000 years the climatic

conditions varied among four possibilities: cool/wet,

cool/dry, warm/dry, and warm/wet. Still the pollen

spectrum of this area demonstrated the persistence of

big sagebrush throughout the period of climatic

changes. Madsen and Currey (1979, p. 264), concerning the finding of their fossil pollen study, stated:

Together these pollen types suggest a dominance of

alpine meadows on moist canyon bottoms, a sagebrushdominated community on ridge sides and knolls, and a

large community of alder, birch, and willow along

stream sides. Plant communities of this type are presently found at elevations of 2,650 to 2,900 m in the

canyon and apparently existed at lower elevations

several times during the Holocene.

In the Chuska Mountains of northwestern New

Mexico, big sagebrush has persisted in the fossil
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 5

pollen record for about 50,000 years (Wright and

others 1973).

After observing evidence for the presence of big

sagebrush pollen throughout three pollen diagrams

from southern British Columbia, Cawker (1983, p.

1126) concluded:

The increasing dominance of grasslands after 1890 by

Artemisia tridentata and other woody shrubs has often

been attributed to overgrazing by domestic livestock,

but pollen data indicate that shrub populations were

substantial in presettlement times, and that the recent

“invasion” represents a recovery from anomalously low

population levels during the middle 19th century.

Wigand (1987, p. 427) presents similar data from

central Oregon for the past 6,000 years

and concluded: “Since the mid-1800s man and changing climate have encouraged sagebrush reexpansion.”

Big sagebrush pollen was found to be continuously

present in a fossil pollen spectrum from the Dome

Creek (3,165 m) area of northwestern Colorado (Feiler

and others 1997). The period covered from 10,600

years ago to 120 years ago, during which the pollen

profiles of several species were not continuous (Feiler

and others 1997). Even though the study site is in a

subalpine zone, Feiler and others (1997, p. 54) noted

that Artemisia steppe, dominated by big sagebrush,

“occurs at least as high as 3,050 m on portions of the

drier, south-facing side of the drainage.”

In southeastern Oregon, a big sagebrush pollen

profile was continuous from 2,000 years ago to the

present (Mehringer and Wigand 1990). This is in

agreement with the woodrat middens analysis covering a period of 800 to 4,000 years B.P. cited earlier in

this section. Other areas where big sagebrush pollen

profiles are reported as being continuous for thousands of years are: Great Salt Lake, Utah; Swan and

Grays Lakes, Idaho; and Sheep Mountain Bog, Montana (Beiswenger 1991; Bright 1966; Mehringer 1985).

What have we learned from all these macrofossil

and microfossil studies? Beetle and Johnson (1982)

noted that big “sagebrush is where sagebrush was”;

only now, “was” can be defined in terms of tens of

thousands of years (Bright 1966; Johnson 1986). The

converse of this statement is not necessarily true;

there are areas where big sagebrush was during earlier climatic regimes but has given way to other vegetative types, such as Sonoran Desert vegetation of the

Artillery Mountains of Arizona (Van Devender and

King 1971) and coniferous forests of northeastern

Washington and northern Idaho (Mehringer 1985).

Historic Accounts of Big Sagebrush

Lewis and Clark described what was probably big

sagebrush on April 14, 1805, near the mouth of the

Little Knife River, ND (Coues 1965). Another possibility would be plains silver sagebrush (A. cana). On

August 5, 1805, Captain Lewis encountered areas

having little grass but covered with “southernwood” or

big sagebrush as they traveled through the Jefferson

River region of Montana (Coues 1965). They often

sighted sage grouse (Centrocercus urophasianus) as

they traveled through the upper parts of the Missouri

River basin and the plains of the Columbia River

(Coues 1965). The presence of sage grouse is a good

indicator of vast, dense stands of big sagebrush (see

chapter II).

Douglas (1914), as he described it, conducted

“botanising” trips into an area ranging from Fort

Vancouver on the Columbia River to the Blue Mountain of southeastern Washington, to Kettle Falls on

the Columbia River of northeastern Washington, during the years of 1824 to 1827. He collected numerous

samples of Artemisia; most were probably big sagebrush, along the Columbia River of central Washington.

Douglas (1914, p. 180) noted numerous sightings of

sage grouse and stated that they “are seen

abundantly...seen in large flocks...by no means a rare

bird. Raised two large flocks near the Grand Coulee

and had to content myself with a sight of them, having

no gun.” He also noted sage grouse in central Washington

and defined their range from the Cascade Range in the

west to the Great Dividing Range in the east. All sightings

of sage grouse hint at the presence of vast, dense stands

of big sagebrush covering central Washington.

Traveling through Nebraska, Townsend (1834) encountered an Artemisia on May 25, 1833, that was

either big sagebrush or plains silver sagebrush (A.

cana). His description more closely resembles big

sagebrush; the soil it was growing in (poor and sandy)

would tend to support big sagebrush. Nonetheless, the

sagebrush was thick with little grass. West of Laramie’s

fork on the North Platte (Fort Laramie in 1846),

Townsend (1834, p. 183) on June 7, 1833, describes the

country:

The country has now become more level, but the prairie

is barren and inhospitable looking to the last degree. The

twisted, aromatic wormwood covers and extracts the

strength from the burnt and arid soil. The grass is dry

and brown, and our horses are suffering extremely for

want of food. Occasionally, however, a spot of lovely

green appears, and here we allow our poor jaded friends

to halt, and roam without their riders, and their satisfaction and pleasure is expressed by many a joyous neigh,

and many a heart-felt roll upon the verdant sward.

The aromatic wormwood spoken of is big sagebrush.

On the Sandy River plains, Townsend (1834, p.188)

noted large herds of buffalo grazing on the short and

dry grass and observed: “Domestic cattle would certainly starve here, and yet the bison exists, and even

becomes fat; a striking instance of the wonderful

adaptation of Providence.” In spite of the presence of

buffalo, Townsend still noted that their poor horses

had to fast as before because there was nothing to eat.

He further noted on June 17, 1833, that some of their

horses ate the tops of big sagebrush “with which the
6 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

plain is strewed.” From the Green River, through

Ham’s Fork and on to the Bear River on July 6 to 8,

1833, Townsend made many sightings of sage grouse,

“but on the plain, nothing flourishes but the everlasting wormwood, or sage as it is here called.” After

spending some time, perhaps a day or two, at WhiteClay Pits on the Bear River (Soda Springs, ID), his

party left on July 10 and in doing so observed (Townsend

1834, p. 202):

Soon after we left, we crossed one of the high and stony

hills by which our late camp is surrounded; then making a gentle descent, we came to a beautiful and very

fertile plain. This, however, very different from the

general face of the country; in a short time, after

passing over the rich prairie, the same dry aridity and

depauperation prevailed, which is almost universal

west of the mountains.

From here the Townsend party moved on to Fort Hall,

ID, and noted, upon crossing the Snake River on

August 6, a wide sandy plain thickly covered with

wormwood or big sagebrush and that their hunters

had killed a few sage grouse. From Fort Hall, the

Townsend party moved in a northwest direction to the

Lost River country of Idaho and then on to Fort Boise.

Most travelers from Fort Hall would travel along the

Snake River to Fort Boise, but the Townsend party

went along the least traveled route. Traveling for

about 4 days in the Lost River country of Idaho,

Townsend said it was, “covered by the eternal sage

bushes.” From the Lost River country of Idaho to the

Blue Mountains of Oregon, big sagebrush and sage

grouse would be their almost constant companions.

Wislizenus (1839), although not the naturalist that

Townsend was, also traveled the same course to Fort

Hall and noted the abundance of big sagebrush from

Nebraska to the Blue Mountains of Oregon. In 1849

Major Osborne Cross and George Gibbs traveled the

same route and noted much big sagebrush (Settle

1940, p. 107–108), adding:

June 29. Our road today passed over a dreary and

uninteresting route—more so than any since leaving

Fort Laramie. The hills are not so high as you approach

the Platte but [are] entirely barren. Nothing was to be

seen but the artemisia or wild sage, which is extremely

uninteresting, having neither beauty nor usefulness to

recommend it and its odor [is] by no means pleasant.

We were destined to travel a very long distance where

this shrub was constantly to be seen in greater quantity

than had been already met with. It may be truly said

that we had just entered it, as it was not very [plentiful]

or large, compared with what we afterwards met with

on the route. There must be something in the composition of the earth particularly adapted to its growth, for

whenever the grass was scarce we invariably found it in

great quantities. I have traveled for days before reaching the Columbia River where nothing could be seen on

the highlands and plains but the artemisia, which for

miles looked as if the whole country had been cleared of

all other vegetation to make room for it.

In 1843 and 1844, Fremont (1845), a trained naturalist, reported to the Congress of the United States much

the same observations of big sagebrush abundance

from Nebraska to Fort Hall, ID, as did the Townsend

report of 10 years earlier (Townsend 1834). But in

addition to the Townsend report, Fremont traveled

down the Bear River through Cache Valley to the

Great Salt Lake and to Fort Hall, and from Fort Hall,

along the Snake River, whereas Townsend moved

northwest from Fort Hall to the Lost Rivers country

and then west to Fort Boise. Both naturalists traveled

to the Blue Mountains of Oregon. Fremont’s journey

took him down the Columbia River to the Dalles and

from there to Pyramid Lake through central California, southern Nevada and Utah, and north-central

Utah. During this long trek, Fremont recorded the

domination of big sagebrush in Nebraska, Wyoming,

Idaho, Oregon, Washington, Nevada, California, and

Utah. While traveling to Fort Hall, ID, on September

16, 1843, Fremont (1845, p. 161) made an astute

observation concerning big sagebrush: “This plant

loves a dry, sandy soil, and cannot grow in the good

bottoms where it is rich and moist, but on every little

eminence, where water does not rest long, it maintains

absolute possession.”

Gruell (1986, p. 3) also quoted this statement of

Fremont and concluded: “By inference, Fremont’s statement suggests that grasses commonly occupied deep

soils. Because sagebrush was capable of growing on

these sites, there is reason to believe that it was

excluded by fire.” The key words of the Fremont’s

statement are “bottoms,” “moist,” and “water does not

rest long.” The bottoms spoken of are valley bottoms

with a river or creek flowing through it and the zone

impacted by the river’s water commonly known as

riparian zones or the rising of water table by the flow

of ground water from mountain slopes into valley

bottoms. These zones can be narrow like a small creek

running through a big sagebrush stand or large like

the Bear River flowing through Cache Valley, UT.

“Moist” and “water does not rest long” refer to the fact

that big sagebrush cannot survive long in watersaturated soils.

There is a physiological and pathological explanation for Fremont’s astute observation. The oxygen

requirement for big sagebrush root development,

growth, and survival is high. During periods of high

soil-water content, plants become stressed, enabling

soil-borne plant pathogens to enter the root system,

killing the roots of established plants, in the case of

flooding, or killing the roots of seedlings, whose seeds

fell into a riparian zone or area of high water table

(Caldwell 1979; Lunt and others 1973; Nelson and

Krebill 1981; USSCS 1950). In fact, Ganskopp (1986)

suggests flooding or water spreading as a technique to

control Wyoming big sagebrush. Sturges (1989, p. 1035)

noted: “[Mountain big] sagebrush on the downwind

side of the [snow] fence was eliminated by the third

growing season, apparently because of the longer

time the soil was saturated.”
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 7

So the exclusion of big sagebrush spoken by Gruell

(1986) probably was not by fire (see Daubenmire 1970

section on aborigines, grazing, and fire; also Welch

and Criddle 2003) but rather by the physiological and

pathological characteristics or limitations of big

sagebrush itself. In many Great Basin valleys, such as

Cache and Malad Valleys, high water tables and

springtime flooding favor the creation of grassy

areas, and grass dominates over big sagebrush

(Thatcher 1959). Fire was noted twice by Townsend

and Fremont in the portions of their reports that I read

(Fremont 1845; Townsend 1834). Two fires were noted

in the coniferous forests of the Blue Mountains of

Oregon and the remaining two in grasslands.

In addition to high a water table, Woodward and

others (1984) suggest that root cation-exchange capacities may also play a role in the differential distribution of big sagebrush and grasses (33.53 versus

14.77 me/100 g).

Stansbury (1852), under orders to survey the Great

Salt Lake of Utah and its valley, corroborates the

earlier reports of Townsend and Fremont concerning

the abundance and dominance of big sagebrush from

Fort Laramie to Fort Hall and from Fort Hall to the

Great Salt Lake. While surveying the Great Salt Lake,

Stansbury (1852) referred to the presence of big sagebrush many times:

April 12, 1850, “cooking was furnished by the wild sage”;

April 30, “the camp pitched in a thicket of grease-wood

and artemisia”;

May 1, “in wandering among the artemisia”;

May 10, “here we found that we had still half a mile

farther to go to reach the nearest artemisia-bushes,

which have now become our sole dependency for fire

wood gave shelter to shoals of gnats”;

May 13, “we found, to our dismay, that an extensive flat

of sand still lay between us and the line of grass and

bushes where alone we could obtain fuel for cooking.

Over this, the camp was carried upon weary shoulders,

and pitched among some artemisia”;

At this same location Stansbury noted: “The place had

long been a resort for the few Indians that occasionally

pass through this inhospitable region. Remains of old

lodges constructed of sage-bush, beds of the same...”;

May 16, another entry about using big sagebrush for

cooking;

May 28, the vegetation was the ever-recurring artemisia, bunch-grass, and a few scattering dwarf cedars no

more than 10 feet high; and the accounts of encounters

with big sagebrush continued.

Watson (1871, p. 27) observed this about big sagebrush in the Great Basin:

Sometimes mingled with them, but wholly free from

alkaline preferences and beyond their range usurping

entire predominance is the everlasting sagebrush, the

Artemisia tridentata. This is by far the most prevalent

of all species, covering valleys and foothills in broad

stretches farther than the eye can reach, the growth

never so dense as to seriously obstruct the way but very

uniform over large surfaces, very rarely reaching the

saddle-height of a mule and ordinarily but half that

altitude.

Wakefield (1936, p. 14) who studied the private

diaries of explorers and pioneers, historical government reports of geological explorations, and other

records, concerning the plant communities of Salt

Lake and Utah Valleys, concluded: “The evidence

seems to show that there was originally a much larger

proportion of grasses on the bench lands than sagebrush or oak.” Of interest about his article is the

vegetative description of Utah Valley. Along the eastern side much grass and little big sagebrush grow; but

on the west side, “They say the wild sage is very

plentiful.” By the year 2000, little big sagebrush was

present on the foothills along the eastern side of Utah

Valley, as viewed from the United States Forest Service, Shrub Sciences Laboratory. Big sagebrush can be

found in varying degrees on some sites on the east side

such as above Pleasant Grove, UT, but for the most

part big sagebrush is not dominant until southwest of

Spanish Fork, UT. However, Tanner (1940, p. 48)

quoted historic evidence of a mixture of “bunch grass

and sage-brush that covered much of the land around

American Fork,” and Emma Evans Stratton stated in

her diary published in the Orem-Geneva Times July

16, 1997: “There [were] about 15 families on the bench

between Lindon and the river bridge. There were no

fences and no roads, just sagebrush as far as the eyes

could see. If we wanted to go to the canyon or visit a

neighbor, we just cut through the sagebrush and made

our roads...” On the west side of Utah Valley, the story

is quite different. Big sagebrush dominates the foothills along the entire length of the valley and is lacking

only on ground being farmed or where fire has destroyed it. As Stewart (1941, p. 364) pointed out:

“Thus, the soils in the heart of the sagebrush zone have

been found the most suitable of all Great Basin soils

for cultivated agriculture.” Thus, based on the historic

evidence presented by Wakefield (1936), big sagebrush is currently found where big sagebrush was in

the past in Utah Valley (Johnson 1986).

Johnson (1986) conducted a fascinating photographic

study of “sagebrush over time.” He selected 20 landscape photographs taken by William H. Jackson in

Wyoming, Utah, and Idaho during the 1870s while

Jackson was a member of Hayden’s survey company,

and Johnson returned to these landscapes and took

current (1974 though1985) photographs from the same

photopoints. Comparing Jackson’s photographs with

the modern photographs over 100 years later, Johnson

(1986, p. 223) concluded that “there has been no major

shift in sagebrush distribution as a result of use,” and

“the appearance of the landscape today is a fair indication of its appearance in presettlement times.”
8 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Young and others (1979) noted that the use of historical records can be used to justify any preconceived

ideas of presettlement vegetation and added (p. 2):

“Good sources for quotations from most of the journals

written during the contact period are Stewart (1941),

who emphasized the abundance of grass under pristine conditions, and Vale (1975) who concluded the

opposite and stressed shrub dominance.” I have read

and studied both the Stewart (1941) and the Vale

(1975) reports and conclude that they are not contradictory, but that the problem may stem from either a

superficial analysis of the Stewart (1941) report or

bias against big sagebrush.

Here is my analysis of the Stewart (1941) report.

First, Stewart limited his report to the State of Utah,

whereas Vale (1975) was referring to the northern

Intermountain West. Second, Stewart reviewed historical records that were concerned with finding suitable sites for the establishment of permanent settlements in the mid-1800s for members of the Church of

Jesus Christ of Latter-day Saints (LDS), commonly

referred to as “Mormons.” Brigham Young, then president of the LDS church, sent parties out to search for

sites where settlements could be established, so resulting records highlighted soils, water, and availability of timber and native grasses on promising sites.

Stewart (1941, p. 366) described one such search

party: “In 1849 an exploring party crossed what is now

Cedar Valley and over the Oquirrh Mountains in

search of a tract of land on which to pasture livestock.”

The exploring party crossed over a whole valley and

did not find a tract of land on which to pasture

livestock because Cedar Valley was not a valley of

abundant grass. Yet, a few years later the United

States Army would establish a camp in this same

valley, concluding that there was enough grass for

transitory army purposes. The Stewart (1941, p. 366)

report continues: searching on, the exploring party

“found a grass-covered spot” (note the use of the word

spot, not grass-covered valley) “with timber, water,

and moderately good soil” in what is today Tooele

Valley. If the historical records Stewart was reading

are describing abundance of grass under pristine conditions, why the searching? As I read the Stewart

(1941) report, it became quite obvious that the exploring parties had to travel great distances between areas

of abundant grass that could support settlements.

Stewart’s (1941, p. 364) description of settlement sites

used the shrub word “sagebrush” many times and

stated, “Nearly all of them lie almost in the heart of the

sagebrush zone” (not grass zone). Also, as cited earlier,

most of the farmlands near these settlements were

taken out of big sagebrush. Stewart (1941, p. 364)

further observed: “Where the soils and the moisture

supply was somewhat more favorable than ordinary,

as along stream courses, the wheatgrasses and giant

ryegrasses predominated.” Vale (1975, p. 32) made a

similar statement: “Stands of grass apparently were

usually confined to wet valley bottoms, moist canyons,

and mountain slopes, with more extensive areas in

eastern Oregon near the Cascade Range. The major

area was apparently covered by thick stands of brush.”

That the historical records cited in the Stewart (1941)

report gave greater emphasis to the occurrence of

grass is evidence that finding tracts of land producing

an abundance of grass was a rare find, which is in

accord with the conclusions of the Vale (1975) report.

In summary, what do the macro-micro fossil record

and historical records tell us about the distribution of

big sagebrush? First, that big sagebrush has been

present in the Intermountain region and parts of the

Great Plains for tens of thousands of years, and that it

was established in northeastern Washington and northern Idaho before the present day coniferous forests

were established; it was present in northwestern Arizona before giving way to the present day Sonoran

Desert; it was present before the establishment of

some of the pinyon/juniper woodlands; and some woodlands are continuing to expand into present day big

sagebrush habitat. Some of the fossil records parallel

the historical records. Lewis and Clark found it in

North Dakota and across Montana and Washington in

1805. Douglas (1914) strengthens the testimony of

Lewis and Clark concerning the presence of big sagebrush in the State of Washington in 1824. A number of

individuals (Townsend, Wislizenus, Cross and Gibbs,

Fremont, and Stansbury) established the presence of

big sagebrush in what now are the States of Nebraska,

Wyoming, Idaho, Utah, Oregon, Nevada, Washington,

and California during the early and mid-1800s. All

confirming that, in the words of Beetle and Johnson

(1982), big sagebrush is where big sagebrush was.

Modern Distribution

Modern distribution of big sagebrush is illustrated

in figure 1.1 (McArthur 1983; McArthur and Plummer

1978). This distribution map of McArthur and Plummer

(1978) supports both the fossil and the historical

records concerning the occurrence of big sagebrush.

Big sagebrush grows in the following States: North

and South Dakota, Nebraska, Montana, Wyoming,

Colorado, New Mexico, Idaho, Utah, Arizona, Washington, Oregon, Nevada, and California. Also, big

sagebrush stands can be found in northern Baja of

Mexico and southern British Columbia.

The distribution of big sagebrush in the northern

Great Plains is illustrated in figure 1.2 and is summarized by Johnson (1979, p. 47): “In all areas, except

Wyoming and parts of Montana, big sagebrush exhibits the attributes of a plant at the outer reaches of its

range—disjunct populations and concentration on sites
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 9

with favorable soil and moisture conditions.” Hazlett

and Hoffman (1975), studying the pattern of plant

distribution on sites dominated by big sagebrush in

the south unit of the Theodore Roosevelt National

Memorial Park in western North Dakota, describe big

sagebrush as occurring sparsely over the entire area

but dominate (29 percent canopy cover) stands on flat

benches or terraces above the Little Missouri River

and its tributaries.

The distribution of big sagebrush for the Montana is

illustrated in figure 1.3. Morris and others (1976)

found big sagebrush to be widely distributed throughout the State and occurring over a wide range of

elevations and soils. The most common subspecies of

big sagebrush is Wyoming big sagebrush, particular in

eastern Montana where the stands are discontinuous,

but the transition zones between grasslands and big

sagebrush stands can be large; thus Wyoming big

sagebrush and the other subspecies can occupy areas

greater than what is shown in figure 1.3 but at much

lower densities. Basin and mountain big sagebrush

are concentrated, for the most part, in southwestern

Montana. Payne (1973) published a vegetative map of

Montana based on work in the early 1940s. While his

map agrees to general distribution of big sagebrush of

the Morris and others (1976) map, the latter map

appears to have more area delineated as big sagebrush. Both maps outline greater areas of big sagebrush in Montana than regional vegetative maps

published by Bailey (1980); Küchler (1970); West

(1983a, 1988, 1996); and perhaps Aldous (1924). Possible reasons for variation among vegetative maps for

the same area will be discussed later in this section.

The distribution of big sagebrush on highly localized

vegetative maps is presented by Brown (1971) for

southeastern Montana and by Patten (1963) for the

Madison mountain range of southwestern Montana.

Figure 1.1—A regional distribution map of big sagebrush (Artemisia tridentata) by McArthur and Plummer

(1978). The solid line delimits the subgenus

Tridentatae (big sagebrush and its close relatives).

Figure 1.2—Regional map of the distribution of big

sagebrush (Artemisia tridentata) in the northern

Great Plains by Johnson (1979).

Figure 1.3—A distribution map of big sagebrush

(Artemisia tridentata) for the state of Montana by

Morris and others (1976).
10 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Distribution of big sagebrush within Wyoming is

shown in figure 1.4 (Beetle and Johnson 1982). Figure

1.4 is a representation of the distribution of all three

subspecies of big sagebrush or combination of the

maps printed on pages 38, 42, 46, and 50 of the Beetle

and Johnson (1982) publication. Big sagebrush covers

nearly the entire State of Wyoming, ranging from

5,000 to 10,500 feet elevation, and grows on a variety

of soils. As with Montana, the same regional maps

show less area of big sagebrush distribution in Wyoming than the Beetle and Johnson (1982) map. Highly

localized vegetative maps and vegetative descriptions

of northwest Wyoming have been published by Beetle

(1961); Loope and Gruell (1973); McArthur and others

(1995); and Sabinske and Knight (1978).

Figure 1.5 represents the distribution of big sagebrush in Idaho (Tisdale and others 1969). While the

authors did not distinguish between the various species of sagebrush—such as black sagebrush (Artemisia nova), low sagebrush (A. arbuscula), three-tip

sagebrush (A. tripartita), and silver sagebrush (A.

cana)— big sagebrush dominates well over two-thirds

of the sagebrush region of Idaho. Most of the sagebrush region of Idaho lies within a large arc-shaped

area called the Snake River Plain of southern Idaho.

This plain is some 360 miles long and 50 to 80 miles

wide and varies in elevation from 2,300 to 6,600 feet

(Tisdale and others 1969). Other areas in southern

Idaho that support significant stands of big sagebrush

include the Owyhee plateau southwest of the Snake

River Plain, the extension of the Basin and Range

Province east of the Owyhee plateau, the Middle

Rocky Mountain Province bordering the east side of

the Snake River Plain, and Little and Big Lost Rivers

and Birch Creek, which extend big sagebrush stands

into central Idaho (Hironaka and others 1983).

Winward and Tisdale (1977) published a map of big

sagebrush by subspecies distribution that lacks many

of the details of the Tisdale and others (1969) map, but

it gives a general idea where these subspecies can be

found. Three research reports contain big sagebrush

distribution maps for the Idaho National Engineering

and Environmental Laboratory in southeastern Idaho

(Anderson and others 1996; Atwood 1970; Harniss and

West 1973), and Piemeisel (1932) produced a distribution map of big sagebrush for an area of the Snake

River Plain called the Salmon River Tract in 1929.

I have been unable to locate a big sagebrush distribution map for Oregon; however, regional maps published by a number of researchers outline in general

terms where big sagebrush occurs (Beetle 1960; Stoms

and others 1998; West 1983a, 1988, 1996). Big sagebrush covers most of the southeastern quarter of

Oregon and extends north, essentially following the

John Day River through the center of the State, to the

Columbia River.

The geographic range of big sagebrush for Washington is illustrated in figure 1.6 (Daubenmire 1970). Big

sagebrush habitat is in central Washington starting a

few miles east of the confluence of the Snake and

Figure 1.4—A distribution map of big sagebrush (Artemisia tridentata) for the state of Wyoming by Beetle and

Johnson (1982). This map is a composite of four maps

found on pages 38, 42, 46, and 50 of the Beetle and

Johnson (1982) publication.

Figure 1.5—A distribution map of big sagebrush

(Artemisia tridentata) for the state of Idaho by Tisdale

and others (1969). The authors did not distinguish

between the various species of sagebrush, such as

black sagebrush—Artemisia nova, low sagebrush—

A. arbuscula, three-tip sagebrush—A. tripartita, and

silver sagebrush—A. cana. Big sagebrush dominates well over two-thirds of the sagebrush region of

Idaho.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 11

Columbia Rivers, west to the Cascade Range, and

north along the Columbia and Okanogan Rivers to

British Columbia, Canada. Thus, big sagebrush distribution forms a nearly continuous belt from eastern

Montana through Wyoming, Idaho, Oregon, Washington, and ending in southern British Columbia.

Big sagebrush distribution maps have been published for the States of California, Nevada, Utah,

Colorado, Arizona, and New Mexico. These are listed

in table 1.1

The amount of big sagebrush outlined on a distribution map can vary greatly among reports for a given

area. For example, Atwood (1970) delineates greater

Figure 1.6—A distribution map of big sagebrush

(Artemisia tridentata) for the state of Washington

before settlement days by Daubenmire (1970).

Table 1.1—Articles containing big sagebrush distribution maps or vegetative descriptions for the big

sagebrush States of Arizona,

California, Colorado, Idaho,

New Mexico, Nevada, Utah,

and the Western United

States.

Arizona

Hodgkinson 1989

Merkle 1952

Merkle 1962

Shreve 1942b

California

Chabot and Billings 1972

Heller 1911

Klyver 1931

Sampson and Jespersen 1963

Colorado

Baker and Kennedy 1985

Johnson 1941

Robbins 1910

Idaho

Bright 1966

Rosentreter and Kelsey 1991

Winward and Tisdale 1977

Nevada

Billings 1945

New Mexico

Wright and others 1973

Utah

Christensen 1963

Christensen and Hutchinson 1965

Cottam 1929

Fautin 1946

Kearney and others 1914

Shantz and Piemeisel 1940

Stoddart 1941

Walker and others 1996

Regional

Bailey 1896

Beetle 1960

Branson and others 1967

Everett 1985

McArthur 1994

McArthur and Ott 1996

Plummer 1974

Shreve 1942a

Shultz 1986b

Tueller and others 1979

Ward 1953

West 1983b

West and others 1998

Young and others 1990a
12 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

amounts of grass habitat on the Idaho National Engineering and Environmental Laboratory than does

Harniss and West (1973). Morris and others (1976)

classify significantly greater areas of Montana as big

sagebrush habitat than does Küchler (1970). Comparing the distribution of big sagebrush along the northern border of Wyoming (fig. 1.4; Beetle and Johnson

1982) to the southern border of Montana (fig. 1.3;

Morris and others 1976) gives the impression that

much of the big sagebrush of Wyoming stopped at the

Wyoming-Montana line, especially in the northeastern and northwestern corners of Wyoming (see black

blocks south of the Wyoming-Montana line, fig. 1.3).

Plant populations do not recognize State boundaries

and the differences seen (big sagebrush occupying 73

percent of the Wyoming-Montana line according to

Beetle and Johnson 1982, but 32 percent according to

Morris and others 1976), are due to a multitude of

reasons including: definition of what constitutes big

sagebrush habitat (modicum or dominant), whether

the workers are mapping present day, or potential, or

historic vegetation; or personal bias against big sagebrush. So it is little wonder that estimates of the

number of acres in big sagebrush habitat varies greatly

among authorities: 96.5 million to 270 million acres for

all species of woody sagebrush with big sagebrush as

the principal sagebrush (Bailey 1980; Beetle 1960;

McArthur and Ott 1996; Tisdale and others 1969).

Has Big Sagebrush Invaded Grasslands?

It has become conventional wisdom that since EuroAmerican settlement, big sagebrush has extended its

distribution and that much of present day big sagebrush dominated habitat is the end result of overgrazing (Christensen and Hutchinson 1965; Cook 1963;

Cottam and Stewart 1940; Gruell 1986; Loope and

Gruell 1973; Morris and others 1976; Reitz and Morris

1939; Stoddart 1941; Stoddart and others 1975; Weaver

and Alberston 1956). Stoddart and others (1975, p. 34)

stated: “Great uncertainty exists as to exact original

extent of the bunchgrasses since, with overgrazing,

sagebrush has invaded the intermountain grasslands

from the south. Some ecologists hold that much of

southern Idaho, eastern Washington, eastern Oregon,

western Montana, and large areas of northern Nevada

and Utah are climax grassland.” Cook (1963, p. 190)

said: “It has invaded millions of acres of deteriorated

foothill range in the intermountain area.”

However, Tisdale and others (1969), studying historical records and undisturbed or ungrazed sites,

concluded that the geographic distribution of woody

species of sagebrush is the same today as in

presettlement times. Daubenmire (1970, p. 83) noted:

“In Washington, there is no evidence to support claims

that Artemisia tridentata and Opuntia polycantha

have increased their ranges since the advent of white

man. In fact, the range of Artemisia tridentata may

have been reduced by promiscuous burning during the

early period of settlement in Washington.” Hironaka

(1979, p. 29) agrees and further noted: “The numerous

species and subspecies of Artemisia that occur in

relatively monospecific stands indicate that they are

well adapted to the habitats they presently occupy—

strong evidence that adaptation was established well

before the advent of livestock grazing in the west.”

There is another biological factor that supports the

proposition that big sagebrush has not invaded grasslands; this one deals with the manner in which achenes

or seeds are dispersed. Pendleton and others (1989)

classified the dispersal mechanism of big sagebrush as

microwind, meaning that the achenes lack any type of

structure that would allow them to float or travel any

great distances in wind currents (see also Young

1983). Chambers (2000) noted that seeds lacking appendages but with small surface areas, such as with

big sagebrush, do not experience significant horizontal movement. Several workers have estimated maximum distance of achene dispersal of less than 100 feet

from the mother big sagebrush plant (Astroth and

Frischknecht 1984; Daubenmire 1975; Frischknecht

1979; Johnson and Payne 1968; Walton and others

1986; Wambolt and others 1989; Welch 2000, unpublished data on file at the Shrub Sciences Laboratory,

Provo, UT; Young and others 1990b). If it takes from 2

to 4 years for a big sagebrush plant to reach maturity,

then big sagebrush would spread from 25 to 50 feet per

year, or in other words, it would take big sagebrush

about 105 to 211 years to spread 1 mile. In the case of

the Snake River Plain of southern Idaho, which varies

from 50 to 80 miles wide, it would take big sagebrush

some 5,250 to 16,880 years to distribute itself across

the entire plain— that is going from south to north;

this is in accordance with Stoddart and others (1975)

earlier statements concerning sagebrush invasion from

the south.

Biological factors and historical and fossil records do

not support the contentions that big sagebrush invaded grasslands of the West. The only exceptions are

highly localized, wet areas where high water tables

had previously excluded big sagebrush but, through

draining, created an environment where big sagebrush could grow (Cottam 1929; Cottam and Stewart

1940). Beetle and Johnson (1982, p. 6) put it in these

simple terms: “sagebrush is where sagebrush was.”

Relationship Between Grazing

and Big Sagebrush Canopy

Cover _________________________

It has been a biological principle, or axiom, that due

to overgrazing, big sagebrush has increased in den-
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 13

sity, or as I would term it, in canopy cover (McArthur

and others 1995). Miller and others (1994, p. 115) state

it best:

In the early to mid 1800s much of the sagebrush steppe

was probably composed of open stands of shrubs with a

strong component of long-lived perennial grasses and

forbs in the understory. Shrub canopy cover probably

ranged between 5-10% in the drier Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) communities (Cooper 1953; Young et al. 1976; Winward

1991), to 10-20% on the more mesic sites, occupied by

mountain big sagebrush (Tisdale et al. 1965; Winward

1991).

Speaking of the present, they noted “Wyoming big

sagebrush cover has increased from less than 10% to

20%, and mountain big sagebrush cover from less than

20% to 30 and 40% (Winward 1991)” due to overgrazing. Although, Frischknecht and Harris (1973) reported that fall grazing by sheep decreased the size of

big sagebrush plants and greatly reduced the production of flower stalks. This would reduce, not increase

the canopy cover of big sagebrush on a given site.

When I began writing of this report I did not envision

challenging this concept, especially after reading and

studying Tisdale and others (1965) report on their

vegetative analysis of the ungrazed Carey kipuka

(located 14 miles east of Carey, ID). (A kipuka is an

area of older land or soil surrounded by later lava

flows.) They reported big sagebrush canopy cover of 13

percent, although in their photograph of the kipuka

(their fig. 2), the canopy cover of big sagebrush appears

to be a little more than 13 percent. It wasn’t until I read

and studied the Passey and Hugie (1963a) report,

particularly the photograph of their study site, which

was a kipuka located some 20 miles southwest of

Aberdeen, ID, that I felt perhaps this concept might

not be valid. It is clear from the photograph that big

sagebrush canopy cover exceeded, at this ungrazed

kipuka, the 20 percent upper limit proposed by Miller

and others (1994), Baxter (1996), and Winward (1991).

I believe this principle, then, is invalid based on

three reasons: first, what do the animals that coevolved with big sagebrush suggest to us concerning

canopy cover; second, what are the big sagebrush

canopy cover values found in undisturbed relicts such

as kipukas; and third, what is the quality of the science

that is used to support this principle (Welch and

Criddle 2003)?

Numerous studies (see Peterson 1995 and chapter II

for a review) show animals of big sagebrush prefer

living in big sagebrush canopy cover far above the 20

percent upper limit (Baxter 1996; Miller and others

1994; Winward 1991). In fact, Rasmussen and Griner

(1938) noted that the highest sage grouse nesting

success in Strawberry Valley of central Utah occurred

in mountain big sagebrush stands having 50 percent

canopy cover. They estimated that some 270 acres of

big sagebrush habitat was in the 50 percent canopy

cover class. Ellis and others (1989) reported male sage

grouse loafing in areas with 31 percent big sagebrush

canopy cover. In addition, Katzner and Parker (1997)

reported that areas of high pygmy rabbit (Brachylagus

idahoenesis) activity occurred in basin big sagebrush

stands having 51.1 percent canopy cover, and areas of

medium activity occurred in Wyoming big sagebrush

stands of 42.7 percent canopy cover.

Still, other sagebrush obligates such as sage thrasher

(Oreoscoptes montanus), Brewer’s sparrow (Spizella

breweri breweri), and sage sparrow (Amphispiza belli)

prefer big sagebrush canopy cover of 20 to 36 percent,

which is much higher than the 20 percent maximum

cover of the axiom (Best 1972; Feist 1968; Grinnell and

others 1930; Knick and Rotenberry 1995; Petersen

and Best 1986, 1991; Reynolds and Trost 1980, 1981;

Rich 1985; Winter and Best 1985). For sagebrush

species other than big sagebrush, Walcheck (1970)

reported that a population of Brewer’s sparrows were

living in an area of silver sagebrush having a canopy

cover of 53 percent. Petersen and Best (1985), studying nest site selection of sage sparrows, found that

these birds nested where (probably Wyoming) big

sagebrush canopy cover was 23 percent in the vicinity

of nests. Further, they noted that all nests were

situated in big sagebrush plants and that large, living

shrubs were strongly preferred. Rotenberry (1980)

found greater numbers of sage sparrow and western

meadowlark (Sturnella neglecta) on sites where (probably Wyoming) big sagebrush canopy covers ranged

from 25 to 30 percent than on sites with big sagebrush

canopy cover of 0 to1 percent and 5 to10 percent. Short

(1984) reported that shrub canopy, mostly big sagebrush, had to exceed 30 percent in order to achieve a

habitat suitability index of one for Brewer’s sparrows.

Also, Best (1972) and Feist (1968) found greater numbers of Brewer’s sparrow and sage thrashers in stands

of (probably Wyoming) big sagebrush with canopy

cover at 36 percent than at 21 percent.

Big sagebrush canopy cover measured on undisturbed relicts and kipukas does not support the axiom

that big sagebrush canopy cover increased due to

overgrazing. Daubenmire (1970, p. 1) reported that

big sagebrush canopy cover varied on his “virgin or

near virgin vegetation” study sites from 5 to 38 percent. The technique used by Daubenmire (1970) tended

to underestimate shrub canopy cover by 3 to 5 percentage points according to an analysis by Floyd and

Anderson (1987). Baker and Kennedy (1985) reported

that canopy cover of Wyoming big sagebrush remnant

stands varied from 8 to 20 percent.

I have measured, using the line intercept method

(300 feet), the canopy cover of big sagebrush in four

ungrazed kipukas and found that canopy cover ranged

from 14 to 34 percent (see chapter IV for details), or in

other words, from 66 to 86 percent of the area’s surface was
14 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

occupied by something else other than big sagebrush.

Basin big sagebrush was the dominant big sagebrush

in two of the kipukas, one about 20 miles west of Idaho

Falls, ID, and the other about 14 miles east of Carey,

ID. On the first kipuka, big sagebrush canopy cover

was 14, 16, and 23 percent for the three 300-foot line

intercept transects. These measurements would support the axiom for mountain big sagebrush but not for

Wyoming big sagebrush (big sagebrush on this kipuka

was basin). A high percentage of the big sagebrush

plants had been killed by defoliators, thus reducing

live canopy cover to the values given. Big sagebrush

canopy cover values were based on live canopy cover

intercepted. Had I included, as the USDA Forest

Service Handbook recommends (Goodrich and Huber

2001; USDA Forest Service 1993), portions of dead

stems, the canopy cover values would have been higher.

Along the transects there were numerous big sagebrush seedlings, enough to replace the dead and near

dead big sagebrush plants, to the point of a full recovery of canopy cover well above what I measured. Big

sagebrush canopy cover values measured on the Carey,

ID, kipuka were 26, 30, and 34 percent. There were no

signs of defoliators at work. The differences between

my measurements and those of Tisdale and others

(1965) are difficult to explain; perhaps they took their

measurements in areas heavily dominated with threetip sagebrush, which occurs on the east side of the

kipuka. My measurements were taken in the center of

the kipuka.

For the two kipuka dominated by Wyoming big

sagebrush west of American Falls, ID, Wyoming big

sagebrush canopy cover values were 14, 23, and 28

percent and 20, 24, and 31 percent. The work done by

Daubenmire (1970), Baker and Kennedy (1985), and

me (kipuka measurements June 2000) apparently

does not support the idea that mountain big sagebrush

does not naturally exceed 20 percent canopy cover and

Wyoming big sagebrush, 10 percent.

According to West (1999, p. 16), concerning kipukas

or relicts: “These relicts are not completely reliable as

reference conditions because they are incomplete ecosystems.” I believe they are the best reference areas

available. West was a coauthor of Miller and others

(1994) report that cites Tisdale and others (1965) to

support their assertion that big sagebrush canopy

does not naturally exceed 10 or 20 percent. Tisdale and

others (1965) collected their data from the Carey

kipuka.

For the kipukas I visited, there seemed to be the

usual complement of birds, small mammals, reptiles,

insects, spiders, lichens, shrubs, grasses, forbs, and

biological crusts. On one kipuka I observed deer

tracks. For the kipuka that Passey and Hugie (1963b,

p. 114) studied, they noted: “Deer and antelope occasionally cross the kipuka and there is evidence of a

small rodent population.” Because these kipukas are

surrounded by lava flows, the fire return intervals are

probably much longer than for nearby big sagebrush

stands outside the kipukas. Even though kipukas are

small, they represent the best references of pristine

big sagebrush stands.

Holechek and Stephenson (1983) found that big

sagebrush canopy cover was higher inside the exclosure

on their upland study site and higher on the outside of

their exclosure on their lowland site. This means that

grazing decreased big sagebrush canopy cover outside

of the exclosure in the upland site and increased it for

the lowland site. Eckeret and Spencer (1986) also

reported inconsistences concerning big sagebrush cover

response to grazing. Pearson (1965), studying vegetative production in grazed and ungrazed plant communities, found that big sagebrush canopy cover in the

ungrazed area was 34 percent and perennial grasses

39 percent compared to 11 percent big sagebrush

canopy cover in the grazed area with 22 percent

perennial grass cover. Similarly, Anderson and Holte

(1981) reported that for an area in southeastern Idaho

protected from grazing for more than 25 years, big

sagebrush canopy cover increased from15 to 23 percent with an increase in grass cover from 0.28 to 5.8

percent. Wambolt and Watts (1996, p. 148) noted that:

“heavy stocking rates reduce sagebrush cover primarily through mechanical damage, but some browsing

was observed”; and they added that: “The exclusion of

grazing for 30 years had no effect on [Wyoming big]

sagebrush canopy [13.5 percent] in untreated plots.”

Yet in their treated plots, Wyoming big sagebrush

canopy cover increased over time to canopy cover

values of 19 percent (plowed and seeded), 17 percent

(chemical spray), 14 percent (rotocut), and 11 percent

(burn) in the absence of grazing. Muscha and others

(2004, p. 181) observed: “Our data demonstrate shrub

cover will not always increase where stock are excluded at a greater rate then with livestock present. It

is clear that the release of grazing pressure does not

decrease shrub canopy; in some cases it may allow

shrub canopy to increase [5 out of 9 increase; 2 out of

9 decrease; 2 out of 9 stayed the same]”. Lusby (1970)

noted for all sites, including the big sagebrush site, a

decrease in shrub overstory as a result of livestock

grazing. Last, Johnston (2003) listed three data sets

that would in his own words “deny the axiom.” These

studies show that grazing may or may not increase big

sagebrush canopy cover, or in other words, no general

relationship exists between grazing and big sagebrush

canopy cover.

Peterson (1995) noted greater big sagebrush cover

inside of an exclosure than outside due to heavy wild

ungulate grazing. Wambolt and Sherwood (1999) found

an average of three times as much big sagebrush

canopy cover inside exclosures at 19 sites across the
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 15

northern Yellowstone winter range as outside. Wild

ungulate grazing decreases big sagebrush canopy cover.

The following articles are often cited to support the

range management axiom that big sagebrush canopy

cover increased above natural levels due to overgrazing: Blaisdell (1949); Blaisdell and others (1982); Clark

(1981); Cooper (1953); Hanson and Stoddart (1940);

Laycock (1978); Pickford (1932); Robertson (1947;)

Stoddart (1941); Tisdale and others (1965); Winward

(1991); Wright and Wright (1948); Young (1943); and

Young and others (1976). These reports can be classified, in my opinion, into two classes: those based on

opinion or experience and those that are data based

but with questionable applicability. An example of

the first is Laycock’s (1978, p. 232) statement:

“Overgrazing has resulted in dense stands of sagebrush with little herbaceous understory in many areas.” This statement is not supported by citations, or

data, but is given as a statement of principle. There

may well be little herbaceous understory, but invoking

overgrazing as a cause of dense stands of sagebrush is

not supported. Other citations that fall into the statements of faith are: Blaisdell and others (1982); Clark

(1981); Stoddart (1941); Winward (1991); and Young

and others (1976). The remaining articles or citations

contain scientific data but I question their applicability. One study (Young 1943) was conducted on non-big

sagebrush sites within the Palouse grassland of eastern Washington and northern Idaho; another one was

concerned with the impact of grazing on the root

system of grasses (Hanson and Stoddart 1940). Two

were studies concerned with competition between big

sagebrush and grasses (Blaisdell 1949; Robertson

1947); another study (Pickford 1932) used ocular estimates. One study was conducted in the transition

zones between shrublands and grasslands of Montana

(Wright and Wright 1948). Cooper (1953) expressed

his data in percent composition, which would vary

according to amount of grasses and forbs removed by

grazing or reduced by drought; and I discussed the two

remaining studies (Daubenmire 1970; Tisdale and

others 1965) earlier.

How Much of the Big Sagebrush

Ecosystem is Left? ______________

Euro-American settlers soon discovered that the presence of “big” big sagebrush was a good indicator of soils

that were well suited for agricultural pursuits

(Clements 1920; Fireman and Hayward 1952; Poulson

1946; Thatcher 1959). The result was that the big

sagebrush ecosystem has been shrinking since the

first Euro-Americans decided to settle in big sagebrush country. Upon arriving, the first task was to

clear big sagebrush to make room for gardens, building sites, fields, orchards, corrals, and so on. Then

later, the building of reservoirs, highways, towns,

cities, and the practice of range management contributed to the shrinking of big sagebrush ecosystem.

Now an alien annual grass, cheatgrass (Bromus

tectorum)—a dry, prickly grass—has invaded the big

sagebrush ecosystem and has increased fire frequency

about 12 to 22 times (Whisenant 1990), resulting in an

ecosystem changed to the point that some believe the

system is endangered. Knick’s (1999) article on this

subject—“Requiem for a Sagebrush Ecosystem?”—

shares my concerns over the practice of fuels management, developed in the forestry systems, being applied

in big sagebrush ecosystems (Winward 1984, 1991).

He estimates that about 30 percent of the big sagebrush ecosystem is left in the Snake River Birds of

Prey National Conservation Area of southwestern

Idaho, and what is left is highly fragmented (also see

Knick and Rotenberry 1997).

For the State of Washington, Dobler (1994) estimated that 41 percent of the original shrub-steppe

remains, or in other words, 59 percent has been converted to agriculture, development, or water storage.

I estimated that 48 percent of the big sagebrush

habitat in Washington remains, as determined by

superimposing Daubenmire’s (1970) vegetation zones

map onto the land cover map for the State of Washington developed by Cassidy (1997). Each proportional

area (sagebrush habitat, agricultural lands, cities,

towns, water storage, and so on) was determined by

cutting it from the maps and weighing each area

within the former big sagebrush habitat. From these

figures, I calculated that 48 percent of the big sagebrush remained.

Effects before and after Euro-Americans on big sagebrush ecosystems in the State of Washington are

illustrated in figures 1.6 before, and 1.7 after; note the

great amount of fragmentation. Of course, only the

most productive big sagebrush sites (deep soils and

highly fertile) were developed for agricultural use,

leaving big sagebrush growing on less fertile and

shallow soils, steep unusable hillside, or suitable sites

not yet developed. The largest areas of big sagebrush

stands in Washington are the Hanford Reservation

(infested with cheatgrass) and the Yakima Firing

Range (Cassidy 1997; Welch’s personal observation in

June of 2000).

Life Expectancy _________________

Pool (1908) described the big sagebrush he studied

at Fort Garland, CO, as being 50 years old. For the

Escalante Valley near Milford, UT, Shantz and

Piemeisel (1940) found 45-year-old big sagebrush

plants in a big sagebrush-greasewood community.

Lommasson (1948), studying succession in a big sagebrush stand growing on the Beaverhead National
16 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Forest in southwestern Montana, noted the average

age of big sagebrush plants was 61 years. Ferguson

and Humphrey (1959, p. 3) stated: “This study has

shown that [big] sagebrush produces a growth ring

that is sensitive to changes in annual precipitation

and sometimes reaches an age of slightly more than

200 years.” In a series of studies by Passey and Hugie

(1962, 1963a,b) conducted on relicts and ungrazed

kipukas of eastern and southern Idaho, northern Utah,

and northeastern Nevada, they found that the age of

big sagebrush plants varied from 27 to 120 years.

Ferguson (1964), in an extensive study that included

700 samples from areas of northwestern New Mexico,

northeastern Arizona, the San Bernardino and

Panamint Mountains of California, and White mountains of California and Nevada, found that the age of

big sagebrush plants varied from 22 to 216 years.

Schneegas and Nord (1967) estimated the age of a

large big sagebrush plant found in the White Mountain of eastern California to be 50 to 60 years old.

Fowler and Helvey (1974) found, on their study site in

the Columbia River Basin of Washington, the maximum age of big sagebrush plants is less than 100

years. Wambolt and Hoffman (2001) reported that

mountain big sagebrush plants growing in southwestern Montana ranged in age from 5 to 109 years.

Perryman and others (2001) reported, for their study,

a maximum age of 81 years for mountain big sagebrush, 75 years for Wyoming big sagebrush, and 55

years for basin big sagebrush. Daubenmire (1975)

reported maximum age of big sagebrush plants in

Washington to be 95 years. Thus it appears, in humanistic terms, big sagebrush is a long-lived plant but

shorter lived when compared to some plant species.

Morphology and Anatomy ________

Three classic studies have described the general

morphological and anatomical characteristics of big

sagebrush (Diettert 1938; Pool 1908; Ward 1953). Of

these three, perhaps Diettert (1938) is the most comprehensive and will be referenced extensively in this

section. Gross morphological characteristics of the

three subspecies of big sagebrush will be given in the

taxonomy section of this chapter.

Inflorescence Versus Vegetative Branches

Branches or shoots of big sagebrush are of two

types—vegetative and reproductive, or inflorescence—

which not only appear different externally but also

internally (Diettert 1938; Ward 1953). Growth of vegetative branches starts in early spring and stops in

early summer, whereas inflorescences start in late

spring and terminate growth in late summer (Miller

and others 1986). Vegetative branches are perennial

in nature, whereas inflorescences are annual; in other

words, their growth is determinate in nature and they

die upon maturation of fruits or achenes. Leaves of

vegetative branches are all tridentate or multiple

lobes, but only the lower leaves of inflorescences are

tridentate; the upper and majority of leaves are entire

or nonlobed (plate I, fig. 3). All inflorescences shed

their leaves before maturity, whereas vegetative

branches retain about a third of their leaves throughout late summer, fall, and winter (Miller and Shultz

1987). Both kinds of branches are covered by thick

layers of trichomes or hairs (plate X), the removal of

which reveals that both are distinctly striated. Structure of trichomes will be discussed later in the leaf

section. Inflorescences develop large, loose to dense

panicles, with sessile heads containing from three to

Figure 1.7—A distribution map of big sagebrush

(Artemisia tridentata) for the state of Washington

after settlement days by Cassidy (1997).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 17

seven flower heads or clusters (plate I, fig. 3). Internally, inflorescences differ from vegetative branches

by the presence of chlorenchyma beneath the epidermis, by earlier and more extensive development of

fibers in both the xylem and pericycle, and by becoming more slender and less rigid than the vegetative

branches. But as the inflorescences reach maturity

they become harder due to the production of sclerenchyma tissue.

Floral Development

Flower heads or clusters are ovoid to campanulate in

shape and are small, being 3.0 to 4.5 mm by 2.0 to 3.5

mm at maturity (plate I, fig. 1 and 2). Diettert (1938)

reported two types of involucral bracts for big sagebrush flower heads: the outer shorter, orbicular-ovate

varying in number from four to nine, and the much

longer, elliptic-spathulate inner involucral bracts numbering six to nine (plate I, fig. 1 and 2). The first flower

part to differentiate is the corolla, followed by the

stamens, and then the pistil (plate I, fig. 4 through 10).

Pappus, a tuftlike appendage of the achene, is lacking;

also lacking is any evidence of a calyx (plate I, fig. 11,

12, and 14). However, Daubenmire (1975), citing a

Ph.D. degree dissertation, describes the presence of a

calyx tube that “breaks away from the rest of the

corolla.” Daubenmire’s (1975) use of “calyx tube” is

probably incorrect. The term “corolla tube” instead

would have been better. During the early development

of the corolla “tube,” the lobes or tips curve inward and

their marginal cells become papillated, interlock, and

fused, thus sealing the flowers until forced open by

enlarging stamens (plate I, fig. 11 through 14). Development of pollen and embryo sac of big sagebrush is

typical of dicotyledonpus plants; for details the reader

is referred to Diettert (1938).

Embryo, Seed Development, and Anatomy

After double fertilization, the zygote increases in

size and then divides transversely resulting in a large

basal cell (b) and a smaller apical cell (a), and at the

same time first division of the primary endosperm

nucleus occurs (plate V, fig. 60 and 61). Continued

development of the embryo is described by Diettert

(1938, p. 9):

The next division is also transverse, the basal cell

dividing to form a somewhat flattened middle cell

(plate V.62-m). The vertical division of the apical cell

occurs at approximately the same time (plate V.63),

and further divisions of these cells give rise to the

cotyledons and plumule (plate V.64-71). The basal cell

(b) may divide transversely before the middle cell (m)

divides vertically (plate V.65), or the order of the divisions of these two cells may be reversed (plate V.66).

The divisions of the middle cell (m) ultimately produce

in part the hypocotyledonary portion of the embryo and

the basal cell (b) completes this region and forms the

suspensor (plate V.67-71). The latter never consists of

more than two or three cells which remain small and

soon disappear (plate V.71, 74).

During this period, the cells of the endosperm are

dividing forming a multicellular endosperm that for a

time is far in advance of the embryo, but eventually the

embryo enlarges to the point that, in a nearly mature

seed, the endosperm forms a thin layer around the

entire embryo (plate V, fig. 72 through 75). The point

where the mature achene separates from the rest of

the corolla tube is smooth as pictured in plate V, figure

75. However, Daubenmire (1975) describes this area

as containing a small bur-like structure. In all of the

seed lots of big sagebrush that I have inspected, I have

never observed any structure that I would call a small

bur attached to or part of achenes.

Leaf Anatomy and Development

Leaves in big sagebrush start out as a series of

periclinal divisions within the second and third layers

of the tunica (plate VI, fig. 76), which leads to development of a papillate protuberance near the shoot apex

(plate VI, fig. 77), the leaf primordium. This differentiates into a five-layered structure (plate VI, fig. 77

through 80a), of which the outer layers differentiate

into upper and lower epidermis with the next two

layers developing into palisade tissue and the central

layer into veins and spongy mesophyll. Some epidermal cells start to differentiate early in the development of leaves into trichomes (plate VI, fig. 78). During

the early differentiation of big sagebrush leaves, a

greater rate of cellular division occurs on the abaxial

side than adaxial side of the margins of the developing

leaf; thus, the margins turn inward giving the structure a U-shaped appearance in cross section (plate VI,

fig. 85). Plate VII, figures 87 through 90; plate VIII,

figures 91and 92; and plate IX, figures 93 through 98

illustrate the development of veins, spongy mesophyll,

palisade layers, intercellular spaces, and epidermal

layers.

Plate X, figures 99 through 119 represent the development of trichomes on big sagebrush leaves. Trichomes of big sagebrush are of two types, glandular

(plate X, fig. 99) and nonglandular (plate X, fig. 109),

and are distinguishable from each other at an early

stage of differentiation (plate X, fig.100 and 111) with

the glandular trichomes somewhat in advance of the

nonglandular trichomes. Both are derived from epidermal cells (Pool 1908). Diettert (1938, p. 24) describes the development of glandular trichomes:

Development of the glandular hairs begins with an

anticlinal division of a slightly protruding epidermal

cell (plate X.101). This division always occurs in the

direction parallel to the transverse plane of the leaf.

Following this first division the two daughter cells

elongate and enlarge considerably and divide

periclinally. The two protruding cells then undergo a
18 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

series of periclinal divisions, giving rise to eight cells

(plate X.102 through 105, 99). The mature trichomes,

without exception, are composed of ten cells, including

the two basal cells (plate X.99).

The differentiation of nonglandular T, or cover trichomes (Pool 1908), from epidermal cells is in striking

contrast to that of glandular trichomes. First of all, the

beginning is recognizable by the elongation and protrusion of a single epidermal cell (plate X, fig. 111

through 113), which divides periclinally, producing an

apical cell that does not divide but begins to elongate

laterally in two directions in the longitudinal plane of

the leaf; hence, forming a T-shaped structure (plate X,

fig. 114 through 119). The base cell divides periclinally

a number of times to form the stalk of the T (plate X,

fig. 116 through 119, and 109 and 110). Diettert (1938,

p. 25) observed, “The numerous nonglandular trichomes with stalks of various lengths and with long

intertwining apical cells form a dense hairy covering

approximately 200 microns thick over the entire surface of the leaf (plate X, fig 119).”

Mature leaves of big sagebrush are usually tridentate. Considerable variability does occur on a single

plant from entire or nonlobed to some with as many as

eight or more lobes (plate IX, fig. 98; Marchand and

others 1966). They are more or less wedge-shaped,

tapering gradually from the wide tip to the narrow

petiole-like base, which broadens out a little near the

point of attachment. Big sagebrush leaves are spirally

arranged on the stem with a 2/5 divergence (Diettert

1938; Ward 1953). Diettert (1938, p. 19) noted: “The

internodes are often so short that the leaves form

dense, rosette-like clusters at the stem tips, a feature

especially evident in plants living in less favorable

places.” He is probably describing leaves of Wyoming

big sagebrush. He further observed that leaves produced in the early summer (Marchand and others

1966; plate IX, fig. 98 j, l, n) are larger than those

produced later in the summer; or in other words, leaf

development in big sagebrush is dimorphic, that is two

kinds of leaves (ephemeral and persistent) are produced during the coarse of the growing season (Branson

and others 1976; Daubenmire 1975; Link and others

1995; Marchand and others 1966; McDonough and

others 1975; Miller and others 1983, 1986; Miller and

Shultz 1987; Ward 1953).

Big sagebrush plants start the growing season (early

spring) with just persistent leaves that were formed

during the pervious growing season; however, early in

the current growing season large ephemeral leaves

develop (Miller and Shultz 1987). After the first crop of

ephemeral leaves have matured, a second crop of

smaller ephemeral leaves and persistent leaves start

to develop in the axes of the mature ephemeral leaves

producing what is termed a short shoot. There are, at

this point, actually four kinds of leaves: first, the

persistent leaves that overwintered; second, large

mature ephemeral leaves; third, secondary ephemeral

leaves developing on short shoots; and fourth, a current crop of persistent leaves also developing on short

shoots. Ephemeral leaves on inflorescences are not

born on short shoots.

Miller and Shultz (1987) noted that persistent leaves

live a total of 12 to 13 months. Miller and Shultz (1987,

p. 228) described the longevity of big sagebrush leaves:

“At the onset of drought, both the previous season

perennial and large, early-developing ephemeral leaves

begin to senesce. Later-developing ephemerals, including nonlobed leaves, persist during the initial

phase of leaf fall, senescing in late summer and fall. By

November only the current crop of perennial leaves

persists.” They estimated that big sagebrush maintained 33 percent of their leaves in the winter. Branson

and others (1976) estimated less than 20 percent.

Anatomy of mature big sagebrush leaves is unilateral and consists of upper and lower epidermal layers,

an adaxial and abaxial palisade, and a central region

of spongy mesophyll and veins (plate IX, fig. 93). The

two epidermis layers are similar in structure with

many cells differentiating into trichomes, which provide a dense covering over the leaves and give big

sagebrush its silvery appearance (Pool 1908; Shultz

1986a). Stomata are evenly distributed over both

epidermal layers and are somewhat raised (plates

VIII, fig. 91a; IX, fig. 96; Pool 1908). Cuticle covering

over the epidermal cells is, as compared to other plants

species, thin. Maximum cuticle thickness occurs in the

region of the midrib and larger veins, which are less

densely covered with trichomes (Diettert 1938).

Stem Anatomy and Development

Two distinguishing characteristics of big sagebrush

stems and branches are the evergreen foliage and the

absence of winter buds. The difference between vegetative and inflorescence stems has been discussed

earlier.

Vegetative stems are conspicuously eccentric in shape

(Ferguson and Humphrey 1959). This eccentricity is

caused by three factors: (1) the death of inflorescences

that results in the formation of numerous depressions

(plate XVI, fig. 145 a, b, c); (2) the destruction of the

cambium when exposed through the removal of protective bark tissues (plate XVI, fig. 145 d, e, f); and (3) the

uneven growth of the annual rings themselves, which

can vary from a few hundred microns to several millimeters in thickness within a given growth ring (plate

XVI, fig. 145). In spite of stem eccentricity, a number

of workers have used width of big sagebrush annual

growth rings as predictors of past precipitation and,

perhaps, herbage production (Ferguson and Humphrey

1959; Fowler and Helvey 1974; McGinnies 1967).

Bark of mature stems is soft, stringy-like material

that is easily removed or peeled off in narrow strips
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 19

due to the intermixing of cork and sclerenchyma tissues with weak, thin-walled phloem cells. Removal of

the bark exposes the cambium and results in its death;

normally this is localized along the stems and does not

result in the death of the entire plant.

Big sagebrush produces two kinds or types of stems

or shoots: long shoots and short shoots (Bilbrough and

Richards 1991). Because leader long shoots grow longer

than lateral long shoots, big sagebrush has a linear,

excurrent growth form. Vegetative growth starts in

early spring from terminal and lateral soft buds.

Current season long shoots produce ephemeral leaves

that die in mid to late summer. Short shoots arise

sylleptically from axillary soft buds and produce persistent or overwintering leaves that die the following

spring (Bilbrough and Richards 1991; Miller and Shultz

1987). Inflorescences are produced from short shoots,

terminal soft buds at the distal end of 1-year-old long

shoots; therefore, browsing of current year, long shoots

will reduce seed production (Bilbrough and Richards

1991; Rodriguez and Welch 1989; Wagstaff and Welch

1990, 1991). However, this allows inflorescences to be

elevated, which enhances wind pollination. One-yearold leader long shoots produce more new long shoots

and inflorescences than 1-year-old lateral long shoots,

making big sagebrush less tolerant of browsing than

many other shrub species (Bilbrough and Richards

1991; Wandera and others 1992).

Big sagebrush produces a diffuse porous wood whose

vessels in the spring wood are more numerous but

smaller in diameter than the vessels in the summer

wood (plate XVIII, fig. 152 and 153). Both spring and

summer vessels, lateral walls contain numerous pits.

Fibers in summer wood are more numerous and thicker

walled than spring wood (Fowler and Helvey 1974).

Fowler and Helvey (1974) noted that summer wood is

denser, contains more cells per unit of surface than

spring wood, and is darker in color than spring wood.

Diettert (1938, p. 38) noted: “The maturation of the

vessels is rapid, while the development of the fibers is

much slower, many of them not reaching maturity

until the following year.” For this reason the latest

annual ring has a lighter appearance and stains less

densely than the older rings (plate XVI, fig. 145).

Characteristic of big sagebrush and other sagebrush

species stems is the annual development of interxylary

cork layers, some two to 18 cells thick, between new

annual growth ring and last year’s growth ring (plates

XVI, fig. 146 and 147; and XVIII. fig. 154 and 155; Dale

1968). A single layer of cells, the interxylary cork

cambium, develops between the new annual growth

ring and last year’s growth ring (plate XX, fig. 160 and

161). This cambium starts to divide and give rise to a

multiple cellular layer (plate XX, fig. 162) that remains undifferentiated until early summer when the

innermost layers begin to mature and suberize. This

maturation and suberization continues in a centrifugal direction until midsummer when all cells in the

layer have become suberized and dead (plate XX, fig.

163). To complete the sealing of new wood from old

wood, rays are too suberized from the innermost ray

cells outward (plate XVIII, fig. 155). The observations

of Diettert (1938) were extended by Moss (1940). Moss

(1940, p. 764) noted, “The cork extends into the base of

the current year’s stem, forming there a dome-shaped

or somewhat bulbous barrier of considerable thickness and enclosing a core of closely compacted, contorted, thick-walled cells.” Moss (1940) found that the

interxylary cork extended into the root system of big

sagebrush to a distance of 6 to 8 cm from the base of

lateral roots. Possible biological functions of the

interxylary cork layer are strengthening stem bases,

protection against desiccation, protection against

pathogenic organisms, and protection against deleterious effect associated with the annual dying of inflorescences (Diettert 1938; Moss 1940). Moss (1940, p.

765), on the function of this layer noted: “Thus,

interxylary cork may account in large part for the

persistence of the sagebrush in arid regions.”

Root Morphology

Robertson and others (1972) described big sagebrush as a phreatophyte, that is, a deep-rooted plant

that can meets some of its water needs from the water

table or from a layer of soil just above the water table.

In soils without restricting layers, root depths for

basin big sagebrush have been recorded as deep as 10

to 15 feet (Daubenmire 1975; Kearney and others

1914). For mountain and Wyoming big sagebrush,

depths from 5 to 8 feet have been reported (Daddy and

others 1988; Manning and Groeneveld 1990; Reynolds

and Fraley 1989; Sturges 1977, 1979; Welch 1997).

The tap root of individual big sagebrush plants are not

necessarily the deepest. Often, the deepest roots are

branches (lateral roots) of the tap root (Manning and

Groeneveld 1990; Sturges 1977). Not only does big

sagebrush produce a deep root system, but just under

the soil surface lateral roots branch off the tap root

forming a vast root network; the majority of the root

system occurs just 12 inches under the soil surface

(Daddy and others 1988; Dobrowolski and others 1990;

Flanagan and others 1992; Manning and Groeneveld

1990; Sturges 1979). These shallow roots not only

absorb water that accumulates in the upper soil layers

during winter and spring, but can also make use of

infrequent moisture from summer convective storms

(Donovan and Ehleringer 1994). Some of these lateral

roots extend out from mature plants a distance of 3 to

5 feet before growing deeper into the soil profile

(Dobrowolski and others 1990; Reynolds and Fraley

1989; Sturges 1977; Welch 1997). Abbott and others
20 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

(1991) found that rooting depth of big sagebrush was

more dependent on soil moisture than soil disturbance.

Tabler (1964) found that root depth in mountain big

sagebrush was deeper on the drier ridge and westexposure sites as compared to the moister valley

bottom and east-exposure sites. Thus, big sagebrush

develops a two-tiered root system of dense root network at the soil surface and a deep system with tap

root or extending laterals; the diffuse root system of

big sagebrush is much greater than the taproot system

(Caldwell and Fernandez 1975; Tabler 1964).

Root growth begins in the early spring a few days

before shoot or stem growth and continues through the

late fall (Caldwell 1979; Caldwell and Fernandez 1975;

Eissenstat and Caldwell 1988; Fernandez and Caldwell

1975; Robertson 1943; Sturges 1979). Caldwell and

Fernandez (1975) observed that individual root elements may undergo growth and development for only

2 weeks or less, but the entire root system is active for

most of the year.

Through experimentation with a radioactive isotope

of iodine, Daubenmire (1975) reported that the isotope

absorbed by one section of the root system was found

only in one discrete section of the crown. Thus, it

appears that individual components of the root systems are linked to specific sections of the crown. This

supports earlier findings of Cook and Stoddart (1960)

who observed that twigs clipped on half of a big

sagebrush plant resulted in the death of the root

system on the same half. Lunt and others (1973) found

that the oxygen requirement of big sagebrush roots is

unusually high, 0.50 mg cm-2 min-1 to sustain a 50

percent maximum root growth rate. This compares to

0.30 for many economic plant species and for bur-sage

(Franseria dumosa) (Lunt and others 1973).

Soils of Big Sagebrush ___________

Big sagebrush grows on a variety of soils throughout

its range. This is illustrated in table 1.2, which lists the

Table 1.2—Soils of big sagebrush according to order, suborder, great group, and

subgroupa

.

Order Suborder Great group Subgroup

Alfisols Boralfs Cryoboralfs Mollic Cryoboralfs

Ochreptic Cryoboralfs

Typic Cryoboralfs

Aridisols Argids Durargids Haplic Durargids

Haploxerollic Durargids

Xerollic Durargids

Haplargids Borollic Haplargids

Lithic Xerollic Haplargids

Typic Haplargids

Ustollic Haplargids

Xerollic Haplargids

Natrargids Haplic Natragids

Xerollic Natrargids

Orthids Calciorthids Xerollic Calciorthids

Camborthids Borollic Camborthid

Duric Camborthids

Lithic Camborthids

Lithic Xerollic Camborthids

Typic Camborthids

Ustollic Camborthids

Xerollic Camborthids

Durorthids Entic Durorthids

Haploxerollic Durorthids

Xerollic Durorthids

Paleorthids Xerollic Paleorthids

Entisols Fluvents Torrifluvents Ustic Torrifluvents

Xeric Torrifluvents

Xerollic Torrifluvents

Xerofluvents Typic Xerofluvents

Psamments Torripsamments Typic Torripsamments

Orthents Torriorthents Lithic Torriorthents

Typic Torriorthents (con.)
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 21

Xeric Torriorthents

Xerorthents Typic Xerorthents

Psamments Xeropsamments Typic Xeropsamment

Inceptisols Aquepts Vitrandepts Typic Vitrandepts

Mollisols Borolls Cryoborolls Argic Cryoborolls

Argic Lithic Cryoborolls

Argic Pachic Cryoborolls

Calcic Cryoborolls

Cumulic Cryoborolls

Duric Cryoborolls

Lithic Cryoborolls

Pachic Cryoborolls

Typic Cryoborolls

Rendolls Rendolls Lithic Cryic Rendolls

Xerolls Argixerolls Aridic Argixerolls

Aridic Calcic Argixerolls

Calcic Argixerolls

Calcic Pachic Argixerolls

Duric Argixerolls

Lithic Argixerolls

Pachic Argixerolls

Typic Argixerolls

Calcixerolls Aridic Calcixerolls

Typic Calcixerolls

Durixerolls Aridic Durixerolls

Orthidic Durixerolls

Haploxerolls Aridic Haploxerolls

Calcic Haploxerolls

Calcic Pachic Haploxerolls

Calciorthidic Haploxerolls

Cumulic Haploxerolls

Entic Haploxerolls

Lithic Haploxerolls

Natric Haploxerolls

Pachic Haploxerolls

Typic Haploxerolls

Natrixerolls Typic Natrixerolls

Palexerolls Aridic Palexerolls

Pachic Palexerolls

Petrocalcic Palexerolls

Typic Palexerolls

a

References used to construct this table: Acker (1992); Barker and McKell (1983); Blackburn and

others (1968, 1969b); Charley and West (1975); Daubenmire (1970); Doescher and others (1986);

Fisser (1986); Jensen (1989b, 1990); Jensen and others (1990); Lentz and Simonson (1987b); Miller

and others (1986); Passey and others (1982); Swanson and Buckhouse (1986); Swanson and others

(1986); Thorp (1931); Tueller and Eckert (1987); Weltz and others (1992).

soils of big sagebrush according to order, suborder,

great group, and subgroup. Big sagebrush has been

found growing on the following five orders: Alfisols,

Aridisols, Entisols, Inceptisols, and Mollisols. Within

these five soil orders, big sagebrush was reported as

growing on 11 soil suborders, 23 great groups, and 72

subgroups (table 1.2). Big sagebrush can be found

growing on all 12 soil textural classes—clay, silty clay,

silty clay loam, silt loam, silt, clay loam, loam, sandy

Table 1.2 (Con.)

Order Suborder Great group Subgroup

clay, sandy clay loam, sandy loam, loamy sand, and

sand—but it is most often found on a loam or sandy

loam soil (Blackburn and others 1968, 1969a;

Daubenmire 1970; Fairchild and Brotherson 1980;

Lentz and Simonson 1987a,b; Mueggler and Stewart

1980; Passey and others 1982; Shown and others 1972;

Thatcher 1959).

Chemical properties of big sagebrush soils are highly

variable among soil horizons of a given site and among
22 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 1.3—Soil chemistrya of big sagebrush soils.

Horizons OC N P K Na Ca Mg CEC CaCO3 1/3 atmos. References

A 2.8 0.25 64.0 2.5 20.8 30.5 Barker and McKell 1983b

A 1.10 .11 6.8 .5 7.2 17.6

A 2.09 .17 1.09 .30 26.9 3.96 20.5 3.40 20.4 Passey and others 1982c

B .99 .10 1.23 18.5 8.30 19.1

C .58 .07 .61 11.5 28.80 17.6

A 2.70 .25 3.52 .32 33.1 .85 32.8

B .71 .14 1.01 1.07 34.1 21.90 39.4

C .39 .37 9.05 40.0 50.70 43.2

A 1.02 .10 .88 .36 14.8 22.90 18.3

C .33 .07 .94 1.99 11.6 35.6 22.4

A 1.96 .18 2.9 .10 18.2 3.30 24.1

B .90 .10 2.0 .10 22.2 3.60 26.7

C .62 .07 .6 .30 21.8

A 1.92 .15 2.60 .10 12.1 5.10 19.6

B .31 .05 .68 1.55 16.7 27.8

C .15 .55 2.40 30.4

A 1.80 .15 2.13 .10 13.9 3.40 18.2

B .60 .07 1.20 .10 13.6 3.90 17.1

C .40 .06 .80 .20 15.7

A 1.39 .11 1.50 .20 11.5 4.35 17.7

B .65 .07 .60 .20 12.7 5.6 18.2

C .22 .50 19.0 6.83 12.2

A .62 Blank and others 1992

B .33

A 1.39 .02 Charley and West 1975

A? 2.15 .10 Doescher and others 1984

A 4.14 .19 1.25 .10 13.65 3.99 21.5 Jensen 1989a

B 2.45 1.05 .10 13.64 6.06 20.95

A&B 2.23 .64 .25 15.90 3.08 19.9 15.6 Marchand 1973

A 1.12 1.20 .20 8.40 2.80 13.0 Van Ryswyk and others 1966

B .71 1.00 .20 9.00 2.80 12.8

C .22 .70 .20 12.70 4.00 6.6

a

OC = organic carbon %; N = nitrogen %; P = phosphorus ppm; K = potassium me/100g; Na = sodium me/100g; Ca = calcium me/100g; Mg =

magnisum me/100g; CEC = cation exchange capacity me/100g; CaCO3; 1/3atmos = percent of moisture at 1/3 atmosphere. b

Values are extremes (highs and lows) for the study.

c

Values are means of horizons per site.

sites, as shown in table 1.3. For example, the percentages of organic carbon for A, B, and C horizons for a

given site were: A 2.70, B 0.71, and C 0.39. A horizon

among sites varied from 0.62 to 4.14 (table 1.3). Soil

pH of big sagebrush soils also varied among soil

horizons within a given site and among sites (table 1.4);

big sagebrush grows in soils varying in pH from 5.9 to

10.0 but is usually found growing in soil nearly neutral, that is, a pH of 7.

Annual precipitation falling on big sagebrush soils

varies from 5 to 58 inches (Barker and McKell

1983; Blackburn and others, 1968, 1969a,b;

Blackburn and Skau 1974; Blank and others 1992;

Fisser 1986; Goodrich and others 1999; Jameson

and others 1962; Mason and others 1967; Mueggler

and Stewart 1980; Passey and Hugie 1963a; Passey

and others 1982; Shown and others 1972; Tisdale and

others 1965; Van Ryswyk and others 1966). Moisture

infiltration rates of big sagebrush soils varied from

0.47 to 4.05 inches per hour (Balliette and others 1986;

Blackburn 1975; Blackburn and others 1990;

Blackburn and Skau 1974; Branson and others 1967;

Gifford 1972; Swanson and Buckhouse 1986). Balliette

and others (1986) found infiltration rates under big

sagebrush canopy to be higher than the interspaces.

Eldridge and Rosentreter (2004, p. 81) stated: “In our

study, infiltration under the shrubs was two to six

times greater than infiltration in the interspaces.”

Regardless of the taxonomical and textural classification, chemical properties, pH, annual precipitation,

or infiltration rate of big sagebrush soils, all soils

supporting big sagebrush have two characteristics in
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 23

Table 1.4—pH of big sagebrush soils.

Soil horizons

A B C Subspecies Reference State

7.1 Blackburn and others 1968 Nevada

7.4

7.7 7.5

7.5

7.3 7.5

6.9 Blackburn and others 1969a Nevada

7.6

7.0

6.6 7.2

7.0 7.4

6.9 7.0

6.6 6.6 Blackburn and others 1969b Nevada

6.7 6.8

7.0 6.7

6.4 6.6

6.3 6.4

7.2

7.7 Charley and West 1975 Utah

7.7

6.9 6.8 Mountain Cottrell and Bonham 1992 Colordao

6.8 6.5 Mountain

8.2 8.1 Basin

8.1 8.2 Basin

8.2 8.3 Wyoming

7.7 8.2 Wyoming

6.7 8.0 Basin Daubenmire 1970a Washington

6.7 7.7 Basin

6.5 7.2 Basin

6.4 7.1 Basin

6.2 7.0 Basin

6.9 8.0 Basin

6.7 6.9 Basin

6.3 6.9 Basin

7.1 7.9 Basin

6.1 7.5 Basin

6.6 7.4 Basin

6.5 6.3 Basin

6.4 7.7 Basin

7.2 7.7 Basin

6.8 7.3 Basin

6.7 7.3 Basin

6.6 7.7 Basin

6.8 7.2 Basin

7.2 7.3 Basin

6.9 7.1 Basin

6.8 7.9 Basin

6.7 7.9 Basin

6.2 7.0 Basin

6.5 6.8 Basin

6.6 7.2 Basin

7.9 7.9 Basin

6.9 7.2 Basin

6.6 7.1 Basin

7.3 7.7 Basin

5.9 6.6 Basin

6.2 7.6 Basin

6.4 6.8 Basin

6.5 6.6 6.7 Mountain Doescher and others 1984 Oregon

6.7 6.6 6.6 Mountain

(con.)
24 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

6.5 7.1 7.3 Basin

6.9 7.3 7.5 Basin

7.0 7.4 7.5 Wyoming

7.0 7.2 7.2 Wyoming

7.1 Fairchild and Brotherson 1980 Arizona

7.3

7.9 8.3 Basin Fisser 1986 Wyoming

7.8 7.9 Basin

8.1 8.5 Basin

7.1 7.4 Wyoming

7.6 7.5 Wyoming

7.5 Hazlett and Hoffman 1975 North Dakota

8.2

7.7

7.7 7.2 Wyoming Jensen 1990 Nevada

7.0 6.6 Basin

6.4 6.2 Basin

7.0 7.4 Mountain

6.2 6.3 Mountain

6.4 6.6 Mountain

7.0 7.2 Mountain

6.4 6.5 Mountain

7.1 Mountain Lentz and Simonson 1987a Oregon

7.4 Wyoming

7.3 Wyoming

6.7 Marchand 1973 California

7.6

7.5 7.6 7.8 Basin Passey and others 1982 Idaho, Utah

7.4 7.5 8.3 Basin

6.6 7.1 8.3 Basin

6.8 7.5 8.0 Basin

6.6 7.6 8.0 Basin

6.4 7.6 8.3 Basin

7.4 7.9 Basin

7.1 7.6 8.3 Wyoming

7.3 7.5 8.2 Wyoming

6.8 6.7 8.7 Wyoming

6.6 6.9 7.9 Wyoming

7.0 7.3 8.1 Wyoming

7.0 7.7 8.5 Wyoming

7.3 7.6 Wyoming

7.8 Pearson 1965 Idaho

7.8

7.8 9.1 10.0 Rickard 1964 Washington

6.0 6.5 Mountain Robertson and others 1966 Colorado

8.2 8.1 Robocker 1958 Nevada

6.9 7.3 Wyoming Van Ryswyk and others 1966 British Columbia

7.2 7.4 7.6 Wyoming

7.3 7.8 8.2

7.9 Basin Wang and others 1998 Utah

7.0 Basin-Mountain hybrid

7.7 Basin-Mountain hybrid

7.3 Basin-Mountain hybrid

6.9 Mountain

6.9 Basin

6.7 Basin-Mountain hybrid

7.0 Basin-Mountain hybrid

7.0 Basin-Mountain hybrid

Means A = 7.0; B = 7.3; C = 7.9

Range A = 5.9-8.2; B = 6.3-9.1; C = 6.6-10.0

a

Daubenmire (1970) did not recognize Wyoming big sagebrush at the time his report was published, but McArthur and

Sanderson (1999) found many of the stands to be Wyoming big sagebrush.

Table 1.4 (Con.)

Soil horizons

A B C Subspecies Reference State
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 25

common: they are well drained, and they contain low

concentrations of salts (Thatcher 1959).

Big Sagebrush Taxonomy and

Origin _________________________

McArthur (1979) notes that the word or name Artemisia was derived from an early word meaning or

referring to Mother Nature, and from Artemis who

was the Greek goddess of wild animals, the hunt,

plants, chastity, and childbirth. Nuttall (1841, p. 398)

was the first to describe and give big sagebrush its

scientific name, Artemisia tridentata. His description:

canescently tomentose; leaves cuneate, three-toothed

at the summit, upper ones entire and obtuse; flowers

paniculate; capitulum sessile, ovate and tomentose,

small; inner sepals scariose, linear-oblong. Hab. Plains

of the Oregon, and Lewis’ River. A low, but rather stout

shrub, white with a close tomentum. Leaves rather

more than an inch long, about two lines wide, more or

less deeply three-toothed, sometime entire, the upper

ones always so. Panicle much branched, the flowers

small. ( I have not seen them in a perfect state, and

therefore class this species by its apparent affinity with

the last.) Somewhat allied to A. chinensis.

Later Torrey and Gray (1843, p. 418) added to the

description of big sagebrush: “densely silvery-canescent; those of the flower-branchlets often linear and

entire; heads obovoid, spicate-glomerate, disposed in

dense compound panicles, 5-6 flowered; exterior scales

of the involucre canescent, the inner scarious.” They

also produced the first classification scheme that included big sagebrush. Later this was revised by Rydberg

(1916), then by Hall and Clements (1923), followed by

Beetle (1959, 1960), Beetle and Young (1965), Brunner

(1972), Goodrich and others (1985), McArthur (1979),

McArthur and others (1979), Ward (1960), and

Winward and Tisdale (1977). Many of these classification schemes are compared in a paper by McArthur

(1979).

The taxonomy of big sagebrush is as follows (Beetle

1959, 1960; Beetle and Young 1965; McArthur 1979,

1983; Tisdale and Hironaka 1981; Raven and others

1999):

• Kingdom: Plantae

• Phylum: Anthophyta

• Class: Eudicots

• Order: Asteraceae

• Tribe: Anthemidea

• Genus: Artemisia

• Subgenus: Tridentatae

• Species: tridentate

• Subspecies: tridentata (basin big sagebrush),

wyomingensis (Wyoming big sagebrush), vaseyana

(mountain big sagebrush).

Some authorities have divided subspecies A. t. ssp.

vaseyana into two forms or subspecies depending on

the authority being quoted. One form is called subalpine big sagebrush (Artemisia tridentata ssp.

spiciformis [McArthur and Goodrich 1986] or A. t. ssp.

vaseyana f. spiciformis [Beetle and Johnson 1982]),

which in this treatise is treated as an atypical highelevation (9,300 to 10,600 feet) mountain big sagebrush; also, Goodrich and others (1985) describe a

variety of mountain big sagebrush (A. t. ssp. vaseyana

var. pauciflora). A second form is referred to as “X” big

sagebrush by Winward and Tisdale (1977), as xeric big

sagebrush by Rosentreter and Kelsey (1991), but I

treat it as an atypical low-elevation (2,500 to 5,000

feet) mountain big sagebrush, and is described as a

subspecies of big sagebrush (A. t. ssp. xericensis) by

Hironaka and others (1983). McArthur and Sanderson

(1999) note that it is cytologically distinctive. Also,

subspecies basin big sagebrush is divided by some

authorities into forms or varieties, the typical form, f.

tridentata and f. parishii (Beetle 1959; Hall and

Clements 1923).

The dichotomous key (side bar on this page) by

McArthur and others (1979) describes the characteristics that separate the woody sagebrush from other

plants and distinguishes subspecies of big sagebrush

(bold type leads to big sagebrush).

Other workers have constructed dichotomous keys

also as an aid in identifying subspecies of big sagebrush (Beetle 1960; Beetle and Johnson 1982; Blaisdell

and others 1982; Brunner 1972; Winward 1980;

Winward and Tisdale 1977). Blaisdell and others (1982)

have compared some of these keys.

In general, mountain big sagebrush grows at higher,

cooler, and moister elevations (4,500 to 11,000 feet)

than basin or Wyoming big sagebrush; basin big sagebrush grows lower at warmer and dryer elevations

(2,500 to 7,000 feet) than mountain big sagebrush; and

Wyoming big sagebrush is found at the hottest and

driest elevations (2,500 to 7,000 feet) of the big sagebrush subspecies (Beetle and Johnson 1982; Bonham

and others 1991; Frisina and Wambolt 2004;

Hodgkinson 1989; Johnson 1987; McArthur 1979;

Mahalovich and McArthur 2004; McDonough and

Harniss 1975; Winward 1983; Winward and Tisdale

1977). Monsen and McArthur (1985) and Goodrich

and others (1999) reported average annual precipitation for mountain big sagebrush stands to be about 17

inches, 14 inches for basin big sagebrush, and 11

inches for Wyoming big sagebrush. Tisdale and

Hironaka (1981) noted that stands dominated by

Wyoming big sagebrush were the first to became water

deficient (mid-July), basin big sagebrush stands were

second (late July to early August), and mountain big

sagebrush stands were the last to become water deficient (September). Barker and McKell (1983), studying the habitat characteristics of contiguous populations of basin and Wyoming big sagebrush, found that
26 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

1a. Head with both ray and disc flowers; pappus of several to many scales.

1b. Heads with only disc flowers or if ray flowers present then pappus of capillary bristles or lacking.

3a. Pappus of capillary bristles, at least in part.

3b. Pappus lacking...Artemisia (sagebrush).

26a. Heads with both ray (marginal) flowers and disc flowers; plants subshrubs or shrubs.

26b. Heads with disc flowers only; plants shrubs.

30a. Plants up to 5 dm high.

30b. Plants usually over 5 dm high (42b provide most exceptions to 5 dm height).

36a. Leaves silvery-canescent, linear to linear-oblanceolate, mostly entire (occasionally with a few irregular

teeth), or leaves deeply divided into three of more linear or linear-oblanceolate lobes.

36b. Leaves not silvery-canescent, narrowly lanceolate to broadly cuneate or fan-shaped, typically 3-

tooth or lobed (upper leaves may be entire).

40a. Plants low-growing, flat-topped shrubs up to 8 dm high; leaves somewhat viscid; heads occurring

singly or occasionally up to three arranged in short interrupted spike or raceme like

inflorescences; heads large with up to 20 disc flowers each; occurs in high mountainous areas of

central Colorado, western Wyoming, Utah, central Sierras of California, and Carson Range of

Nevada.

40b. Plants ranging from dwarf to tall, arborescent forms up to 4.5 m; leaves not viscid;

inflorescences of numerous heads arranged into leafy panicles; heads smaller with three

to eight disc flowers; most widespread and common shrub of Western North America.

Artemisia tridentata (big sagebrush).

41a. Plants uneven-topped shrubs with flowering stalks arising throughout the crown;

leaves narrowly lanceolate to cuneate; odor of crushed leaves pungent

42a. Mature plants often arborescent (with single trunk-like main stem), usually from

1 to 2 m but in some forms up to 4.5 m high; leaves narrowly lanceolate with

margins not curving outward; average persistent 5.6 times its width; blooming

starts in late August or September; odor strongly pungent; normally occurs

below 2,100 m in dry, deep, well-drained soils on plains, valleys, and foothills. A.

tridentata ssp. tridentata (basin big sagebrush).

42b. Mature plants with several main branches usually less than 1 m high; leaves

narrowly cuneate to cuneate with margins curved outward; average persistent

leaf length is 3.1 time its width; blooming starts in late July or August, odor

pungent; occurs on dry, shallow, gravelly soil from 1,500 to 2,100 m. A.

tridentata ssp. wyomingensis (Wyoming big sagebrush).

41b. Plants usually even-topped shrubs with flower stalks arising from the upper crown

portions; leaves broadly cuneate to spatulate; average persistent leaf length is 4.0

time its width; blooming may begin in July; odor slightly pungent to pleasantly mintlike; occurs from 1,400 to 3,000 m in deep, well-drained soils...A. tridentata ssp.

vaseyana (mountain big sagebrush).

basin big sagebrush grew in wetter and more fertile

habitats, having a deeper soil than Wyoming big

sagebrush. In addition, the vegetative tissue of basin

big sagebrush contained great amounts of nitrogen,

magnesium, phosphorus, potassium, iron, and zinc.

Soil water content at 1/3 atmosphere was higher for

sites supporting basin big sagebrush.

Shumar and Anderson (1986) found that basin and

Wyoming big sagebrush distributions were closely

associated with soil texture. Basin big sagebrush was

supported by sandy soils and Wyoming big sagebrush

by silty textured soils. Barker and McKell (1983)

found in northeastern Utah and southwestern Wyoming that Wyoming big sagebrush grew mainly on

Aridisols and basin big sagebrush on Entisols. Swanson

and others (1986) found in eastern Oregon that Wyoming big sagebrush often grew on Aridisols soils,

mountain big sagebrush on Mollisols at higher elevations, and basin big sagebrush on deeper soils of either

order of soils. Jensen (1989a, 1990) noted that all three

subspecies of big sagebrush grew on Mollisols soils of

northeast Nevada. Cottrell and Bonham (1992), in a
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 27

study conducted in the Piceance Basin of Colorado,

noted big sagebrush subspecies distribution was related to soil moisture, temperature, soil depth, and

parent material. Here, basin big sagebrush tends to

occupy deep, sandy soils, whereas mountain big sagebrush occurred at cool, moist, higher elevations, and

Wyoming big sagebrush tends to be on shallow, silty

soils where moisture stress is greater.

Because of the moisture gradient among the three

subspecies of big sagebrush, understory or associated

plant species differ among subspecies with Wyoming

big sagebrush representing the dry side (xeric), mountain big sagebrush the wet side (mesic), and basin big

sagebrush in between. Winward (1983) pointed out

that fewer perennial forbs grow in association with

Wyoming big sagebrush than with the other two subspecies. Grasses associated with Wyoming big sagebrush include bluebunch wheatgrass (Agropyron

spicatum), needle-and-thread (Stipa comata),

squirreltail (Sitanion hystrix), and Salina wildrye

(Elymus salina). Winward (1983, p.16) stated, “Some

Wyoming big sagebrush sites may have about 25

percent bare ground even under natural conditions.”

On mountain big sagebrush sites, many species of

forbs, grasses, and nonsagebrush shrubs are present

(Winward 1983). Winward (1983, p.16) described the

associated vegetation of mountain big sagebrush: “It is

not uncommon to find 40 plant species associated with

this sagebrush.” Grasses associated with mountain

big sagebrush include bluebunch wheatgrass, Idaho

fescue (Festuca idahoensis), needle-and-thread,

junegrass (Koeleria cristata), mountain brome (Bromus

carinatus), basin wildrye (Elymus cinereus), and slender wheatgrass (Agropyron trachycaulum) (Winward

1983). At higher elevations, dense stands of mountain

big sagebrush (subalpine big sagebrush) often support

gophers (Thomomys ssp.) (Winward 1983). As stated

earlier, basin big sagebrush sites are in between the

dryness of Wyoming and the wetness of mountain big

sagebrush. Forbs are more prevalent than in Wyoming big sagebrush, and grasses of Wyoming big

sagebrush are also present in basin big sagebrush

along with basin wildrye (Winward 1983).

Chromatographic (both paper and thin-layer) analysis of ethanol extractions of big sagebrush leaf samples

led to the development of a simple field technique that

can be used as an aid in identifying or separating

subspecies of big sagebrush (Hanks and others 1973;

Holbo and Mozingo 1965; Young 1965a,b; Young and

Asplund 1963, 1964). After chromatographic development, compounds were localized by exposing the wet

chromatogram in a dark environment to long wave

ultraviolet light (3,660 angstroms), which revealed

the color and position of the various diagnostic spots.

Taylor and others (1964) exposed moist seeds of mountain and basin big sagebrush to ultraviolet light and

observed that mountain big sagebrush seed fluoresced

and basin big sagebrush seeds did not. Young (1965a)

found that exposing the extracting bottle (2 grams of

vegetative leaf tissues to 10 ml ethanol) and noting the

color of the fluorescent would give a preliminary classification of big sagebrush subspecies. Mountain big

sagebrush extraction bottles contained a light blue

fluorescent, and basin big sagebrush red. Wyoming

big sagebrush was undescribed at that time (Beetle

and Young 1965). Refinements were made to the

technique and applied to dried leaves from the field or

from herbarium specimens (Winward and Tisdale

1969). Later, Stevens and McArthur (1974) substituted water for ethanol and were able to separate all

three subspecies as follows: mountain was intense

blue, Wyoming was light blue, and basin was pale blue

to colorless. Since then, this technique has been applied to spectrophotometry of both alcohol and water

extractions as a means of identifying subspecies of big

sagebrush and putative hybrids among subspecies

(McArthur and others 1988; Shumar and others 1982;

Spomer and Henderson 1988). Kelsey and others (1976)

discuss the usefulness of sesquiterpene lactones and

thin-layer chromatography as an aid in identifying

subspecies of big sagebrush.

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Explanation of Plate I (Diettert 1938) __________________________________

Figure 1—Young flower head. X13. Section of a head at this stage of development is shown in Fig.6.

Figure 2—Older head, just prior to opening. X13.

Figure 3—Portion of flowering branch, showing the arrangement of heads. X11/2.

Figure 4—Section of tip of young flowering branch, showing beginning of heads. X50.

Figure 5—Section of young flowering bud, showing initiation of flowers. X50.

Figure 6-10—Early stages in the development of flowers. X50.

Figure 11—Section of young flower, showing relation of parts at megaspore mother cell stage. X50.

Figure 12—Section of flower just prior to anthesis. X16.

Figure 13—Section of a portion of two corolla lobes, showing interlocking of marginal cells. X245.

Figure 14—A single flower just after anthesis. X15.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 37

Explanation of Plate V (Diettert 1938) _________________________________

Figure 60—Embryo sac with 2-celled embryo and 2-celled endosperm. X165.

Figure 61—Embryo sac with a 2-celled embryo and an undivided primary endosperm cell. X165.

Figure 62-71—Successive stages in the development of the embryo. X165.

Figure 72-73—Embryo sacs with young embryos and endosperm. Note enlargement of chalazal antipodal cell in Fig. 73. X165.

Figure 74—Embryo sac with embryo and endosperm. Note the persisting antipodals. X50.

Figure 75—Nearly mature seed. Endosperm shown by dotted region. X35.
38 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Explanation of Plate VI (Diettert 1938)_________________________________

Figure 76-79—Longitudinal sections of foliar primordia. X245.

Figure 76—Section through stem tip, showing initiation of leaf primordium by periclinal divisions of the second and third layers of

the tunica (T2 and T3).

Figure 77—Primordium emerging as a papillate protuberance.

Figure 78—Primordium about 80 microns high. Note beginning of trichome on abaxial side.

Figure 79—Primordium 175 microns long. Note development trichomes on abaxial side.

Figure 80-86—Transverse sections of foliar primordia. Drawings showing cellular arrangement (a) x245; outline drawings (b) x50;

shaded area in outline drawings indicates region of the midrib.

Figure 80—Primordium 50-60 microns high, 30 microns from base.

Figure 81—Primordium 75-100 microns high, 40 microns from base.

Figure 82—Primordium 120 microns high, 40 microns from base.

Figure 83—Primordium 170 microns high, 60 microns from base.

Figure 84—Primordium 275 microns long, 60 microns from base.

Figure 85—Primordium 360 microns long, 200 microns from base. Note development of trichomes.

Figure 86—Primordium 475 microns long, 120 microns from base.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 39

Explanation of Plate VII (Diettert 1938) ________________________________

Figure 87-90—Transverse sections of young leaves: (a) portion of leaf showing cellular arrangement. Nuclei shown in outline only

in cells of palisade layers. X245. (b) outline of entire leaf from which (a) was taken. Shaded areas indicate the veins. Portion to right

of broken line shown in (a). X50.

Figure 87—Young leaf 1000-1200 microns long, 300 microns from base. Note beginning of the two major lateral veins. Trichomes

on adaxial side just beginning to develop; trichomes on a abaxial side not shown.

Figure 88—Young leaf 1.5 mm. long, about .8 mm. from base.

Figure 89—Young leaf 3-5 mm. long. Note marginal meristem (M.M.)

Figure 90—Young leaf 1.5-2 cm. long, about 7 mm. from base. Note mature vessels in

largest vein. (b) E. + P. includes the epidermal and palisade layers; S. M., the spongy

mesophyll and veins.
40 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Explanation of Plate VIII (Diettert 1938) _______________________________

Figure 91—(a) Transverse section of portion of leaf, approximately 2.5 cm. long, 1.2 cm. above base and about 3 mm. below

forking of midrib. Shortly after the cessation of cell division and the beginning of cell enlargement. X245. (b) Outline of entire section

of leaf at the same level. Portion to right of broken line shown in (a). E. + P., epidermal and palisade layers; S. M. spongy mesophyll

and veins. Veins indicated by shaded area. X50.

Figure 92—Transverse section of portion of mature leaf. U.E., upper epidermis; U.P., upper palisade; S.M., spongy mesophyll and

veins; L.P., lower palisade, L.E., lower epidermis. Note the fibers (shaded) associated with vessels. X245.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 41

Explanation of Plate IX (Diettert 1938)_________________________________

Figure 93—Longitudinal section of portion of mature leaf. Legend same as in Fig. 92. Note that the spongy mesophyll is aerated

from both side through the palisade layers. X165.

Figure 94—Paradermal section through the spongy mesophyll zone. Note the small spaces in this region. X165.

Figure 95—Paradermal section through the palisade layer. X165.

Figure 96—Portion of epidermal layer. X165.

Figure 97—Vascular system of portion of a leaf just below the lobes. Reconstructed from a series of paradermal sections. A, marginal

vein; B, major vein leading into a marginal lobe; C, major vein leading into the central lobe. X11.

Figure 98—Mature leaves, showing variations in size and form and the major veins. X1/3.
42 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Explanation of Plate X (Diettert 1938) _________________________________

Figure 99—Mature glandular trichome. X365.

Figure 100-105—Successive stages in development of the glandular trichomes. X365.

Figure 106-107—Glandular trichomes as seen in transverse section of the leaf, corresponding to Figs. 104 and 99, respectively.

X365.

Figure 108—Two cells of a mature glandular trichome as seen in paradermal section of the leaf. X365.

Figure 109—Mature cover trichome showing entire half of apical cell. X165.

Figure 110—Portion of a mature cover trichome. X365

Figure 111-119—Successive stages in development of the cover trichomes. X365.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 43

Explanation of Plate XVI (Diettert 1938) _______________________________

Figure 145—Transverse sections of older stems. Note the eccentricity; a, b, c—caused by death of flowing branches; d, e, f–caused

by the death of cambium. Natural size.

Figure 146, 147—Portions of transverse sections of older stems. Note layers of interxylary cork between the annual wood rings. Fig.

146, X10; Fig. 147, X12.
44 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Explanation of Plate XVIII (Diettert 1938) ______________________________

Figure 152, 153—Transverse sections of early and late wood, respectively. X180.

Figure 154—Radial section of an older stem. Note the interxylary cork layer between the two wood rings. X45.

Figure 155—Tangential section of a stem, showing portions of the two latest wood rings. Note the interxylary cork (c)

between the two rings; also the progressive suberization of the rays in the latest ring. X27.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 45

Figure 160—Transverse section of stem, collected September 29, 1935. Ph.–phloem; Ca–cambium; Xy.–xylem; X365.

Figure 161—Transverse section of stem, collected April 13, 1936. New wood ring about 65 microns wide at this stage. Ph.–phloem;

Ca.–cambium; Xy.–xylem; Int. C. Ca.–interxylary cork cambium. X365.

Figure 162—Transverse section of stem, collected May 12, 1936. New wood ring about 330 microns wide at this stage. Only a portion

of the new ring is shown in the drawing. X365.

Figure 163—Transverse section of stem, collected August 1, 1936. Xy.–xylem; Int. Cork–interxylary cork. X365.

Explanation of Plate XX (Diettert 1938) ________________________________
46 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 47

Chapter

II

Birds, Mammals, and

Reptiles Associated

With Big Sagebrush

This chapter deals with birds, mammals, and reptiles associated with the three main

subspecies of big sagebrush: basin big sagebrush (Artemisia tridentata ssp. tridentata);

Wyoming big sagebrush (A. t. ssp. wyomingensis) and mountain big sagebrush (A. t. ssp.

vaseyana). (Fungi, insects, mites, spiders, scorpions, lichens, and so forth are discussed

in chapter III.) Birds, mammals, and reptiles associations vary from obligate to

facultative. “Obligate associations” are those associations necessary for the animal to

complete its life cycle. “Facultative associations” are those associations that vary from

being largely dependent on big sagebrush, say for 80 percent of the time, to infrequent

use of big sagebrush, perhaps 20 percent of the time.

Birds ____________________________________________________________

A number of bird species have an obligate relationship with big sagebrush. These

include sage grouse (Centrocercus urophasianus), sage thrasher (Oreoscoptes montanus),

sage sparrow (Amphispiza belli), Brewer’s sparrow (Spizella breweri), and perhaps the

green-tailed towhee (Pipilo chlorurus), and they will be discussed below (Braun and

others 1976; McEwen and DeWeese 1987). Studying the number of birds and bird

species along a Great Basin elevational gradient near and in the Great Basin National

Park of east-central Nevada, Medin and others (2000) observed: “Both total number of

individual birds and bird species appeared to reach highest values in study plots with

a substantial component of mountain big sagebrush.”

Obligate Bird Species

Sage Grouse—Sage grouse populations have reached a historical low throughout

their entire range (Autenrieth 1986; Beck and others 2003; Connelly and Braun 1997).

Malmsbury (1996) and Braun (1995) reported that sage grouse were once present in

as many as 27 counties in Colorado, but are now common in only five to seven. In Oregon,

Crawford and Lutz (1985) estimated that sage grouse habitat has decreased by nearly

50 percent and that the abundance of sage grouse within the existing range has declined

by about 60 percent. There is concern that sage grouse could be extirpated from the

State.
48 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Sage grouse populations are similarly affected in

Idaho. The Magic Valley Region of south-central Idaho

at one time had 279 active strutting grounds; now only

50 are active—a reduction of 82 percent (Mattise

1995). This region is typical of the entire State. Idaho

is one of several States which form the core of sage

grouse habitat in the United States. Biologists from

Wyoming and Montana are reporting declines in sage

grouse populations as well (Connelly and Braun 1997;

Western States Sage Grouse Technical Committee

1995).

Utah sage grouse populations are declining in 19

counties, stable in two, and increasing in one (Beck

and others 2003; Western States Sage Grouse Technical Committee 1995). Sage grouse occupy only 50

percent of their former range. Today populations are

about half or less of those in the mid-1800s, and for

some populations only 10 percent of late 1930s populations (Welch and others 1990).

A petition was submitted to the United States Fish

and Wildlife Service in May 1999 to list sage grouse as

endangered in the State of Washington (Connelly

1999).

Sage grouse—spiny-tailed pheasant—often known

locally as sage hen or sage chicken, is the largest

grouse native to North America. This species was

discovered by 19th century explorers Lewis and Clark

above the headwaters of the Missouri River and on the

plains of the Columbia River. They named it the “cock

of the plains” (Rasmussen and Griner 1938). Sage

grouse are gallinaceous birds, meaning they possess

specialized stomach or gizzard. However, their gizzard is thin walled and unsuited for digesting seeds

(Autenrieth 1986). Sage grouse are a mottled, brownish-gray in color (fig. 2.1) with slight sexual differences

during the nonbreeding periods. However, mature

Figure 2.1—A sage grouse hen watching over her

brood (photo by Bruce L. Welch).

males average about 6 pounds but can weigh as much

as 7 pounds (Girard 1937; Patterson 1952; Roberson

1986). Females weigh about half as much as males.

No other North American game bird is as inextricably dependent upon one plant species as sage grouse is

on big sagebrush (Artemisia tridentata Nutt.) and its

near relatives (Peterson 1995; Roberson 1986). They

have an obligate relationship with big sagebrush.

Rasmussen and Griner (1938) observed close agreement between the original range of sage grouse and

the distribution of big sagebrush; also compare Beetle’s

(1960) distribution map of big sagebrush with

Patterson’s (1952) sage grouse range map. Patterson

(1952) observed that the birds showed no signs of

adjusting to the eradication of big sagebrush; also see

Braun and others (1977), Dalke and others (1963), and

Roberson (1986). Sage grouse use big sagebrush for

food and numerous cover requirements including escaping, roosting, loafing, brooding, and nesting (Girard

1937). They are seldom found far from these plants

(Peterson 1971).

The dependence of sage grouse on big sagebrush is

illustrated by the food preferences of the bird. From

October to April, big sagebrush leaves and short shoots

make up from 90 to 100 percent of the sage grouse diet

(Braun and others 1977; Grinnell and others 1930;

Patterson 1952; Roberson 1986; Rogers 1964; Wallestad

1975a; Wallestad and others 1975). Thus, during 7

months, or 58 percent of the year, sage grouse eat

nearly pure diets of big sagebrush.

During spring and summer when other foods are

available, adult sage grouse still consume large quantities of big sagebrush. Patterson (1952) reported, in a

Wyoming study, that it was only during the summer

that big sagebrush made up less than 80 percent of the

sage grouse diet. He found that big sagebrush comprised 87 percent of the spring diet and 45 percent of

the summer diet of adult sage grouse. Rasmussen and

Griner (1938) found that big sagebrush comprised 88

percent of the spring diet and 49 percent of the summer diet of adult sage grouse in the Strawberry Valley

of Utah. In Montana, Martin (1970) reported that big

sagebrush made up 34 percent of the summer diet of

adult sage grouse. Also in Montana, Wallestad and

others (1975) indicated that big sagebrush comprised

84 percent of the spring diet and 8 percent of the

summer diet of adult sage grouse. In Idaho, Gates and

Eng (1983) found that big sagebrush comprised 77

percent of the spring/summer diet of adult sage grouse.

Leach and Hensley (1954) and Leach and Browing

(1958) found that the late summer diet of California

sage grouse was 42 percent big sagebrush. Rogers

(1964) reported that big sagebrush comprised 60 to

100 percent of the spring diet and 12 to 70 percent of

the summer diet of Colorado sage grouse.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 49

Diet of juvenile sage grouse differs from that of

adults (Drut and others 1994; Klebenow and Gray

1968; Peterson 1970; Rasmussen and Griner 1938).

Sage grouse do not start life eating large quantities of

big sagebrush but do eat large amounts of forbs and

insects during the first 3 or 4 months of life at a season

when those sources are at peak availability. Rasmussen

and Griner (1938) compared the diet of adult and

juvenile sage grouse over the course of a 3-year study.

They found that the juvenile diet in June was still a

significant 25 percent big sagebrush, along with 27

percent forbs and 48 percent insects, while the adult

diet consisted of 95 percent big sagebrush, 4 percent

forbs, and 1 percent insects. The consumption of insects on the part of adults never exceeded 5 percent

even though insects were obviously present for the

juveniles to eat. In August, adult diets contained high

amounts of goldenrod at 57 percent and just 1 percent

for juveniles, while their consumption of big sagebrush was 30 percent and 36 percent, respectively.

Obviously, the adults and juveniles during June, July,

and probably August were utilizing different food

resources. At 3 to 4 months of age the juvenile diet

becomes similar to the adult diet (Drut and others

1994; Klebenow and Gray 1968; Peterson 1970;

Rasmussen and Griner 1938).

During the growing season, forbs can boost nutritive

levels in the diet of adult sage grouse. Barnett and

Crawford (1994) in an Oregon study reported that

forbs during the March 4 to April 8 period contained

higher amounts of crude protein, calcium, and phosphorus than did big sagebrush. They suggested that

consumption of these forbs could improve the nutritional status of the hens prior to laying and should, by

inference, increase reproductive success. From their

dietary studies, big sagebrush accounted for 52.4 percent of the dry matter intake while forbs made up 47.4

percent. Thus, forbs should be encouraged whenever

possible but not at the expense of big sagebrush; forbs

offer little to zero cover. Forb production is more

precipitation sensitive than big sagebrush, and in

some years the forb production could be nil. Some

years, snow cover or cold weather could delay growth

or emergence of forbs, which could make them not

available soon enough to have any nutritional benefit

for egg-laying hens.

Sage grouse have preferences for certain subspecies

of big sagebrush. Welch and others (1991) conducted a

study to determine sage grouse preference for three

subspecies and nine accessions of big sagebrush. The

subspecies were mountain big sagebrush, Wyoming

big sagebrush, and basin big sagebrush. Results of the

Welch and others (1991) study, by order of preference,

were mountain big sagebrush, Wyoming big sagebrush, and basin big sagebrush (see fig. 2.2). They

observed differential preferences for accessions within

a subspecies (fig. 2.3). Despite the preference displayed by sage grouse, the significance to their well

being is questionable through a preference ranking

alone. Welch and others (1991) noted that when the

forage of a preferred subspecies or accession was

exhausted, the birds readily ate less preferred subspecies or accessions that generally met or exceeded the

nutritional value of the preferred taxa. However,

Remington and Braun (1985) provided evidence that

Wyoming big sagebrush was preferred over mountain

big sagebrush and alkali sagebrush (A. longiloba), but

their study is not definitive because the sagebrushes

grew in different environments.

Figure 2.2—The percentage of total sage

grouse bites per subspecies of big sagebrush

per day of trial. The 3 subspecies of big

sagebrush are mountain, basin, and Wyoming (after Welch and others 1991).

Figure 2.3—The percentage of total sage grouse bites

per accession within the mountain big sagebrush group

per day (after Welch and others 1991).
50 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Sage grouse eat a variety of sagebrush taxa, but to a

lesser extent than big sagebrush. These other sagebrush taxa are alkali sagebrush (A. longiloba), black

sagebrush (A. nova), low sagebrush (A. arbuscula),

and a half-shrub fringed sagebrush (A. frigida) (Barnett

and Crawford 1994; Patterson 1952; Rasmussen and

Griner 1938; Remington and Braun 1985; Rogers

1964; Wallestad and others 1975).

The importance of big sagebrush in the life history of

sage grouse is further illustrated in the bird’s preference for cover and the selection of nesting sites

(Autenrieth 1986; Braun and others 1977; Connelly

and others 1991; Hulet and others 1986; Patterson

1952; Rasmussen and Griner 1938; Roberson 1986;

Wallestad 1975a; Wallestad and Pyrah 1974). Sage

grouse hens usually nest under big sagebrush plants.

Patterson (1952) found in Wyoming that 92 percent of

300 nests were under big sagebrush. Similar results

were found in Montana (Wallestad and Pyrah 1974)

and Idaho (Klebenow 1969) where 100 percent of the

nests were located under big sagebrush plants.

Rasmussen and Griner (1938) in Utah reported that

66 percent of the nests were located under big sagebrush and 33 percent under silver sagebrush (A. cana).

Hulet and others (1986) found on the U.S. Sheep

Experiment Station, near Dubois, ID, that 52 percent

of 30 nests were under big sagebrush, 17 percent

under antelope bitterbrush (Purshia tridentata), 14

percent under tall three-tip sagebrush (Artemisia

tripartita), 10 percent under dead sagebrush, and 7

percent under Russian thistle (Salsola iberica). Nest

predation for the Hulet and others (1986) study at 37

percent was higher than that reported for the

Rasmussen and Griner (1938) study at 26 percent and

higher still than the reported nesting failure of 24

percent due to all causes in the Wallestad and Pyrah

(1974) study. Connelly and others (1991) in the same

region of Idaho found that 79 percent of 84 nests were

under big sagebrush plants and that nesting success

was higher for nests under big sagebrush (53 percent)

than for nests under non-big sagebrush plants (22

percent). The non-big sagebrush plants were rabbitbrush (Chrysothamnus spp.), snowberry

(Symphoricarpos oreophilus), and antelope bitterbrush.

Hens select nesting sites beneath big sagebrush

plants that have a relatively large canopy cover and

are relatively tall (Braun and others 1977; Roberson

1986). Autenrieth (1986) observed that big sagebrush

plants with an umbrella effect were usually selected

by the hen. He attributed this selection to improved

survival of the hen and improved nest success due to

protective camouflaging. Autenrieth (1986, p. 766)

concluded: “The importance of big sagebrush cover for

nesting cannot be overestimated.” Because sage grouse

hens show strong fidelity for specific nesting areas,

these areas need to be identified and conserved (Fisher

and others 1993).

Most studies indicate that the majority of nests are

under the tallest plants and in the densest canopy

cover. In a Utah study, Rasmussen and Griner (1938)

reported that areas with less than 15 percent big

sagebrush cover and less than 18 inches (45 cm) tall

were rarely chosen for nesting and gave a low nesting

success. They noted (p. 862) “an exceptional dense

growth of mature sage (50 percent cover and 18 or

more inches tall) had revegetated the area and provided a very desirable nesting cover as indicated by the

fact that nesting success was highest in this type

during both years.” Patterson (1952) reported similar

results in a Wyoming study. Hulet and others (1986)

found in an Idaho study that the canopy cover of big

sagebrush 11 feet2 surrounding nests was 49 percent

versus 17 percent 100 feet2 surrounding the nests; or

in other words, the hens were choosing small denser

stands of big sagebrush within an 100 feet2 area in

which to build their nests. Big sagebrush plant height

for 11 feet2 surrounding nests was 18 inches versus 9

inches for 100 feet2 (9.3 m2) surrounding nests. Again,

with plant height held constant, a Montana study by

Wallestad and Pyrah (1974) found that successful

nests were in stands having a higher big sagebrush

canopy cover (27 percent) than unsuccessful nests (20

percent). In Oregon, Gregg and others (1994) reported

similar results. They found that shrub canopy cover

(Wyoming big sagebrush comprised 87 percent of the

shrub cover) at nonpredaceous nests was greater at 41

percent than for predaceous nests where the shrub

cover was 29 percent. Gregg and others (1994) also

found that the cover of grass was greater at the

nonpredaceous nest sites, an observation also made by

others (Autenrieth 1986; Beck and Mitchell 2000;

Rasmussen and Griner 1938; Roberson 1986). For

Washington, Sveum and other (1998) found that nesting sites contained Wyoming big sagebrush canopy

cover values of 51 and 59 percent versus 6 and 7

percent Wyoming big sagebrush canopy cover for random sites. Canopy cover of Wyoming big sagebrush

for nesting area was 20 and 18 percent compared to

random sites of 7 and 7 percent. Bunnell and others

(2004) reported that Strawberry Valley (central Utah)

sage grouse hens nested in mountain big sagebrush

stands having a canopy cover of 25 percent.

These 12 reports conducted in seven Western States

indicate the following about nesting habitats of sage

grouse. First, sage grouse hens selected big sagebrush

plants over other species of wildland plants including

other species of shrubs. Secondarily, the preferred

canopy cover ranges between 20 and less than 50

percent, and sage grouse prefer plants that are at least

18 inches in height with a good understory of grasses

and forbs. More importantly, nest success was greatest at sites with these characteristics. Nesting densities varied from one nest per 7 to 15 acres (Patterson

1950; Patterson 1952; Rasmussen and Griner 1938).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 51

Basically the “Guidelines for Maintenance of Sage

Grouse Habitats” of Braun and others (1977) remains

valid for nesting habitat.

Connelly and others (2000) in their guidelines placed

big sagebrush canopy cover for nesting habitat at 15 to

25 percent. Why the lower minium value of 15 percent

is not clear. The vast majority of studies cited by them

reported much higher canopy cover values. Autenrieth

(1986, p.765) found: “Big-sage canopy per tenth acre

surrounding the nest bush ranged from 23.4 to 38.1

percent for five study areas.” Connelly and others

(2000) values perhaps better represent minimum than

maximum cover values. They do describe minimum

cover values for grasses (15 percent or more and

minimum height of 7 inches) and for forbs (10 percent

or more and minimum height of 7 inches). What are

not clear are what portion of the grass cover should be

under or adjacent to big sagebrush plants and what

portion in the interspaces among the big sagebrush

plants. Two statements within the Connelly and others (2000) report seem to be in conflict. These are (p.

970): “However, grouse nesting under sagebrush experience greater nest success (53%) than those nesting

under other plant species (22%) ”; and (p. 971 ): “Grass

height at nests under non-sagebrush plants was greater

(p<0.01) than that associated with nests under sagebrush, further suggesting that grass height is an

important component for nesting sage grouse.” Value

of grass in the nesting habitat of sage grouse was

expressed by Rasmussen and Griner (1938, p. 864):

“The presence of grasses and weeds interspersed with

the sagebrush made a more successful nesting type

than sage of equal density without the understory.”

But these needs of nesting habitat are often at

conflict with grazing interests. For example, Baxter

(1996, p. 60) in his article “Improving rangeland health

by thinning dense sagebrush stands with tebuthiuron

(Spike 20P),” states: “when big sagebrush cover reaches

12 to 15 percent, the understory production of other

plants decreases as canopy cover increases” (also see

Phillips 1972). Their recommendation would thin big

sagebrush stands before enough canopy cover developed to support preferred sage grouse nesting habitat.

Needs of sage grouse broods differ from that of

nesting habitat, although big sagebrush remains an

important component. It is the food requirement of the

chicks that is the driving force behind the search for

brooding habitat. Insects and forbs are important in

the diet of chicks during the first 12 weeks or so of life,

after which their diet is almost the same as adults

(Drut and others 1994; Fisher and others 1996;

Patterson 1952; Peterson 1970; Pyle and Crawford

1996; Rasmussen and Griner 1938).

Martin (1970) found in a 3-year study conducted in

Montana that big sagebrush canopy cover for brooding

habitat was 19 percent (18 percent for a study conducted in Idaho; Musil and others 1994). However,

Martin (1970) noted that young broods (less than 6

weeks old) selected habitats with a big sagebrush

canopy cover of 14 percent. He observed that by August and September broods and brood groups were

located on areas comparable to summering adults,

having a big sagebrush canopy cover of about 25

percent. This 25 percent big sagebrush canopy cover

for summering adult sage grouse was also recorded by

Gregg and others (1993) in Oregon. Similar results

were reported from another Montana study conducted

by Wallestad (1971). He found broods occupying big

sagebrush habitats that had canopy cover of 14 percent for June, 12 percent for July, 10 percent for

August, and 21 percent for September. Dunn and

Braun (1986) in Colorado found broods occupying big

sagebrush habitats that had a mean canopy cover of 24

percent from July to September. In another Montana

study, Peterson (1970) noted that the canopy cover of

big sagebrush varied in brooding habitat from 1 to 20

percent. Wallestad (1975a) found that 90 percent of

broods studied in central Montana were in areas

where big sagebrush canopy cover varied from 0 to 25

percent. In both of these Montana studies, feeding

sites with low cover were never far from higher density

big sagebrush escape areas. Wallestad (1975a, p. 33)

observed:

During the summer less than 15 percent of the observations occurred in dense (25 percent and greater canopy

coverage) sagebrush until October, when 40 percent of

the birds were observed using sagebrush of this density. During August and September, approximately 65

percent of all grouse observations were recorded in

bottomland types (alfalfa fields and greasewood bottoms). ...The time of shift from ranges dominated by

sagebrush to bottomland types was dictated by the

condition of vegetation as influenced by moisture conditions in any given year. The first killing frost of the

season usually occurred any time after September 1.

With the frost, many forbs were destroyed, forcing sage

grouse to turn to sagebrush for food. Jorgensen (personal communication 1973) reported moisture content

of sagebrush leaves increased with fall rains. The

increased moisture content may make sagebrush more

palatable than during summer. Many years the shift

occurred just prior to the hunting season, baffling

hunters who consistently hunted alfalfa fields.

From the available research, the ideal brooding

habitat would consist of big sagebrush with a canopy

cover of some 25 percent with a small creek running

through it. The riparian zone about 50 feet wide would

reduce the big sagebrush canopy cover to 0 and provide

the needed forbs for the chicks to eat with the adjacent

big sagebrush cover providing shading, loafing, escape, food, and a source of insects. This situation

would be similar to a strip spraying project described

by Autenrieth (1969). During the wet years of the

study, broods used sprayed strips more than leave

strips, but during dry years leave strips were used

more than the sprayed. Ranchers in Idaho also noted

changes in brood movements between wet and dry

years—during wet years they saw fewer broods in
52 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

their fields that reflected good forb production in the

big sagebrush stands (Autenrieth 1986).

Brooding habitat, as important as it is, occupies only

a small percentage (perhaps 20 percent) of the total

habitat needs of sage grouse. Connelly and others

(2000) suggest 40 percent. Therefore, claims that large

big sagebrush control projects are going to improve

brooding habitat must be subject to careful examination to see if the desire is to help sage grouse or improve

grass availability (Fisher and others 1996). Following

and citing the guidelines published by Braun and

others (1977) and the recommendations of Autenrieth

(1986) will avoid the outdated but often used concept

that sage grouse habitats will be improved by killing

big sagebrush, when the facts clearly show just the

opposite results (Peterson 1995).

Summering, broodless hens and males select big

sagebrush stands with canopy cover ranging from 20

to 35 percent and some as high as 50 percent (Autenrieth

1986; Braun and others 1977; Ellis and others 1989;

Martin 1970; Patterson 1952; Roberson 1986;

Wallestad 1975a; Wallestad and Schladweiler 1974;

Welch’s personal observations; see chapter I). Connelly

and others (2000, p. 980) in their guidelines, however,

note: “Generally, 10-20% canopy cover of sagebrush

and < 25% total shrub cover will provide adequate

habitat for sage grouse during summer.” Based on the

values cited in other studies and personal observations, their big sagebrush canopy cover value lower

than 20 percent does not appear to be adequate.

The quantity and quality of big sagebrush is important even on strutting grounds (called “leks”) where

the mating rituals are performed. Characteristics of

strutting grounds vary greatly. They may be bare

openings in big sagebrush, gravel pits, plowed fields,

wheat stubble, salt licks, remote air strips, temporary

sheep camps, paved roads, bare exposed ridges, knolls,

small buttes, and dry lake beds (Connelly and others

1981; Roberson 1986; Welch and others 1990). Strutting grounds are not distinctive except that they are

surrounded by big sagebrush. Sagebrush plants surrounding the strutting grounds are of critical importance. These plants are used as escape cover for females coming into the strutting ground. They provide

food and loafing areas for males. The height and

canopy cover values are similar to the characteristics

of sites selected by summering broodless hens and

males.

Sage grouse winter habitats are, like other sage

grouse habitats, strongly traditional. As with nesting

habitat, summering broodless hen habitat, and male

habitat, the birds select wintering areas having greater

than 20 percent canopy cover (Autenrieth 1986; Braun

and others 1977; Eng and Schladweiler 1972; Wallestad

1975a). Connelly and others (2000) suggest 10 to 30

percent. Slope and aspect also play a strong role in

determining winter sage grouse range. Autenrieth

(1986) found that sage grouse selected areas of less

than 15 percent slope and liked southwest exposures.

Hupp and Braun (1989) found feeding activity occurred in drainages and on slopes having south or west

aspect. They recommended that sagebrush be maintained on these areas.

Big sagebrush control projects can have serious

negative impacts on sage grouse (Benson and others

1991; Braun and others 1977; Carr 1968; Fischer and

others 1996; Klebenow 1970; Kufeld 1968; Martin

1970; Peterson 1995; Swenson and others 1987;

Wallestad 1975b). If big sagebrush control is undertaken in areas supporting sage grouse, the guidelines

published by Braun and others (1977) or the method

outlined by Autenrieth (1969) will likely result in

minimizing the impact. These recommendations have

been summarized by Autenrieth (1986) and are reproduced here:

1. The State wildlife agencies should be notified, by

means of an environmental assessment, of each specific proposal to control vegetation a minimum of 2

years in advance of treatment.

2. No control work will be considered where sagebrush cover is less than 20 percent or on steep (20

percent or more gradient) upper slopes with skeletal

soils where big sagebrush is a foot tall or less.

3. The breeding complex (leks and nesting) areas

will be defined as all lands within a 2-mile radius of an

occupied lek. (Connelly and others [1988] and

Wakkinen and others [1992] believe this area needs to

expanded beyond 2 miles.) In areas with poor-quality

nesting habitat, the radius may well exceed 2 miles.

Control of vegetation will not be undertaken within

the breeding complex or on nesting and brood areas.

On-site investigations by land management and State

wildlife agency personnel will be essential to determine inviolate areas. Areas to be protected from treatment will be clearly defined on maps.

4. No control will be attempted in any areas known

to have supported important wintering concentrations of sage grouse within the past 10 years. No

control will be attempted along streams, meadows, or

secondary drainages, both dry and intermittent. A

strip of living sage no less than 400 yards wide will be

retained along the edges of meadows and drainages.

On-site inspections by land management and wildlife

agency personnel will be made to assess the desirability of increasing or decreasing the width of untreated

strips in specific areas.

5. When sagebrush control is found to be unavoidable in sage grouse habitat, all treatment measurements should be applied in irregular patterns using

topography and other ecological considerations to

minimize adverse effects on the sage grouse resource.

Width in treated and untreated areas can vary for the

convenience of application techniques except that
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 53

treated areas should be no wider than 100 yards and

untreated areas will be at least as wide as treated

areas. The untreated areas should not be treated

until food and cover plants in the treated areas attain

a composition comparable to that of the untreated

areas.

6. Where possible, spraying should be done with a

helicopter or ground equipment. No spraying should

be done when wind velocity exceeds 5 miles per hour.

7. Whenever possible, complete kill or removal of

sagebrush in treated areas should be avoided. Partial

kill or removal of sagebrush may enhance the area for

livestock, prevent loss of all snow cover in winter, and

allow for some use of the disturbed area by sage

grouse.

Sage Thrasher, Brewer’s Sparrow, Sage Sparrow—The sage thrasher, Brewer’s sparrow, and sage

sparrow are also considered big sagebrush obligate

species (Belthoff and others 1998; Reynolds and Trost

1981). Their habitat requirements are similar to those

of nesting sage grouse—big sagebrush canopy cover

from 20 to 36 percent (Best 1972; Braun and others

1976; Feist 1968; Grinnell and others 1930; Knick and

Rotenberry 1995; Petersen and Best 1986, 1991;

Reynolds and Trost 1980b, 1981; Rich 1985; Winter

and Best 1985). Walcheck (1970) reported a population of Brewer’s sparrows living in an area of silver

sagebrush (A. cana) having a canopy cover of 53

percent. Dobler (1994, p. 149) stated in his study that

“sagebrush cover density was positively related to

occurrence for seven birds, including sage thrasher,

sage sparrow, and Brewer’s sparrow,” but reported a

lower canopy cover of about 11 percent as being optimum. However, his study area never exceeded 20

percent big sagebrush canopy cover. McAdoo and others (1989) showed greater numbers of sage and Brewer’s

sparrows, and sage thrashers occurring in areas having the highest canopy cover of big sagebrush, but the

cover values of their study areas did not exceed 21

percent. Petersen and Best (1985) studied nest site

selection of sage sparrows in Idaho and reported that

these birds nested where Wyoming big sagebrush

cover was at 23 percent in the vicinity of nests and 26

percent in the general study area. Further, they noted

that all nests were situated in big sagebrush plants

and that large, living shrubs were strongly preferred.

Petersen and Best (1991) reported that Wyoming big

sagebrush canopy cover near sage thrasher’s nests

was 23 percent. Rotenberry (1980) found greater numbers of sage sparrow and western meadow lark

(Sturnella neglecta) on sites with big sagebrush canopy

covers ranging from 25 to 30 percent than for sites with

big sagebrush canopy cover of 0 to 1 percent and 5 to

10 percent.

Sage thrashers place their nests either directly under big sagebrush plants or in big sagebrush plants,

Figure 2.4—Brewer’s sparrow nest in foliage of big

sagebrush (photo by Montana Fish, Wildlife and

Parks Department).

Figure 2.5—Sage sparrow nest hidden (see arrow)

in the foliage of mountain big sagebrush (photo by

Bruce L. Welch).

whereas sage and Brewer’s sparrows place their nests

in big sagebrush plants (fig. 2.4 and 2.5; Best 1972;

Booth 1952; Petersen and Best 1985, 1986, 1991;

Reynolds 1981; Rich 1978a,b, 1980; Schroeder and

Strurges 1975; Winter and Best 1985). Only Walcheck

(1970) observed Brewer’s sparrows nesting in a shrub

other than big sagebrush, that being silver sagebrush.

The diets of these three big sagebrush obligates have

received limited study. Ryser (1985) indicates that

these species feed on insects, spiders, and seeds (see

chapter III for more details concerning insects and
54 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

spiders that are supported by big sagebrush). Petersen

and Best (1986) found that the diet of sage and Brewer’s

sparrow nestlings was entirely of insects and spiders

from early June to late July. For mature Brewer’s

sparrows, Best (1972) reported that insects and spiders were 71 to 81 percent of the June to July items

found in gizzards while seeds made up 8 to 17 percent.

Effects of big sagebrush control are predictably bad

for these three species of birds (Castrale 1982; Knick

and Rotenberry 1995; Reynolds and Trost 1980a,b,

1981). Schroeder and Strurges (1975) found that

Brewer’s sparrows’ use of sprayed big sagebrush

stands was 67 percent lower the first year after

treatment and 99 percent lower for the second year,

than on unsprayed stands. After the third year of

treatment, no nests were found in the sprayed areas.

Similarly, Best (1972) noted a 54 percent reduction in

the use of first-year sprayed stands of big sagebrush

by Brewer’s sparrows. Best (1972) found that 15

percent of the nests were placed in dead big sagebrush plants, 13 percent in what he termed partially

dead (25 to 95 percent dead), and 72 percent in live

plants. Best’s (1972) study was conducted in an area

that had denser populations of Brewer’s sparrows at

42 birds per 100 acres versus 24 birds for the Schroeder

and Strurges (1975) study, perhaps forcing a small

percentage of the birds to nest in dead plants. Further, Schroeder and Strurges (1975) noted that spraying in 100-foot strips was less damaging on Brewer’s

sparrows than whole plot control. Not addressed by

either study was whether or not the increased edge

effect from strip spraying increased nested parasitism (Rich 1978a) by brown-headed cowbirds

(Molothrus ater) and/or nest predation.

Finally, Best (1972) found that Brewer’s sparrows

consumed fewer insects and spiders on controlled

(sprayed with 2,4-D) stands of big sagebrush than on

noncontrolled stands. Fischer and others (1996) noted

fewer insects in treated big sagebrush stands than in

untreated stands.

A study conducted by Reynolds and Trost (1981)

compared the populations of nesting and nonnesting

birds among grazed and ungrazed sites dominated

either by big sagebrush or crested wheatgrass (Agropyron desertorum). They found that sheep grazing did

not alter the density or diversity of nesting bird populations. Density and diversity of birds were greater for

big sagebrush habitat than for the crested wheatgrass

planting. Big sagebrush canopy cover ranged from 17

to 25 percent. Similarly, Bradford and others (1998, p.

13) found that sites converted from big sagebrush to

crested wheatgrass “showed significantly reduced species richness, reduced % shrub obligate species, increased dominance, and increased relative abundance

of horned larks.”

Welch (2002) conducted flushing bird counts between

June 11 and 23 and between the hours of 6: 00 a.m. and

noon on burned big sagebrush sites dominated by

perennial grasses and on unburned big sagebrush

sites. Thirteen paired sites (burned and unburned)

were used in the study. Two pairs were in Oregon, four

in Idaho, three in Utah, two in Wyoming, and two in

Montana. Subspecies of big sagebrush represented in

the study were Wyoming big sagebrush—five sites,

mountain big sagebrush—four sites, and basin big

sagebrush—four sites. Selected pairs had to meet the

following criteria: length of bird flushing transect 1

mile, buffer width 300 feet between the two pairs,

burned sites dominated by perennial grasses, and at

least 20 percent canopy cover of big sagebrush on

unburned sites. Mean number of bird species found on

burned big sagebrush sites was 2.23 and on unburned

big sagebrush sites 7.54. Mean total number of birds

found on burned big sagebrush sites dominated by

perennial grasses was 7.62, and for unburned big

sagebrush sites 37.38.

Petersen and Best (1987, p. 328), studying the effect

of prescribed burning of big sagebrush on nongame

bird, reported: “moderate, incomplete burns are not

detrimental to nongame bird populations nor to important components of sage and Brewer’s sparrow

breeding biology.” Their study was conducted on a 13-

acre plot of which 45 percent (5.85) acres was burned,

which is much smaller than the hundreds of acres

burned reported in the previous study.

Facultative Bird Species

Birds having a facultative association with big sagebrush are listed in table 2.1. For the most part, these

birds do not require as heavy a canopy cover of big

sagebrush as do the obligate species.

One facultative association I found interesting was

the consumption of big sagebrush seed by dark-eyed

juncos (Junco hyemalis), horned larks (Eremophila

alpestris), and white-crowned sparrows (Zonotrichia

leucophrys). I first observed dark-eyed juncos pecking

at mountain big sagebrush inflorescences near Paul

Bunyan’s Woodpile, about 35 miles northeast of Delta,

UT (Welch 1999). They were eating mountain big

sagebrush seeds, which constituted about 70 percent

of their diet (Welch 1999). During this initial observation period, I noticed small footprints around many of

the mountain big sagebrush plants and trails going

from one plant to another (fig. 2.6). This situation is

similar to a sage grouse wintering range, except in

miniature. In addition, seeds and seed bracts were

found on the snow surface. Birds were walking around

pecking in those areas, presumably picking up seeds

that had fallen. I have watched dark-eyed juncos

eating sagebrush seeds at 36 big sagebrush sites from

Fort Hall Indian Reservation, ID; in the north; south

to Salina, UT; Lynndyl, UT, in the west; and east to

Helper, UT. In addition, I have observed the eating of
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 55

Table 2.1—Birds having a facultative association with big sagebrush (Booth

1952; Braun and others 1976; Dumas 1950; Giesen 1997; Grinnell

and others 1930; Linsdale 1938; McEwen and DeWeese 1987;

Medin 1990, 1992; Medin and others 2000; Rasmussen 1941;

Reynolds 1979b; Rich 2001; Ryser 1985; Unknown 1950; Welch

1999, 2002). Common and scientific names are given as listed in the

various cited articles; some repetition.

 Common name Scientific name

American crow Corvus brachyrhynchos

American kestrel Falco sparverius

American pipit Anthus spinoletta rubescens

American robin Turdus migratorius

American rough-legged hawk Buteo lagopus sanctijohannis

Ash-throated flycatcher Myiarchus cinerascen

Barn swallow Hirundo rustica

Black-billed magpie Pica pica hudsonia

Black-headed grosbeak Pheucticus melanocephalus

Black-throated gray warbler Dendroica nigrescens

Black-throated sparrow Amphispiza bilineata deserticola

Blue-gray gnatcatcher Polioptila caerulea

Blue grouse Dendragapus obscurus

Brewer’s blackbird Euphagus cyanocephalus

Broad-tailed hummingbird Selasphorus platycerus platycerus

Brown-headed cowbird Molothrus ater

Burrowing owl Athene cunicularia

Bushtit Psaltriparus minimus plumbeus

California linnet Carpodacus mexicanus frontalis

California quail Callipepla californica

California shrike Lanius ludovicianus gambeli

Calliope hummingbrid Stellula calliope

Canyon wren Catherpes mexicanus

Cassin’s finch Carpodacus cassinii

Chipping sparrow Spizella passerina

Chukar Alectoris chukar

Clark’s nutcracker Nucifraga columbiana

Cliff swallow Hirundo pyrrhonota

Columbian sharp-tailed grouse Tympanuchus phasianellus columbianus

Common nighthawk Chordeiles minor

Common poorwill Phalaenoptilus nuttallii

Common raven Corvus corax

Common redpoll Acanthis linaria linaria

Cooper’s hawk Accipiter cooperii

Dark-eyed junco Junco hyemalis

Evening grosbeak Coccothraustes vespertinus

Ferruginous hawk Buteo regalis

Gray flycatcher Empidonax griseus

Golden eagle Aquila chrysaetos canadensis

Great horned owl Bubo virginianus

Green-tailed towhee Chlorura chlorura

Hermit thrush Catharus guttatus

Horned lark Eremophila alpestris

House finch Carpodacus mexicanus

House wren Troglodytes aedon parkmanii

Lark bunting Calamospiza melanocorys

Lark sparrow Chondestes grammacus

Lazuli bunting Passerina amoena

Loggerhead shrike Lanius ludovicianus

Long-eared owl Asio otus

Marsh hawk Circus hudsonius

MacGillivray’s warbler Oporornis tolmiei

Mountain bluebird Sialia currucoides

Mountain chickadee Parus gambeli

(con.)
56 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Mountain quail Oreortyx pictus

Montana junco Junco oregonus montanus

Mourning dove Zenaida macroura

Northern harrier Circus cyaneus

Northern mockingbird Mimus polyglottos

Northern shrike (Northwestern) Lanius borealis invictus

Nuttall poor-will Phalaenoptilus nuttalli nuttalli

Olive-sided flycatcher Contopus borealis

Pacific nighthawk Chordeiles minor hesperis

Pinyon jay Cyanocephalus cyanocephalus

Prairie falcon Falco mexicanus

Red-tailed hawk Buteo borealis calurus

Ring-necked pheasant Phasianus colchicus

Rock wren Salpinctes obsoletus

Rough-winged swallow Riparia riparia

Scaled quail Callipepla squamata

Say’s phoebe Sayornis saya saya

Sharp-tailed grouse Pedioecetes phasianellus

Short-eared owl Asio flammeus flammeus

Sparrow hawk (American kestrel) Falco sparverius

Spotted towhee Pipilo maculatus

Swainson hawk Buteo swainsoni

Turkey vulture Cathartes aura septentrionalis

Vesper sparrow Pooecetes gramineus confinis

Violet-green swallow Tachycineta thalassina lepida

Virginia warblers Vermivora virginiae

Western bluebird Sialia mexicana occidentalis

Western burrowing owl Specotyto cunicularia hypugaea

Western crow Corvus brachyrhynchos hesperis

Western flycatcher Empidonax difficilis

Western kingbird Tyrannus verticalis

Western lark sparrow Chondestes grammacus strigatus

Western meadowlark Sturnella neglecta

Western mockingbird Mimus polygottos leucopterus

Western savannah sparrow Passerculus sandwichensis alaudinus

White-crown sparrow (Gambel sparrow) Zonotrichia leucophrys

White-throated swift Aeronautes saxatalis saxatalis

Table 2.1 (Con.)

 Common name Scientific name

Figure 2.6—Footprints (arrow) of

dark-eyed juncos feeding on big

sagebrush seeds in the snow (photo

by Bruce L. Welch).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 57

big sagebrush seeds by horned larks (seven big sagebrush sites) and white crown sparrows (fig. 2.7; 11 big

sagebrush sites).

Consumption of seeds occurred from early December to late February. In May 1992, dark-eyed juncos

were observed flying in and out of an open shed that

was being used to dry big sagebrush inflorescences

that had been collected the previous winter. Inside the

shed, the birds were scratching and pecking around,

among, and through the inflorescences. A pile of big

sagebrush seeds (about 50 g) was placed near the

layers of drying inflorescences. In less than a day, the

entire pile was consumed by the birds, thus proving

that they will consume big sagebrush seeds at a time

other than winter. The importance of big sagebrush

seeds in the yearly diet of these birds is unknown.

Probably more important than the absolute amount

eaten is the timing when the birds are eating the

seeds. After fresh snow, big sagebrush seed may be the

only food available to these birds (fig. 2.8). Nutritive

value of big sagebrush seeds collected near the Paul

Bunyan’s Woodpile is given in chapter IV.

While conducting a pygmy rabbit (Sylvilagus

idahoensis or Brachylagus idahoensis) survey just

west of Utah Lake, I observed over the course of the

survey—March 10 to 26, 2003—three distinct flocks of

5 to 10 red-winged blackbirds (Agelaius phoeniceus) in

the big sagebrush stand. They were feeding on a

bounteous supply of insect larvae. What was most

curious to me was the fact they were not feeding on the

same insect larvae present in a patch of grass located

closer to the lake. Apparently, the big sagebrush

plants were providing security cover for the birds.

Figure 2.7—White-crown sparrow feeding on basin

big sagebrush seeds. Arrow pointing to bird feeding

on seeds. All three birds were observed eating basin

big sagebrush seeds (photo by Bruce L. Welch).

Figure 2.8—Dark-eyed junco feeding on Wyoming

big sagebrush seeds (photo by Bruce L. Welch).

Mammals ______________________

Small Mammals

Pygmy Rabbit—Pygmy rabbits (Sylvilagus

idahoensis or Brachylagus idahoensis) are the sage

grouse of the mammalian world in that they have an

obligate relationship with big sagebrush (Green and

Flinders 1980b; Janson 2002; Lyman 1991; Peterson

1995). As the name implies, they are the smallest of

North American rabbits. They are endemic to the

Great Basin and adjacent Intermountain areas of the

Western United States (Campbell and others 1982;

Green and Flinders 1980b; Janson 2002; Weiss and

Verts 1984). They typically associate with dense stands

of big sagebrush where the soils are deep and

excavatable (Borell and Ellis 1934; Campbell and

others 1982; Gabler and others 2001; Gates and Eng

1983; Green and Flinders 1980a; Grinnell and others

1930; Janson 2002; Orr 1940; Pritchett and others

1987; Severaid 1950; Weiss and Verts 1984). Where

vegetative habitat needs are met, pygmy rabbits dig

relatively shallow burrows with two or more entrances

(Janson 2002). With sufficient big sagebrush cover,

soil characteristics such as depth and ease of digging

are determining factors in the distribution of these

rabbits and not the presence of specific subspecies of

big sagebrush (Weiss and Verts 1984).
58 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Early workers (Borell and Ellis 1934; Grinnell and

others 1930; Orr 1940; Severaid 1950) found the rabbits in the tallest and densest big sagebrush or heaviest patches of big sagebrush available. Severaid (1950,

p. 3) observed: “These rabbits stay constantly under

brush canopy and will not run if one walks through

their domain.” They are elusive rabbits. Campbell and

others (1982, p. 100) stated: “Our observations at both

sites showed B. idahoensisprimarily confined to dense

stands of big sagebrush growing in deep soils of drainages and hollows.” Pygmy rabbits occupy stands of big

sagebrush having canopy cover ranging from 16 to 46

percent—similar to the needs of sage grouse (Dobler

and Dixon 1990; Gates and Eng 1983; Green and

Flinders 1980b; Weiss and Verts 1984). Katzner and

Parker (1997) found that wintering areas of highest

pygmy rabbit use were in basin big sagebrush stands

having a canopy cover of 51.1 percent, compared to

areas of medium use of 42.7 percent canopy cover, and

to areas of low use of 38.6 percent.

Big sagebrush is also a prime food source (Orr 1940).

Green and Flinders (1980b) reported that pygmy rabbits consume big sagebrush and possibly three-tip

sagebrush year round. They found that 51 percent of

the summer diet was sagebrush, and this increased to

99 percent in the winter. Gates and Eng (1983) noted

that the amount of big sagebrush in the diet of pygmy

rabbits for July, August, September, November, and

December was 30, 9, 52, 89, and 91 percent, respectively. In feeding trials of captive animals, White and

others (1982) reported that the rabbits showed no

significant preference for one subspecies of big sagebrush over another.

Sagebrush Vole—Another mammal that is considered a big sagebrush obligate by most researchers is

the sagebrush vole (Lagurus curtatus; Carroll and

Genoways 1980; Larrison and Johnson 1973; Marshall

1985; McEwen and DeWeese 1987; Rickard 1960),

although Maser and Strickler (1978) found a population inhabiting a grassy area in southeastern Oregon.

Sagebrush voles are normally found in “heavy sagebrush” and locate their burrows beneath stumps of the

largest big sagebrush plants (Borell and Ellis 1934).

Oldemeyer and Allen-Johnson (1988) suggest big sagebrush canopy cover in sagebrush voles’ habitat was 52

to 55 percent. Sagebrush voles feed upon the leaves of

big sagebrush, which may also serve as a source of

water, especially in late summer and early autumn,

when forbs and grasses are desiccated (Borell and

Ellis 1934; James and Booth 1954; Parmenter and

others 1987).

Populations of sagebrush voles are dynamic. At

times they may be abundant and then suddenly disappear (Moore 1943). They do not accept baits readily,

which could result in low estimates of populations

(Johnson and others 1948). Unlike other species of

voles, sagebrush voles appear not to damage big sagebrush plants (Frischknecht and Baker 1972; Mueggler

1967; Parmenter and others 1987). The long-tailed

vole (Microtus longicaudus), mountain vole (M.

montanus), and meadow vole (M. pennsylvanicus) can

cause extensive damage and death (10 to 84 percent

kill) to big sagebrush plants over areas of 50 to 1,200

acres (Frischknecht and Baker 1972; Mueggler 1967;

Parmenter and others 1987).

While conducting a survey (April 2004) for the presence of pygmy rabbits south and east of Deer Creek

Reservoir in central Utah, I noted girdling of big

sagebrush plants by small rodents (most likely longtailed voles-Microtus longicaudus). There were several occasions where a big sagebrush plant was girdled

but an adjacent nonsagebrush woody shrub showed no

signs of being girdled. It was clear that the small

rodents preferred girdling big sagebrush over the

following shrub species: antelope bitterbrush

(Purshia tridentata), choke cherry (Prunus virginiana), Gambel oak (Quercus gambelii), rubber rabbitbrush (Chrysothamnus nauseosus), and serviceberry

(Amelanchier utahensis). Differential preference was

more than likely due to the ease of peeling big sagebrush bark as compared to the other shrub species.

Other Small Mammals—Parmenter and others

(1987) observed that deer mouse (Peromyscus

maniculatus) nests were made almost entirely from

strips of big sagebrush bark. Borell and Ellis (1934),

Grinnell and others (1930), and Linsdale (1938) also

reported that the bushy-tailed wood rat (Neotoma

cinerea) uses big sagebrush bark as well as other

materials in nest construction. James and Booth (1954),

Johnson and others (1948), Moore (1943), and Mullican

and Keller (1986, 1987) have reported that sagebrush

voles made extensive use of big sagebrush bark for

nesting material.

Small mammals having a facultative association

with big sagebrush are listed in table 2.2 (Welch and

Criddle 2003; fig. 2.9). The table lists about 79 species,

of which the inclusion of pikas came as a surprise. My

literature search resulted in two references where

pikas were either feeding on big sagebrush or making

“hay” out of big sagebrush. Severaid (1950, p. 4) noted:

“The pikas lives in the rock talus of the abandoned

mine dumps and feeds on the Artemisia wherein

dwells the pigmy rabbit.” Linsdale (1938, p. 196)

observed the following concerning pikas: “At 2 places,

at least, there were accumulation of freshly cut green

branches of brushes such as surrounded the rock

slides. At 1 place were seen branches of Artemisia,

Chrysothamnus, Symphoricarpos, Ribes, and an herbaceous plant.”

Table 2.3 lists effects of big sagebrush control treatments on individual species of small mammals. Of the

25 species listed, only four showed positive response to
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 59

Table 2.2—Mammals having a facultative association with big sagebrush (Allred

1973; Borell and Ellis 1934; Clary and Medin 1993; Doering and Keller

1998; Gray 1943; Kirkland and others 1997; Knick and Dyer 1997;

Larrison and Johnson 1973; Linsdale 1938; Longland 1995; McAdoo

and Young 1980; McEwen and DeWeese 1987; McGee 1982; O’Farrell

1974; Oldemeyer and Allen-Johnson 1988; Orr 1940; Ports and

George 1990; Ports and McAdoo 1986; Priday and Luce 1999;

Reynolds 1979b, 1980; Rickard 1960; Root and others 2001; Scheffer

1941, Severaid 1950; Sherwin and others 2000; Smith and Urness

1984; West 1983a; Williams 1984; Yensen and others 1989). Common and scientific names are given as listed in the various cited

articles; some repetition.

Common name Scientific name

Antelope ground squirrel Citellus leucurus leucurus

Badger Taxidea taxus taxus

Big brown bat Eptesicus fuscus

Bison Bison bison

Black hills cottontail Sylvilagus nuttallii grangeri

Black-tailed jackrabbit Lepus californicus deserticola

Bobcat Felis rufus

Boreal redback vole Clethrionomys gapperi

Bushy-tailed woodrat Neotoma cinerea cinerea

California little brown bat Myotis californicus californicus

Canyon mouse Peromyscus crinitus crinitus

Chisel-toothed kangaroo rat Dipodomys microps

Columbian kangaroo rat Dipodomys ordii columbianus

Cottontail rabbit Syvilagus nuttalii grangeri

Coyote Canis latrans lestes

Dark kangaroo mouse Microdipodops megacephalus

Deer mouse Peromyscus maniculatus

Desert cottontail Sylvilagus audubonii

Desert harvest mouse Reithrodontomys megalotis megalotis

Desert shrew Notiosorex crawfordi

Desert woodrat Neotoma lepida

Dwarf shrew Sorex nanus

Elk Cervus elaphus

Fisher pocket gopher Thomomys quadratus fisheri

Gaspe shrew Sorex lyelli

Golden-mantled squirrel Spermophilus lateralis

 Callosperophilus lateralis

Gray fox Urocyon cinereoargenteus

Great Basin kangaroo rat Dipodomys microps

Great Basin pocket mouse Perognathus parvus olivaceusa

Harvest mouse Reithrodontomys megalotis megalotis

Inyo chipmunk Eutamias quadrivittatus

Kit fox Vulpes macrotis

Least chipmunk Eutamias minimus

 Tamias minimus

Little pocket mouse Perognathus longimembris

Long-eared myotis Myotis evotis

Long-legged myotis Myotis volans

Longtail pocket mouse Perognathus formosus

Longtail vole Microtus longicaudus

Longtail weasel Mustela frenata

Malheur shrew Sorex preblei

Masked shrew Sorex cinerus

Merriam’s kangaroo rat Dipodomys merriami

Merriam’s shrew Sorex merriami

Montane shrew Sorex monticolus

Mountain vole Microtus montanus

Mule deer Odocoileus hemionus

Nevada ground squirrel Citellus elegans nevadensis

Northern grasshopper mouse Onychomys leucogaster

Northern pocket gopher Thomomys talpoides

(con.)
60 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 2.2 (Con)

Common name Scientific name

Ord kangaroo rat Dipodomys ordii

Oregon ground squirrel Citellus oregonus

Pallid big brown bat Eptesicus fuscus pallidus

Panamint kangaroo rat Dipodomys panamintinus

Pika Ochotona schisticeps

 Ochotona princeps

Pinyon mouse Peromyscus truei

Paiute ground squirrel Citellus townsendi mollis

Porcupine Erethizon dorsatum

Pronghorn Antilocapra americana

Red fox Vulpes vulpes

Richardson’s ground squirrel Spermophilus richardsonii

Sagebrush chipmunk Eutamias minimus pictus

Sagebrush ground squirrel Spermophilus townsendii artemisiae

Short-tailed grasshopper mouse Onychomys leucogaster brevicaudus

Shorttail weasel Mustela erminea

Sonoran white-footed mouse Peromyscus maniculatus sonoriensis

Shrew Sorex monticolus

Southern grasshopper mouse Onychomys torridus

Spotted bat Euderma maculatum

Striped skunk Mephitis mephitis

Thirteen-lined ground squirrel Spermophilus tridecemlineatus

Townsend’s big-eared bat Corynorhinus townsendii

Townsend’s ground squirrel Spermophilus townsendii

Uinta ground squirrel Spermophilus armatus

Uinta pocket mouse Perognathus parvus idahoensis

Vagrant shrew Sorex vagrans

Wasatch chipmunk Eutamias minimus consorbrinus

Washington ground squirrel Spermophilus washingtoni

Western cottontail Sylvilagus nuttallii grangeri

Western harvest mouse Reithrodontomys megalotis

Western jumping mouse Zapus princeps

Western spotted skunk Spilogale gracilis

White-foot mouse Peromyscus maniculatus sonoriensis

White-tailed antelope ground squirrel Ammospermophilus leucurus

White-tailed jackrabbit Lepus townsendii townsendii

White-tailed prairie dog Cynomys leucurus

Wyoming pocket mouse Perognathus fasciatus

Yellow-haired porcupine Erethizon epixanthum epixanthum

Yuma myotis Myotis yumanensis

a

McEwen and DeWeese (1987) listed this species as an obligate of big sagebrush.

Figure 2.9—Cottontail living in

Wyoming big sagebrush (photo

Bruce L. Welch).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 61

Table 2.3–Effects of big sagebrush control treatments on individual species of small mammals. A minus sign means the control

treatment had a negative effect; a plus sign means the treatment had a positive effect.

Species Effects of control Reference

Badger holes – Ritchie and others 1994

Taxidea taxus

Black-tailed jackrabbit – Reynolds and Trost 1980b

Lepus californicus – Nydegger and Smith 1986

Boreal redback vole – McGee 1982

Clethrionomys gapperi

Bushytail woodrat – Reynolds and Trost 1980b

Neotoma cinerea

Chisel-toothed kangaroo rata – Larrison and Johnson 1973b

Dipodomys microps

Deer mouse – Reynolds 1980

Peromyscus maniculatus – Smith and Urness 1984b

+ Longland 1994

+ McGee 1982

– Larrison and Johnson 1973b

– Rickard 1960c

– Koehler and Anderson 1991

– Reynolds and Trost 1980b

Desert kangaroo rat + Longland 1995

Dipodomys deserti + Longland 1994

Golden-mantled squirrel – Longland 1994

Spemophilus lateralis

Great Basin pocket mouse – Reynolds 1980

Perognathus parvus – Smith and Urness 1984b

– Longland 1994

– Rickard 1960c

Lagomorph pellets – Ritchie and others 1994

Least chipmunk – Reynolds 1980

Eutamias minimus – Smith and Urness 1984b

– McGee 1982

– Larrison and Johnson 1973b

– Reynolds and Trost 1980b

Longtail weasel – McGee 1982

Mustela frenata – Reynolds and Trost 1980b

Little pocket mouse + Longland 1995

Perognathus longimembris + Longland 1994

Merriam’s kangaroo rat – Longland 1995

Dipodomys merriami – Longland 1994

Mountain cottontail – Reynolds and Trost 1980b

Sylvilagus nuttalli

Mountain vole – McGee 1982

Microtus montanus + Koehler and Anderson 1991

Northern grasshopper mouse – Reynolds 1980

Onychomys leucogaster – Reynolds and Trost 1980b

Northern pocket gopher – McGee 1982

Thomomys talpoides

Ord kangaroo rat + Longland 1995

Dipodomys ordii + Longland 1994

– Larrison and Johnson 1973b

+ Koehler and Anderson 1991

– Reynolds and Trost 1980b

Panamint kangaroo rat + Longland 1995

Dipodomys panamintinus + Longland 1994

Pinyon mouse – Smith and Urness 1984b

Peromyscus truei

Sagebrush vole – Reynolds 1980

Lagurus curtatus – Smith and Urness 1984b

– Rickard 1960c

Townsend’s ground squirrel – Nydegger and Smith 1986

Spermophilus townsendii – Reynolds 1980

Uinta ground squirrel + McGee 1982

Spermophilus armatus

Vagrant shrew – McGee 1982

Sorex vagrans

Western harvest mouse + Reynolds 1980

Reithrodontomys megalotis + Smith and Urness 1984b

– Longland 1994

+ Larrison and Johnson 1973b

– Rickard 1960c

Western jumping mouse – McGee 1982

Zapus princeps

White-tailed antelope ground squirrel – Longland 1995

Ammospermophilus leucurus – Longland 1994

a

Known as the Great Basin kangaroo rat in some of the literature.

b

I use only the crested wheatgrass and sagebrush values in this table.

c

Study was a comparison between big sagebrush/Agropyron and Agropyron/Poa vegetation type and not a control versus noncontrol treatment.
62 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

control of big sagebrush, four species were mixed

(that is, some studies showed a positive response,

while other studies showed a negative response), and

17 species showed a negative response to the controlling of big sagebrush. Reynolds and Trost (1980b, p.

122) stated: “Crested wheatgrass plantings, regardless of sheep use, supported fewer nesting bird species

and a lower density of birds, mammals, and reptiles

than did areas dominated by [big] sagebrush.” Clary

and Medin (1993) reported similar observations.

Longland and Bateman (2002) observed that small

mammal species richness was greatest in undisturbed

big sagebrush, intermediate in big sagebrush islands,

and lowest in burned big sagebrush habitats. This lack

of a positive response to big sagebrush control for so

many species is interesting when one considers that

big sagebrush comprises for the most part little of the

diet of these animals (table 2.4). It appears that big

sagebrush’s main function for many small mammals

is cover (Longland 1991; McAdoo and others 1987).

Table 2.4—Small mammals reported as consumers of big sagebrush. Common and scientific names are

given as listed in the various cited articles; some repetition.

Species

 Common name Scientific names Diet Reference

Percent

Black-tailed jackrabbit Lepus californicus ? Severaid 1950

? McAdoo and Young 1980

Black-tailed hare 10 Uresk 1978

Black-tailed jackrabbit 1–8 MacCracken and Hansen 1984

6–21 Fagerstone and others 1980

? McKeever and Hubbard 1960

8 Gates and Eng 1983

Chisel-toothed

kangaroo rat Dipodomys microps 5 Johnson 1961

Deer mouse Peromyscus maniculatus ? Parmenter and others 1987

Least chipmunk Eutamias minimus 2 Johnson 1961

Long-tailed vole Microtus longicaudus ? Parmenter and others 1987

Ord’s kangaroo rat Dipodomys ordi 3 Johnson 1961

Pika Ochotona princeps ? Severaid 1950

Pika Ochotona schisticeps ? Linsdale 1938

Pygmy rabbit Sylvilagus idahoensis ? Severaid 1950

Brachylagus idahoensis 51–99 Green and Flinders 1980a b

Sagebrush vole Lagurus curtatus ? Rickard 1960

? Parmenter and others 1987

Lemmiscus curtatus 1 Mullican and Keller 1986

Townsend’s ground Spermophilus idahoensis ? Rogers and Gano 1980

squirrel Citellus townsendi 2 M. Johnson 1977

? Rickart 1987

? Davis 1939

? Maser 1974

Western cottontail Sylvilagus nuttallii ? Severaid 1950

Nuttall cottontail 3–4 MacCracken and Hansen 1984

Western harvest mouse Reithrodontomys megalotis 12 Johnson 1961

White-tailed jackrabbit Lepus townsendi ? Severaid 1950

? McAdoo and Young 1980

Food items are then furnished by the understory

species of grasses, forbs, and insects.

So what would be the optimal big sagebrush canopy

cover for most small mammals? This likely varies by

species, but studies generally support at least 20

percent or more, which is greater than the 15 percent

or less advocated by Baxter (1996). Listed in table 2.5

are big sagebrush canopy cover percentages for various studies conducted on small mammals occurring in

big sagebrush ecosystem. Canopy cover ranged from 0

to 68 percent.

The Allred (1973) study, of special interest, describes the ecological distribution and relative abundance of small mammals in 12 plant communities

varying in big sagebrush canopy cover from 0 to 68

percent. The plant community with 68 percent big

sagebrush canopy cover had a relative abundance

index of 34 with six species living in the community

(deer mouse, Ord kangaroo rat, Dipodomys ordi; Great

Basin pocket mouse, Perognathus parvus; northern
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 63

Table 2.5—Percentage of canopy cover of big sagebrush for various small mammal habitats. Common and

scientific names are given as listed in the various cited articles; some repetitions.

Species

 Common name Scientific names Canopy Reference

Percent

Black-tailed hare Lepus californicus 9, 33 Uresk 1978

Boreal redback vole Clethrionomys gapperi 48–50 McGee 1982

Deer mouse Peromyscus maniculatus 16–23 Nichols and others 1975

0–68 Allred 1973

52–55 Oldemeyer and Allen-Johnson 1988a

48–50 McGee 1982

29 Mullican and Keller 1986

Golden-mantled squirrel Spermophilus townsendii 52–55 Oldemeyer and Allen-Johnson 1988a

Great Basin pocket mouse Perognathus parvus 16–23 Nichols and others 1975

0–68 Allred 1973

52–55 Oldemeyer and Allen-Johnson 1988a

Tamias minimus 29 Mullican and Keller1986

Least chipmunk Eutamias minimus 16–23 Nichols and others 1975

0–68 Allred 1973

52–55 Oldemeyer and Allen-Johnson 1988a

48–50 McGee 1982

29 Mullican and Keller 1986

Long-tailed weasel Mustela frenata 48–50 McGee 1982

Merriam’s shrew Sorex merriami 0–30 Allred 1973

29 Mullican and Keller 1986

Mountain vole Microtus montanus 48–50 McGee 1982

29 Mullican and Keller 1986

Northern grasshopper

mouse Onychomys leucogaster 0–68 Allred 1973

29 Mullican and Keller 1986

Northern pocket gopher Thomomys talpoides 48–50 McGee 1982

Ord kangaroo rat Dipodomys ordii 0–68 Allred 1973

29 Mullican and Keller 1986

Pygmy rabbit Brachylagus idahoensis 19 Green and Flinders 1980a,b

Sylvilagus idahoensis 16–33 Weiss and Verts 1984

39–51 Katzner and Parker 1997

Sagebrush vole Lagurus curtatus 52–55 Oldemeyer and Allen-Johnson 1988a

Lemmiscus curtatus 29 Mullican and Keller 1986

Townsend’s ground

squirrel Spermophilus townsendii 0–50 Allred 1973

52–55 Oldemeyer and Allen-Johnson 1988a

29 Mullican and Keller 1986

Uinta ground squirrel Spermophilus armatus 48–50 McGee 1982

Vagrant shrew Sorex vagrans 48–50 McGee 1982

Western harvest mouse Reithrodontomys megalotis 16–23 Nichols and others 1975

0–68 Allred 1973

29 Mullican and Keller 1986

Western jumping mouse Zapus princeps 48–50 McGee 1982

a

Not able to differentiate between the cover contributed by big sagebrush and other shrubs.

grasshopper mouse, Onychomys leucogaster; least chipmunk, Eutamias minimus; western harvest mouse,

Reithrodontomys megalotis). This relative abundance

index ranked second to last, with only the Juniperus

site at 0 percent big sagebrush canopy cover lower at

11. For sites having 0 percent big sagebrush canopy

cover and high amounts of grasses and forbs, the

relative abundance index was 140 for the Elymus-forb

site with seven species, and 160 for the OryzopsisStipa site with four species. These compare to the four

highest sites: (1) Artemisia-Chrysothamnus-grass site

at 218 with seven species and 50 percent canopy cover

of big sagebrush; (2) Chrysothamnus-Tetradymia-Artemisia site at 219 with six species and 20 percent
64 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

canopy cover of big sagebrush; (3) ChrysothamnusArtemisia site at 269 with eight species and 30 percent

canopy cover of big sagebrush; and (4) ChrysothamnusArtemisia-grass site at 346 with nine species and 24

percent canopy cover of big sagebrush. From this study,

canopy cover of big sagebrush that appears to support the

greatest number of species is between 20 and 50 percent.

McGee (1982) compared small mammal population

response to burned and unburned big sagebrush habitat. The unburned big sagebrush habitat had a canopy

cover of 49 percent. Deer mouse and Uinta ground

squirrel (Spermphilus armatus) were the only species

out of nine to show a positive response to fall burning

of big sagebrush. Other studies that lend support to

the Allred (1973) and McGee (1982) studies are Nichols

and others (1975); Oldemeyer and Allen-Johnson

(1988); and Smith and Urness (1984). From these

studies it appears that big sagebrush canopy cover

favoring small mammals ranges from 20 to 50 percent.

Such consideration for sagebrush does not exclude

the importance of understory plants (grasses and

forbs) and insects that supply the food for most of the

small mammals of the big sagebrush ecosystem

(Koehler and Anderson 1991; Smith and Urness 1984).

Large Mammals

Pronghorn—Pronghorn (Antilocapra americana)

is a facultative associate of big sagebrush (fig. 2.10;

Mace 1956; Peterson 1995; Welch and Criddle 2003;

Yoakum 1986). This native antelope occupies vegetative types ranging from shortgrass prairie to shrubsteppe to salt-desert shrublands. Yoakum and others

(1996) estimate that 68 percent of the pronghorns

inhabit grassland and 32 percent shrubland.

Sundstrom and others (1973) reported that 51 percent

of pronghorns in Wyoming inhabited a combination of

sagebrush steppe, saltbush-greasewood, and wheatgrassneedlegrass shrubsteppe, while 49 percent inhabited

grama-needlegrass-wheatgrass, wheatgrassneedlegrass, and grama-buffalo grass ranges. The significance in these values is that Wyoming has probably

the largest expanse of unaltered big sagebrush habitat

(Sundstrom and others 1973) in North America and by

far the largest number of pronghorns—58 percent of

the world’s population (Sundstrom and others 1973;

Yoakum and others 1996). In fact, Wyoming and

Montana account for about 73 percent of all the pronghorn in the world (Yoakum and others 1996). A study

conducted in central Montana by Bayless (1969) found

the distribution of pronghorn to be 55 percent on

shrublands, 31 percent on grasslands, and 13 percent

on cropland during the summer. He found the winter

distribution to be 93 percent on shrublands, 5 percent

on grasslands, and 2 percent on croplands. These

values are supported by the observations of Pyrah and

Schlatterer (1968) as reported by Sundstrom and

others (1973, p.17): “They reported that the sagebrush-grassland type received the greatest use, both

in summer and winter.” Sundstrom and others (1973)

reported that 69 percent of the pronghorns in southeastern Montana were found on sagebrush-grassland

type.

Regardless of the division of pronghorns among

grasslands, shrublands, and other vegetative types,

when pronghorns are on grasslands, they search the

habitat for shrubs and forbs to eat (table 2.6). Shrubs

dominate the diet year long with forbs being heavily

used during spring and matching shrubs in summer

(Pyrah 1987). On the other hand, grasses are used

sparingly throughout the year (Pyrah 1987; Smith and

Beale 1980).

Several studies show that two species of shrubs,

Wyoming big sagebrush and silver sagebrush, are

associated with higher reproductive levels of pronghorn than that of grasslands. Martinka (1967, p. 159)

reported the following for north-central Montana:

Winter mortality of pronghorn antelopes was studied

near Glasgow, Montana, in April 1965. A minimum loss

of 500 pronghorns was associated with severe weather

and occurred primarily on foothill grassland along the

Milk River. Comparisons of rumen samples with feeding site examinations found that starvation occurred

while animals were restricted to the grassland vegetative type. Among pronghorns in the Glasgow herd, fawn

production was 39-55 fawns per 100 does as compared

to a normal 90-110. On the Malta winter range in the

adjacent county to the west where sagebrush was

abundant, available, and heavily utilized, losses were

minor and fawn production normal.

Sundstrom and others (1973, p. 34), citing a variety of

reports and letters, stated:

As the pronghorn populations radiate farther from the

primary ranges of these two sagebrush species, the

average number of fawns per 100 does decreased significantly. In western South Dakota where the foregoing two plant species are abundant, fawn: doe ratios

Figure 2.10—Pronghorn—Flaming Gorge Reservoir, Utah—

that consumes large quantities of Wyoming big sagebrush year

round (photo by Bruce L. Welch).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 65

Table 2.6—Food habits of pronghorn (Antilocapra americana). Data expressed as a

percentage of diet.

Season Shrubs Forbs Grasses Reference

- - - - - - - - - - Percent - - - - - - - - - -

Winter 75 24 1 Bayless 1969

Spring 78 00 22 Bayless 1969

Winter 59 31 6 Martinka 1967

Spring 80 18 2 Smith and Beale 1980

Summer 63 36 1 Smith and Beale 1980

Fall 96 3 1 Smith and Beale 1980

? 66 31 3 Einarsen 1948

Fall 69 18 1a Einarsen 1948

Summer 63 26 0a Einarsen 1948

Spring 66 33 1 Mason 1952

Summer 48 52 0 Mason 1952

Fall 72 28 0 Mason 1952

Fall 66 12 20a Mitchell and Smoliak 1971

Winter 53 21 26 Mitchell and Smoliak 1971

Summer 47 43 1 Johnson 1979b

Winter 77 1 2 Johnson 1979b

Spring 25 51 20a Hoover and others 1959

Summer 22 66 1a Hoover and others 1959

Fall 72 22 1a Hoover and others 1959

Winter 54 26 5a Hoover and others 1959

Spring 63 35 2 Ferrel and Leach 1952

Fall 47 52 1 Ferrel and Leach 1952

Winter 96 2 2 Ferrel and Leach 1952

Fall 87 6 7 Couey 1946

Spring 58 42 0 Smith and Malechek 1974c

Summer 55 45 0 Smith and Malechek 1974c

Fall 70 28 2 Smith and Malechek 1974c

Spring 76 23 1 Smith and Malechek 1974d

Summer 75 25 0 Smith and Malechek 1974d

Fall 77 30 0 Smith and Malechek 1974d

Yearly 76 23 1 Gates and Eng 1983

Spring 37 47 16 McInnis and Vavra 1987

Summer 15 79 6 McInnis and Vavra 1987

Fall 56 31 13 McInnis and Vavra 1987

Winter 60 21 19 McInnis and Vavra 1987

Spring 64 34 2 Ferrel and Leach 1950

Summer 47 50 1a Ferrel and Leach 1950

Yearly 88 11 1 Olsen and Hansen 1977

Spring 76-91 — — Ngugi and others 1992

Summer 80-90 — — Ngugi and others 1992

Fall 80-90 — — Ngugi and others 1992

Spring 11 11 78 Dirschl 1963e

Summer 40 55 5 Dirschl 1963e

Fall 55 42 1a Dirschl 1963e

Winter 85 7 1a Dirschl 1963e

Spring 66 26 8 Dirschl 1963f

Summer 45 52 1a Dirschl 1963f

Fall 87 12 1 Dirschl 1963f

Winter 83 8 0a Dirschl 1963f

Year long 71 22 7 Yoakum 1983

Year long 63 34 3 Sundstrom and others 1973

a

If values do not sum to 100, percentages for agricultural crops or unknowns were not included in

this table. b

Data from this study were expressed as relative densities (percent) of plant fragments in feces.

C

Values from Awapa Plateau.

d

Values from Desert Experimental Range.

e

Values from Cypress Hills.

f

Values from Matador.
66 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

were approximately 100: 100. Along the Missouri River

in the same state, Wyoming big sagebrush and silver

sagebrush are much less abundant; there, average

fawn: doe ratios were 50: 100. In Montana, well within

the primary range of Wyoming big sagebrush and silver

sagebrush, the average fawn: doe ratio was 90: 100. Yet,

when some of these same antelope were transplanted

from Montana to Kansas, where there were no large,

woody sagebrush species, and general environmental

conditions were different, reproduction decreased within

a few years to 52 fawns per 100 does.

They reported similar results for the Sand Hills of

Nebraska, Idaho, and New Mexico. These reports

contrast with the view of Yoakum and others (1996),

which is that pronghorn are more productive on grasslands than shrublands.

Martin and others (1951) described big sagebrush as

an outstanding pronghorn food that is eaten throughout the year. The amount of big sagebrush in the diet

of pronghorn varies, with the most occurring during

the winter and spring and lesser amounts in the fall

and lowest in the summer months. Details are given in

table 2.7.

Smith and others (1965) fed six pronghorn, cafeteria

style (free choice), 16 species of shrubs that occur

commonly on desert ranges of Utah. Big sagebrush

was the number one diet item and made up 55 percent

of the diet. Black sagebrush was second at 21 percent

of the diet.

Last, Autenrieth and Fichter (1975) point out the

importance of big sagebrush as cover for parturient

does and for fawns in the Pahsimeroi drainage of

Idaho. Pyrah (1987) records similar observations for

Yellow Water Triangle area of Montana.

Mule Deer—The mule deer (Odocoileus hemionus)

is a facultative associate of big sagebrush, which

provides food (fig. 2.11), cover during fawning, and

cover for fawns (fig. 2.12) and adults (Martin and

others 1951; Peterson 1995; Robinette 1972; Welch

and Criddle 2003). The utilization of the current year’s

growth of big sagebrush varies (Anderson and others

1972; Elderkin and others 1986; Grimm 1939; Hoskins

and Dalke 1955; Van Dersal 1938; Wambolt 2001;

Wood and others 1995). In fact, mule deer use on big

sagebrush can be so heavy that extensive damage and

death to the big sagebrush plants can occur (Gysel

1960; McArthur and others 1988; Smith 1949; Wambolt

1996; Wambolt and Sherwood 1999). McArthur and

others (1988) reported 11 times more death on browsed

plants than nonbrowsed plants (fig. 2.13). Julander

(1937) ranked big sagebrush palatability to mule deer

in the top third of 148 plants. He ranked 99 plants

species less palatable than big sagebrush, 10 plant

species as the same, and 39 plants species as having

greater palatability than big sagebrush. What then is

the value of big sagebrush to mule deer?

Dietz and Yeager (1959, p. 151) pose two questions

in their attempt to assess the role of sagebrush in the

Table 2.7—Amount of big sagebrush (Artemisia tridentata) in

the diet of pronghorn (Antilocapra americana).

Season Big sagebrush Reference

Percent

Spring 18–35 Smith and Beale 1980

Summer 2–10 Smith and Beale 1980

Winter 55 Smith and Beale 1980

Cafeteria 63 Smith and Beale 1980

Spring 76 Ngugi and others 1992a

Spring 91 Ngugi and others 1992b

Spring 41 Hall 1963

Summer 36 Hall 1963

Winter 95 Hall 1963

Summer 12 Gates and Eng 1983

Fall 96 Gates and Eng 1983

Spring 37 McInnis and Vavra 1987

Summer 15 McInnis and Vavra 1987

Fall 55 McInnis and Vavra 1987

Winter 57 McInnis and Vavra 1987

Spring 41 Ferrel and Leach 1950

Summer 35 Ferrel and Leach 1950

Spring 95 Olsen and Hansen 1977

Summer 42 Olsen and Hansen 1977

Fall 77 Olsen and Hansen 1977

Winter 95 Olsen and Hansen 1977

Spring 30 Bayless 1969

Winter 51 Bayless 1969

Spring 6–85 Smith and Malechek 1974

Summer 0–5 Smith and Malechek 1974

Spring 41 Ferrel and Leach 1952

Fall 35 Ferrel and Leach 1952

Winter 95 Ferrel and Leach 1952

Summer 27 Johnson 1979c

Winter 65 Johnson 1979c

Fall 51 Couey 1946d

Winter 49 Singer and Renkin 1995

Yearly 28 Einarsen 1948

60-90 Marshall 1985

a

Mountain big sagebrush community.

b

Wyoming big sagebrush community.

c

Percent not by volume but by relative densities of plant fragments

in feces. d

Did not distinguish between big sagebrush (Artemisia tridentata)

and silver sagebrush (A. cana).

management of mule deer winter range (see Urness

1986): “Is sagebrush, specifically big sagebrush, an

important mule deer feed? Do deer feed on sage by

preference or through necessity?”

The answer to the first question is yes. Reynolds

(1960) referred to big sagebrush, along with five other

shrub species, as one of the staples in the diet of Utah

mule deer. In the State of Oregon, big sagebrush is

considered the main source of food for mule deer

(Mace 1957). For California, Longhurst and others

(1952, p. 41) stated: “The other group includes abundant species of inferior palatability, such as big sage
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 67

Figure 2.11—Mule deer feeding on big sagebrush (photo by Bruce L. Welch).

Figure 2.12—Big sagebrush providing cover for mule deer fawns

(photo by Thomas M. Holland).

Figure 2.13—Fenceline contrast where heavy mule

deer browsing killed mountain big sagebrush plants

(photo by E. Durant McArthur).
68 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

(Artemisia tridentata) and California juniper

(Juniperus californica). Despite the fact that these

may be ‘second choice’ foods, they furnish a large part

of the diet of deer in eastern California.” Studying the

food habits of mule deer in Wyoming, Goodwin (1975,

p. 1) concluded that “the most important diet species

were big sagebrush, antelope bitterbrush, and true

mountain mahogany.” A Nevada food habit study

conducted by Papez (1976) found that big sagebrush

and mountain mahogany were the most preferred

species on mule deer winter range (see Lesperance and

others 1970). Studying the preference and digestibility of big sagebrush and black sagebrush, Wambolt

and others (1987), Personius and others (1987),

Wambolt (1996), and Wambolt and Sherwood (1999)

found that big sagebrush is an important component

in the diet of mule deer. In their summary publication

of 99 studies concerning the foods of the Rocky Mountain mule deer, Kufeld and others (1973) reported

heavy use of big sagebrush in winter and spring with

moderate use in fall and light use in the summer.

Heavy use was defined as 20 percent or more in the

diet; moderate—between 5 and less than 20 percent;

and light—between 1 and less than 5 percent. Singer

and Renkin (1995) suggest that the 66 percent decline

in mule deer of the Northern Yellowstone Winter

Range may be due to declining Wyoming big sagebrush stands. Thus, it appears that the use of big

sagebrush by mule deer is a widespread phenomenon

throughout the Western United States.

In general, use peaks in the winter, with less use

occurring in the fall and spring and least in the summer

(table 2.8). Scanning the data given in table 2.8 shows

that the variation from one study to another is impressive. One possible explanation for such variability is

the amount of differential preference that mule deer

have for various subspecies and populations within

subspecies of big sagebrush (Hanks and others 1971;

Scholl and others 1977; Wambolt 1995, 1996; Welch

and McArthur 1981, 1986; Welch and others 1983). A

detailed discussion of wintering mule deer and other

animal species preference for subspecies and populations within subspecies of big sagebrush is given in

chapter V.

Do deer feed on sage by preference or through

necessity? Studying the food habits of the Great Basin

deer herds of California, Leach (1956) noted a switch

in the fall diet from bitterbrush to big sagebrush,

adding that light utilization of bitterbrush during

winter and spring was not necessarily due to lack of

bitterbrush. From his report (p. 279): “Had a March

sample of deer been collected, it might have revealed

a possible low utilization of bitterbrush, as in April.

This was found to occur on all the other deer ranges

reported in the study and could not always be attributed to the unavailability of bitterbrush forage.” Lassen

and others (1952, p. 217) also noted a winter shift from

bitterbrush to big sagebrush even when bitterbrush

was still available and further observed that “bitterbrush seems to have a period of low palatability in

February, March and April.” Welch and Andrus (1977,

p. 4), studying the use and value of rose hips for

wintering mule deer, observed: “Vasey big sagebrush

showed signs of being heavily browsed by deer. It was

clear that deer preferred rose hips and sagebrush as

browse. Black chokecherry and antelope bitterbrush

were not heavily browsed for another month.” As the

senior author of that report, I had expected or believed,

based on my knowledge of untested remarks in the

older literature, that big sagebrush was a food of last

resort. I was surprised that, in spite of the large

amount of available bitterbrush, the deer chose to eat

rose hips and big sagebrush. I made similar observations, during the winter of 1997 to 1998 (an open

winter), in shrubs gardens planted at the Point of the

Mountain south of Salt Lake City, UT. In those gardens wintering deer ate rose hips and big sagebrush

before feeding on bitterbrush and other shrub species.

During open winters, I have noted heavy utilization of

big sagebrush at Gordon Creek (near Helper, UT),

Hobble Creek (near Springville, UT), Ironton Mountain (near Provo, UT), White River (near Meeker, CO),

and Piceance Basin of Colorado. In addition, Welch

and Wagstaff (1992), who compared by paired plants

‘Hobble Creek’ mountain big sagebrush to bitterbrush

as a winter forage for mule deer, found that wintering

mule deer preferred ‘Hobble Creek’ mountain big sagebrush over bitterbrush.

After reviewing the literature, Peterson (1984, p. 75)

of the Montana Fish, Wildlife, and Park Department

stated:

In summary, the literature clearly provides a basis of

fact that sagebrush is a nutritional, digestible, and

desirable forage source for mule deer as well as for other

wild ungulates. The premise that sagebrush is detrimental to deer if it makes up the majority of that

animal’s diet is unfounded. Animal condition (fat reserves) upon entering the winter season are a critical

factor in determining overwinter survival. However,

winter ranges with forage plants high in nutritional

quality that will maintain animals or lessen the drain

on their fat reserves are important. Big sagebrush,

being a common component of many of our winter

ranges, has been shown to be capable of providing this

important winter sustenance.

The nutritive values of big sagebrush are discussed in

chapter IV.

Elk—Elk (Cervus canadensis) is a facultative associate of big sagebrush, which provides food and cover

during calving, and cover for fawns and adults (Booth

1947; Hansen and Clark 1977; Hansen and Reid 1975;

Johnson 1951; Kufeld 1973; Peterson 1995; Reid 1942;

Smith 1960; Wambolt 1995, 1996, 1998; Wambolt and

McNeal 1987). Wambolt (1998) found that elk wintering

on the Northern Yellowstone Winter Range preferred

habitats dominated by big sagebrush (fig. 2.14) and
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 69

Table 2.8—Percent of big sagebrush (Artemisia tridentata) in the diet of mule deer

(Odocoileus hemionus).

Spring Summer Fall Winter References

- - - - - - - - - - - - - Percent - - - - - - - - - - - - - -

4–64 Trace 0–10 12–81 Leach 1956a

52 Wambolt 1995b

40–49 Papez 1976c

34–44 4-12 27–65 Bissell and Strong 1955c

8–40 0–9 1 12–69 Tueller 1979d

16 MacCracken and Hansen 1981b

18 Lucich and Hansen 1981b

.1–13 13–37 Willms and McLean 1978e

4 4 Kasworm and others 1984b

26 Willms and others 1979

3 Hubbard and Hansen 1976b

3–21 Hansen and Dearden 1975b

46 23 44 Hansen and Reid 1975b

2–33 Carpenter and others 1979e

19 Hall 1963

4–45 Julander 1952c

12 7 17 40 Richens 1967e

7–43 Trace-17 39–70 Lassen and others 1952b

52 Wambolt 1996b

3–14 3 8–53 Urness 1986

0–8 64 Smith and Julander 1953

18–28 23 28 20–33 Goodwin 1975b

16 1 6 25 Wilkins 1957c

27–56 Hilken and Vavra 1981b

3 3 8–53 Austin and Urness 1983e

48 15 2–5 16–25 Rosenstock and others 1989b

0 Trace-63 Julander 1955

25 Austin and others 1983e

37 Smith 1952

23 Singer and Renkin 1995

26 0 15 37–51 Mustard 1958

41 Hansen and others 1977

10–63 Riggs and others 1990

3 0 1–39 Pederson and Welch 1982

0–64 0–23 0–45 Trace-81 All studies

a

Percentage of big sagebrush in the diet based on rumen volume; study conducted on four deer

herds and for 8 years. b

Percentage of big sagebrush in the diet was determined by fecal microhistological techniques.

c

Percentage of big sagebrush in the diet was determined by rumen volume.

d

Percentage of big sagebrush in the diet was determined by rumen volume; study conducted on

six deer herds and for 9 years. e

Percentage of big sagebrush in the diet was determined by percent of bites.

Figure 2.14—Big sagebrush providing

feed for elk (photo by Carl L. Wambolt).
70 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Figure 2.15—Elk, 7 in all, using big sagebrush as

cover (photo by Carl L. Wambolt).

that excessive consumption of big sagebrush has caused

big sagebrush stands to decline. He reported that

mean big sagebrush canopy cover inside 36- and 41-

year old elk exclosures was 20 percent but only 7

percent outside. Even after 36 or 41 years, Wambolt

(1998) felt that big sagebrush recovery inside of the

exclosures is not complete. This concern about elk’s

excessive browsing on big sagebrush was voiced more

than 70 years ago but has been largely ignored even

today (Rush 1932; Wright and Thompson 1935).

The utilization of big sagebrush by elk may have a

nutritional basis (Wambolt and Sherwood 1999). During fall and winter, protein content of grasses does not

meet the protein requirement of elk; thus, Wambolt

and others (1997) reasoned that elk consumed big

sagebrush as a means of raising dietary protein (nutritive value of big sagebrush is discussed in chapter IV).

Kufeld (1973) ranked it as a valuable winter and fall

food (5 to 20 percent of the diet; Kufeld and others

1973). Murie (1951, p. 223) states:

Elk are fond of the matured seed stalks, which project

above the snow, and the animals have been seen going

from bush to bush, consistently picking them off. Although A. tridentata may be considered a valuable food

resource at a time when other sources fail, it should not

be relied on as an indicator of food shortage. The degree

of use is important in judging range depletion because

elk have been known to eat sagebrush leaves in fall and

early winter, at least as early as November 14, when

other forage was plentiful.

Big sagebrush is used as calving ground and cover

for calves (fig. 2.15). Johnson (1951) reported that 42

percent of newborn calves were found in big sagebrush, 33 percent in timber, and 25 percent on the edge

of big sagebrush and timber. However, 77 percent of

all calves were found in big sagebrush compared to 11

percent in timber and 4.5 percent on the edge of timber

and big sagebrush. Ward (1973) did not agree with the

findings of Johnson (1951). In his report, “Sagebrush

control with herbicide has little effect on elk calving

behavior,” he stated in the abstract that “elk did not

change their calving behavior or feeding habits on a

site where 96.7 percent of the big sagebrush (Artemisia tridentata) cover had been killed with 2 pounds

acid equivalent of 2,4-D herbicide.” Unfortunately, no

calving data were provided. His data showed that

spraying had no effects on feeding and presence of

calves and adults on the sprayed or unsprayed areas in

the summer.

Rocky Mountain Bighorn Sheep—The Rocky

Mountain bighorn sheep (Ovis canadensis) is another

facultative associate of big sagebrush. Studying the

winter food habits of two herds of Rocky Mountain

bighorn sheep, Keating and others (1985) reported

that 25 percent of the winter diet was big sagebrush,

which was the number one item in their diet. The

second herd’s diet was 6 percent big sagebrush, which

ranked fifth in their diet. Big sagebrush on the second

herd’s range was nil because of overuse by wintering

elk (Wambolt 1998). On winter ranges where big

sagebrush canopy cover was 0.5 and 0.2 percent,

Kasworm and others (1984) reported Rocky Mountain

bighorn sheep diets contained 1.9 to 2.3 percent big

sagebrush with deer and elk, on the same sites, also

consuming big sagebrush. Martin and others (1951)

ranked big sagebrush high as a winter food for Rocky

Mountain bighorn sheep.

Desert Bighorn—The desert bighorn (Ovis

canadensis nelsoni) is another facultative associate of

big sagebrush and uses big sagebrush, in a limited

way, as a forage plant (Barrett 1964; Bradley 1965;

Browning and Monson 1981; Dunnaway 1972;

McQuivey 1978; Yoakum 1964, 1966). Amount of big

sagebrush in the diet of desert bighorns varied from 0

to 24 percent (Barrett 1964; Bradley 1965; Dunnaway

1972; Yoakum 1964, 1966). McQuivey (1978) and

Browning and Monson (1981) listed big sagebrush on

certain sites among the most preferred shrubs. There

was no mention of big sagebrush cover value in the

habitats of desert bighorn.

Domestic Sheep—The use of big sagebrush by

domestic sheep has been known for a long time. Concerning domestic sheep, Nelson (1898, p. 25) stated:

The amount of sagebrush consumed in the desert is

simply amazing. Sheepmen and herdmen say that for

sheep a straight sagebrush diet at certain times seems

to ‘meet a long felt want.’ Whole bands will leave all

other forage and browse sagebrush for a day or two at

a time, after which they will not touch it again for some

days, or even weeks. This is especially true for the

common sagebrush (Artemisia tridentata Nutt.).

Studying sheep utilization of big sagebrush accessions, Welch and others (1987) reported that wintering
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 71

sheep consumed big sagebrush, despite the fact the

sheep had continuous access to high quality alfalfa hay

and 0.28 kg of rolled barley per head per day. Also,

Burritt and others (2000, p. 91), studying the influence

of early life experiences and macronutrients on the

intake of mountain big sagebrush by sheep found:

“when sagebrush comprised 20 percent of an alfalfa/

barley ration, lambs ate the sagebrush ration readily

even when a nutritious alternative was offered indicating the flavor of sagebrush did not prevent lambs from

feeding.”

Sampson (1924), using the term “black sage” for

big sagebrush, described big sagebrush as not as

palatable as some of the other sagebrushes but is

relied upon as a “filler” for cattle, sheep, and goats on

winter and autumn range. He pointed out that big

sagebrush can be a straight ration for sheep on winter

range when more palatable low-growing forage is

covered with snow. On small experimental paddocks

of crested wheatgrass used for tests of lambing, Springfield (1960) reported heavily utilization (80 percent) of

big sagebrush by pregnant ewes in early May. Snowder

and others (2001), studying the diet of free-grazing

Rambouillet sheep in Idaho, found that mountain big

sagebrush comprised 22 percent of the September diet

and 32 percent of the October diet. Research conducted by Frischknecht and Harris (1973) suggests,

due to the amount of big sagebrush eaten by sheep,

that sheep could be used as a biological control agent

to control big sagebrush in crested wheatgrass

plantings. Their data showed that fall grazing by

sheep decreased the size of big sagebrush plants and

greatly reduced the production of flower stalks, thus

lowering the number of seeds available for establishing more plants in the seedling.

General Comments—Hoffman and Wambolt

(1996) reported that reductions in seed and vegetative

production of big sagebrush plants in Yellowstone

National Park was due to excessive browsing by elk in

large numbers. The reduction of inflorescences due to

excessive browsing is a morphological problem and not

an energy or carbon assimilation problem (Evans and

Black 1993; Rodriguez and Welch 1989). Inflorescences arise from axils of the leaves of the vegetative

shoots. Therefore, browsing removes the primordial

cells that give rise to inflorescences (Diettert 1938).

High populations of mule deer can, also, damage big

sagebrush stands (McArthur and others 1988;

Rodriguez and Welch 1989; Smith 1949; Wambolt

1998; Wambolt and Sherwood 1999).

K. Johnson (1977) observed:

The sheer abundance of big sagebrush makes it difficult

to overestimate its importance. It provides high-quality food for both livestock and wildlife, although the

volatile oils tend to make it unpalatable and may

interfere with digestion and nutrition [see chapter IV

for a detail discussion of volatile oils, digestion, and

palatability]. The volatile oils vary with subspecies,

areas, seasons and sometimes individual plants. But

for general Wyoming conditions, big sagebrush, particularly a dwarf form, provides important winter forage for sheep, antelope and deer, especially as part of a

mixed diet.

The larger growth forms provide protective cover, a

ready source of fuel, and a landscaping ornamental.

There has been wide use of the plant in folk medicine as

a tonic, antiseptic and tea. Where big sagebrush attains

undesirable concentrations, it may be readily controlled

by fire and irrigation, or by mechanical and herbicidal

treatments, to increase forage production [these items

are covered in chapter VII]. Conversely, it can be very

useful in restoring depleted big game range. So in the

overall view, big sagebrush may be said to be an

extremely hard working, if unglamorous, pillar of the

plant community—sometimes loved, sometimes hated,

always important.

Reptiles

Unlike mammals and birds, reptiles do not have a

species that is known to have an obligate relationship

with big sagebrush—all are facultative associates of

big sagebrush. A list is given in table 2.9.

Even though many of these species can be found in

vegetative types other than big sagebrush, their populations may be higher in big sagebrush habitats than

other vegetative types. Diller and Wallace (1996), for

example, reported capturing more western rattlesnakes

(Crotalus viridis) and gopher snakes (Pituophis

melanoleucus) in big sagebrush communities than in

winterfat (Ceratoides lanata), shadscale (Atriplex

confertifolia), greasewood, and grassland communities. Studying the response of native vertebrate populations to crested wheatgrass plantings, Reynolds and

Trost (1980b) (also see Reynolds 1979a) noted greater

numbers of short-horned lizards (Phrynosoma

douglassii), sagebrush lizards (Sceloporus graciosus),

and gopher snakes in big sagebrush than in crested

wheatgrass plantings.

The importance of big sagebrush in the lives of birds,

mammals, and reptiles is masterfully illustrated by a

study conducted by Reynolds and Trost (1980a, p.

666). Their conclusion was simple and to the point:

“Converting native sagebrush rangeland to a crested

wheatgrass monoculture has a negative effect on native wildlife populations.”
72 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 2.9—Reptiles and amphibians having a facultative association with big

sagebrush (Anderson and others 1987; Baxter and Stone 1980; Cox

and Tanner 1995; Grinnell and others 1930; Hammerson 1982; Linder

and Fichter 1977; McEwen and DeWeese 1987; Merriam and Stejneger

1891; Nussbaum and others 1983; St. John 1980; Tanner 1999; West

1983a,b; Young and Evans 1980). Common and scientific names are

given as listed in the various cited articles; some repetition.

 Common names Scientific name

Brown-shouldered uta Uta stansburiana stansburiana

Bullsnake Pituophis melanoleucus

 Pituophis catenifer

Collared lizard Crotaphytus collaris baileyi

Desert horned lizard (horned toad) Phrynosoma platyrhinos

Desert night snake Hypsiglena torquata deserticola

Desert spiny lizard Sceloporus magister

Desert striped whipsnake Masticophis taeniatus

Eastern short-horned lizard Phrynosoma douglassi brevirostre

Gopher snake Pituophis melanoleucus

 Pituophis catenifer deserticola

Great Basin gopher snake Pituophis melanoleucus deserticola

Great Basin skink Eumeces skilitonianus utahensis

Great Basin spadefoot toad Scaphiopus intermontanus

Great Basin rattlesnake Crotalus viridis lutosus

Great Basin whiptail Cnemidophorus tigris

Leopard lizard Crotaphytus wislizeni

Longnose leopard lizard Gambelia wislizenii

Long-nosed snake Rhinocheilus lecontei

Long-toed salamander Ambystoma macrodactylum

Many-lined skink Eumeces multivirgatus

Mesa Verde night snake Hypsiglena torquata loreala

Midget faded rattlesnake Crotalus viridis concolor

Milk snake Lampropeltis triangulum

Mormon racer

New Mexico spadefoot Scaphiopus multiplicatus

Night snake Hypsiglena torquata

Northern alligator lizard Gerrhonotus coeruleus

Northern plateau lizard Sceloporus undulatus elongatus

Northern sagebrush lizard Sceloporus graciosus graciosusa

Northern tree lizard Urosaurus ornata wrighti

Pacific blue-bellied lizard Sceloporus occidentalis occidentalis

Pale milk snake Lampropeltis triangulum

Plains spadefoot toad Scaphiopus bombifrons

Plateau striped whiptail Cnemidophorus velox

Prairie rattlesnake Crotalus viridis

Pygmy horned lizard Phrynosoma douglassi douglassi

Racer Coluber constrictor

Red racer Masticophis flagellum piceus

Sagebrush lizard Sceloporus graciosusa

Side-blotched lizard Uta stansburiana

Short-horned lizard Phrynosoma douglassi

Striped racer Coluber taeniatus taeniatus

Striped whipsnake Masticophis taeniatus

Tiger salamander Ambystoma tigrinum

Tree lizard Urosaurus ornatus

Wandering garter snake Thamnophis elegans vagrans

Western blackhead snake Tantilla planiceps

Western fence lizard Sceloporus occidentalis

Western longnose snake Rhinocheilus lecontei lecontei

Western rattlesnake (rattlesnake) Crotalus viridis

 Crotalus lucifer

Western spadefoot toad Scaphiopus hammondii

Western skink Eumeces skiltonianus

(con.)
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 73

Western terrestrial garter snake Thamnophis elegans

Western toad Bufo boreas

Western whiptail Cnemidophorus tigris

Western yellow-bellied racer Coluber constrictor mormon

Whip-tail lizard Cnemidophorus tessellatus tessellatus

Woodhouse’s toad Bufo woodhousei

Yellow-bellied racer Coluber constrictor

a

McEwen and DeWeese (1987) lists the sagebrush lizard as a possible obligate of big

sagebrush.

Table 2.9 (Con.)

 Common names Scientific name

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Notes

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Chapter

III

Other Foragers and

Winter Damage on Big

Sagebrush

This chapter describes organisms that, although they receive little attention, feed on

big sagebrush or consume organisms that feed on big sagebrush. The fungi (diseases),

insects, spiders, scorpions, lichens, and parasitic plants that live in, on, and around big

sagebrush plants are discussed. Some have obligate relationships with big sagebrush,

others a facultative relationship. Obligate associations are those associations necessary

for the organism to complete its life cycle. Facultative associations vary from associating

with big sagebrush 80 percent of the time to infrequent use of big sagebrush, perhaps

20 percent of the time. Also included is a section dealing with nonparasitic diseases of

big sagebrush.

Diseases of Big Sagebrush _________________________________________

A diseased big sagebrush plant is a plant having a parasitic or nonparasitic condition

that interferes with normal development. Parasitic agents of plant disease are called

pathogens and include bacteria, fungi, nematodes, viruses, mycoplasmas, viroids, and

parasitic plants. Three factors, known as the “disease triangle,” must be present for a

parasitic disease to develop: a susceptible host (in this case, the big sagebrush plant),

a pathogen (a rust fungus), and proper environment (free water, correct temperature,

and so forth).

Nonparasitic agents of plant disease are nonliving agents in the environment such as

unfavorable water relationships (lack or excess), mineral deficiencies, mineral excesses,

toxic substances in the soil or atmosphere, low or high temperatures, or mechanical

damage that prevent the normal development of a plant.

Nonparasitic Diseases

Extensive winter injury of mountain big sagebrush (Artemisia tridentata ssp.vaseyana,

see chapter I for a discussion on subspecies of big sagebrush) occurred in the Western

United States during the winter of 1976 to1977 (Nelson and Tiernan 1983). Winter

injury can result from either an unusual temperature event or winter drought. In the

case of an unusual temperature event, an unusual cold wave, usually in the fall and prior

to dormancy, can result in freeze injury to plants. An unusual warm spell, usually in late
82 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

winter, which will stimulate growth activity, followed

with a return to winter cold, can result in freeze injury.

Winter drought can cause lethal dehydration of plant

tissues resulting from continued transpiration and

inadequate water absorption by the root system. Abnormally low snow depth may allow the soil and root

systems to freeze, thus preventing the replacement of

water loss in the aboveground plant parts. Also, a lack

of insulating snow cover, accompanied with severe

cold temperatures and drying winds, can cause water

loss through freeze drying or sublimation.

Most of the winter injury that occurred during the

winter of 1976 to1977 in Idaho, Utah, Nevada, Wyoming, and Colorado was above 6,000 feet (1,800 m);

however, damage to mountain big sagebrush was

reported from California and Oregon at elevations

below 6,000 feet. Nelson and Tiernan (1983, p. 3)

stated: “Virtually all large plants of mountain big

sagebrush were killed on the high plateau areas we

surveyed on Idaho’s Sawtooth National Forest and Utah’s

Uinta and Manti-LaSal National Forests [fig. 3.1]. Even

in the most severe kill areas, however, some young

plants up to 12 inches (30 cm) high were not affected.”

Hanson and others (1982) and Nelson and Tiernan

(1983) observed that partial killing of mature plants

was common and that the most severe killing of

mountain big sagebrush took place in areas normally

having the deepest covering of snow, but killing was

less or even lacking in areas that normally have thinner

snow cover. Hanson and others (1982, p. 145) observed:

Mountain big sagebrush plants that are not normally

covered by snow seem to have evolved a dormancy

condition that enables them to withstand winterinduced physiologic droughts. However, mountain big

sagebrush plants that have evolved in an environment

where snow cover normally prevents the soils from

freezing and provides a protective plant cover that

reduces transpiration demand are apparently not acclimated to long periods of winter-induced physiologic

drought.

Nelson and Tiernan (1983) found that winter injury

on mountain big sagebrush occurred in the following

Western States: California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, and Wyoming. They

and Hanson and others (1982) described the probable

cause of the widespread winter injury to mountain

big sagebrush as either freezing or winter desiccation

or both. During the November through February

period, precipitation was extremely low, about 31

percent of normal, resulting in thin snow cover. Likely,

soils were frozen and soil moisture unusually low.

November’s above-normal temperatures and

December’s below-normal temperature could have

resulted in mountain big sagebrush tissues being

susceptible to damage by freezing. Walser and others

(1990) showed that properly hardened-off big sagebrush short shoots and stems can tolerate temperatures as low as –50°C; however, subject to 6 days of

warm temperatures (20°C), these same plants would

freeze kill at –20 °C. February’s above-normal temperatures may have broken winter dormancy, resulting in an increased in the transpiration rate during a

Figure 3.1—Extensive mountain big sagebrush mortality on the high Cassia Plateau of southern Idaho,

Sawtooth National Forest (photo by David L. Nelson).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 83

period of low soil moisture, or frozen soil. Either could

cause lethal desiccation of aboveground parts. In March

the temperatures fell below normal and again could

have, for the second time, caused freezing damage to

the mountain big sagebrush plants.

Nelson and Tiernan (1983, p.15) stated: “The extensive kill of big sagebrush over large areas represents a

significant natural vegetational change. These areas

will eventually return to [mountain big] sagebrush,

however, because some young plants survived and

seeding will occur from plants in surrounding areas.”

Parasitic Diseases

In 1973, Sturges and Nelson (1986) discovered a

snowmold disease caused by a fungus on mountain big

sagebrush in south-central Wyoming (fig. 3.2 and 3.3).

This disease has caused extensive death in areas of

heavy snowpacks in Colorado, Utah, and Wyoming

(fig. 3.2). This disease is just the opposite from the

winter injury just described. Winter injury is caused

by the lack of snow cover; with snowmold the cause is

too much snow. This unknown snowmold fungus was

Figure 3.2—Big sagebrush plants partially and some entirely killed by a snowmold fungus (photo by David L. Nelson).

Figure 3.3—A dense, web-like mycelium covers the

snowmold infected portion of a big sagebrush plant after

snowmelt (photo by David L. Nelson).
84 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

not found on Wyoming big sagebrush (A. t. ssp.

wyomingensis) or black sagebrush (A. nova), taxa that

occupy sites with typically little snow cover.

Can the occurrence of snowmold be related to snow

depth and not to genetic differences among the two

subspecies and black sagebrush? Yes, as Sturges and

Nelson (1986) found in their study that when the snow

cover was less than 16 inches, snowmold infected 2

percent of the plants, but when snow cover exceeded

47 inches, percentage of infected plants increased to

93 percent. This disease reduces the canopy cover or

kills mountain big sagebrush plants in areas of deeper

snow accumulation.

In another study, Nelson and Sturges (1986) were

able to infect, under laboratory conditions, plants of

basin big sagebrush (A. tridentata ssp. tridentata),

Wyoming big sagebrush, and black sagebrush with

the snowmold fungus, giving more proof that snow

depth is more important than genetic makeup of the

host sagebrush (fig. 3.4). Morphology, ultrastructure,

and etiology of the snowmold fungus is given in Hess

and others (1985) and Nelson and Sturges (1986).

Five rust fungi have been reported to induce rust

diseases on big sagebrush: Puccinia atrofusca, P. cnicioleracei, P. similis, P. tanaceti, and Uromyces

oblongisporus (Arthur and Cummins 1962; Cooke and

Shaw 1952; Cummins 1975; Weber and others 2001;

Welch and Nelson 1995). The most studied of these

has been black stem rust caused by Puccinia tanaceti

(Welch and Nelson 1995). This disease is referred to as

“black stem rust” because of the conspicuous and

characteristic “blackening” of infloresecent stems resulting from dense sporulation of the black telial sori

(fruiting structures) (fig. 3.5). Arthur and Cummins

(1962) noted that this rust fungus occurs on 35 species

Figure 3.4—Sagebrush plants infected with

snowmold under laboratory conditions. Plant on left

not inoculated (photo by David L. Nelson).

Figure 3.5—Nature of the black stem rust on big sagebrush. The black circular structures are the telial sori of

the rust fungus; magnification 10x (photo by David L.

Nelson).

of Artemisia in North America. On big sagebrush, P.

tanaceti has been collected in all 11 conterminous

Western States except Arizona. It is an autoecious

obligate parasite; that is, all spore stages (pycnial,

aecial, uredinial, telial) occur on one host. Usually,

infection levels of this disease are low and require

some hand searching through vegetative and inflorescent shoots to locate the widely scattered telial sori,

but occasionally (perhaps 1 out of 10 or 15 years),

heavy infections build to the point where signs (coalescing of individual telial sori together into large

black bodies) of the disease can be seen 2 or 3 feet away

from an infected big sagebrush plant (fig. 3.6).

With heavy infection, during mid to late summer,

Welch and Nelson (1995) observed, in a seed increase

garden of ‘Hobble Creek’ mountain big sagebrush

(Welch and others 1986), that both ephemeral and
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 85

persistent leaves had begun to defoliate. Defoliation

became severe, especially on vegetative shoots, and

continued through fall and winter. There was a noticeable stunting of inflorescent shoots and an inhibition

of floret development. Only a few of the late-forming

florets on the tip of inflorescent shoots eventually

flowered. A comparison among inflorescent shoots,

with different levels of infection, is illustrated in figure

3.6. At heavy infection levels, seed production was

reduced by 63 to 91 percent (Welch and Nelson 1995).

Decreased photosynthetic capacity of plants by defoliation, stunting of inflorescent shoots, and inhibition

of floret development is likely the main cause of reduced seed productivity.

Figure 3.6—Illustration of different fungus infection intensity. Inflorescent shoots (left to right)

with corresponding enlargement below showing intensity level of telial sori on leaves, stems,

and florets. (One-third actual size of inflorescent shoots, 2x magnification of telial sori, photos

by David L. Nelson.)

Nelson and Krebill (1981) described a big sagebrush

wilt disease occurring in uniform shrub testing gardens (fig. 3.7). The pathogen or pathogens of this

disease have not been identified. Nelson and Krebill

(1981, p. 185) described the disease development:

“First symptoms of the disease usually occurred in late

fall or early spring as wilted leaves and shoot tips. By

midsummer, portions or entire plants collapsed and

died.” They noted that a prominent bluish green vascular discoloration was associated with some but not

all dying plants and sometimes with nonwilted

plants. This discoloration can be symptomatic of the

Verticillium-induced disease of woody plants. Nelson

and Krebill (1981, p. 185) further observed that
86 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Figure 3.7—Wilt disease symptoms on big sagebrush plant growing on a uniform shrub testing

garden. Note wilted leaves and shoots tips (photo by

David L. Nelson).

Table 3.1—Pathogenic and nonpathogenic fungi collected from big sagebrush (Weber and

others 2001).

Alternaria tenuis

Camarosporium compositarum

Cucurbitaria obducens

Diplodina tridentatae

Discomycete sp.

Epicoccum nigrum

Fusarium sp.

Glyphium corrugatum

Godronia montanensis

Guepiniopsis buccina

Guepiniopsis torta

Heliocybe sulcata

Heterobasidion annosum

Leptosphaeria artemisiae

Leptosphaeria preandina

Leptosphaeria tumefaciens

Odontotrema oregonense

Phoma terrestris

Phyllosticta raui

Puccinia absinthii

Puccinia atrofusca

Puccinia cnici-oleracei

Puccinia similis

Puccinia tanaceti

Pyrenopeziza artemisiae

Stigmina sycina

Syncarpella tumefaciens

Teichospora obducens

Teichospora sp.

Typhula sp.

Uromyces oblongisporus

“portions of the root systems of some wilt-diseased

plants were necrotic, but death of plants did not seem

to be associated with earlier advanced root rot or

decay.” For portions of dead crown, they found that the

corresponding portion of the root system was also

dead.

Fungi—Weber and others (2001) have compiled a

list of pathogenic and nonpathogenic fungi species, 31

in all, that have been collected from big sagebrush

(table 3.1).

Insects and Other Arthropods of Big

Sagebrush _____________________

Even for the casual observer of big sagebrush, the

number of insects and other arthropods associated

with this species of plant is impressive and truly

deserves the name “mother sage.” Many insects feed

directly on big sagebrush, and some feed on the insects

that feed on the plant. The story of the insects and

other arthropods of big sagebrush is a fascinating

lesson in ecosystem association.

Aphids and Other Parasites

Aphids are a large group of soft bodied insects

somewhat pear-shaped, 3⁄

16 to 5

⁄

16 of an inch long, with

a pair of cornicles (tubes or small “horns”) near the

posterior end of the abdomen (fig. 3.8). When at rest,

wings when present are held horizontal (Borror and

White 1970). Aphids are usually found in large numbers feeding on stems, leaves, and inflorescences and

may cause curling or wilting of the plant. Some are

vectors of plant diseases (Borror and White 1970).

Their life cycle is complex, involving bisexual and

parthenogenetic (without fertilization) generations,

winged and wingless forms, and with some species

alternating food plants sometime during their life

cycle. Aphids overwinter as eggs, which in the spring

hatch as wingless females that give rise to still more

wingless females. After two or more generations,

winged females are produced that usually migrate to

a different food plant. In turn, these winged migrant

females reproduce parthenogenetically wingless females, and later winged females are again produced

that migrate back to the original food plant to produce

a generation of males and females that mate, and the

females lay overwintering eggs (Borror and White

1970).

Some species of ants form close associations with

aphids. They collect aphid eggs and overwinter them

in their nests, later transporting the eggs to feed

plants in the spring where the ants care and tend the
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 87

Table 3.2—Species of aphids collected from

big sagebrush (Artemisia tridentata)

(Gillette and Palmer 1928, 1933;

Knowlton 1983).

Anuraphis hermistonii

Anuraphis oregonensis

Aphis artemisicola

Capitophorus heterohirsutus

Epameibaphis atricornis

Epameibaphis frigidae

Epameibaphis utahensis

Flabellomicrosiphum knowltoni

Flabellomicrosiphum tridentatae

Hyperomyzus accidentalist

Macrosiphoniella frigidicola

Macrosiphum longipes

Microsiphoniella acophorum

Microsiphoniella artemisiae

Microsiphoniella oregonensis

Obtusicauda albicornus

Obtusicauda anomella

Obtusicauda artemisicola

Obtusicauda artemisiphila

Obtusicauda cefsmithi

Obtusicauda coweni

Obtusicauda essigi

Obtusicauda filifoliae

Obtusicauda flavila

Obtusicauda frigidae

Obtusicauda jonesi

Obtusicauda zerohypsi

Obtusicauda zerothermum

Pleotrichophorus decampus

Pleotrichophorus glandulosa

Pleotrichophorus heterohirsutus

Pleotrichophorus infrequens

Pleotrichophorus longipes

Pleotrichophorus pseudoglandulosus

Pleotrichophorus pullus

Pleotrichophorus quadritrichus

Pleotrichophorus quadritrichus ssp. pallidus

Pleotrichophorus spatulavillus

Pleotrichophorus wasatchii

Pleotrichophorus zoomontonus

Pseudoepameibaphis essigi

Pseudoepameibaphis glauca

Pseudoepameibaphis tridentatae

Pseudoepameibaphis xenotrichis

Pseudoepameibaphis zavillus

Zyxaphis canae

Zyxaphis filifoliae

Zyxaphis hermistonii

Zyxaphis infrequens

Zyxaphis minutissima

Zyxaphis oregonensis

Zyxaphis utahensis

Figure 3.8—A potpourri of aphids feeding on big

sagebrush (photos by Bruce L. Welch).

aphid during the season and even transport aphids to

new feed plants. Ants will defend aphid pasture plants

on big sagebrush against defoliating insects (Arnott

1957).

Our knowledge of aphids and big sagebrush comes

mainly from the life work of George F. Knowlton.

Following is a list of his publications concerning species of aphids collected on big sagebrush: Knowlton

(1929a,b, 1935a,b, 1946a,b, 1947, 1948, 1983),

Knowlton and Allen (1938, 1940); Knowlton and Smith

(1936a,b,c, 1937).

Knowlton’s (1983) summary publication on the

aphids of Utah notes there are more than 550 species

in the State of which 47 were collected from big

sagebrush, making it the host champion out of 259

plant species listed (table 3.2). Mean number of aphid

species per plant species was three. Rubber rabbitbrush (Chrysothamnus nauseosus) was second with 22

species. Knowlton (1983, p. 2) observed: “Some plants,
88 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

such as the common sagebrush (Artemisia spp.) host a

great number of aphid species, nearly all of which feed

only on this genus of plants.” Gillette and Palmer

(1928, 1933) describe five more species of aphids collected from big sagebrush not included in the Knowlton

(1983) report, bringing the total to 52 (table 3.2).

Messina and others (1996) used two species of aphids

(Obtusicauda coweni and O. filifoliae), as well as other

insect species, to evaluate four genetic hypotheses

concerning herbivore attack (preference or palatability) on hybrids and parental lines between two subspecies of big sagebrush, basin and mountain. The four

hypotheses were: dominance, additivity, elevated hybrid susceptibility (that is, the degree of feeding on the

plant—the higher the feeding the greater the susceptibility), and elevated hybrid resistance. The test was

to compare the responses of the insects to the parents

and hybrids, and by inference, which of the four

hypotheses best explain the observations. O. filifoliae

did not discriminate among hosts or did not show

differential preference for parents or hybrids; however, O. coweni seem to like the basin big sagebrush

parent and the hybrid better than the mountain big

sagebrush. Messina and others (1996, p. 513) concluded: “Although we eliminated several confounding

factors, our results agree with the conclusion from

natural hybrid zones that insect responses to hybrid

plants are likely to be idiosyncratic; even congeneric

species did not respond similarly to hybrid and parental plants.” Thus, clarity is still lacking as to what

factors contribute to palatability or the lack thereof

(see chapter IV for details).

Pike and others (1997) conducted an extensive

survey across eastern Washington on big sagebrush

for parasitic Hymenoptera that parasitize the various species of aphids. All insects collected were members of the Braconidae family, a large and widely

distributed group whose larvae are parasites of a

great variety of insects including aphids on big sagebrush. From this survey, Pike and others (1997)

identified 10 species parasitizing a number of big

sagebrush aphid species just from the eastern Washington region (table 3.3).

Where big sagebrush is the keystone species, one

could describe the location as a miniecosystem. First,

there are the aphids feeding directly on big sagebrush

with 10 or more species of parasitic Hymenoptera

feeding on the aphids, and an unknown number of

ladybird beetle species (fig. 3.9) feeding on both aphids

and their parasites, plus an unknown number of ant

species pasturing their honeydew-producing “cows,”

aphids, on big sagebrush. All this is based on one plant

species and aphids that feed on it; this constitutes a

relatively rich diversity of life (52 species of aphids, 10

species of parasitic Hymenoptera, an unknown number of ladybird beetle species, and aphid-attending

ants).

Table 3.3—Parasitic Hymenoptera that parasitize aphids

feeding on big sagebrush (Artemisia tridentata)

(Pike and others 1997).

Parasitic Hymenoptera

Aphid parasitized

Binodoxys clydesmithi

Obtusicauda artemisicola

Obtusicauda coweni

Zyxaphis sp.

Binodoxys coruscanigrans

Obtusicauda coweni

Ephedrus californicus

Obtusicauda coweni

Obtusicauda sp.

Lysaphidus adelocarinus

Epameibaphis atricornis

Flabellomicrosiphum knowltoni

Flabellomicrosiphum tridentatae

Flabellomicrosiphum sp.

Microsiphoniella acophorum

Microsiphoniella sp.

Obtusicauda artemisicola

Obtusicauda filifoliae

Obtusicauda sp.

Pleotrichophorus sp.

Pseudoepameibaphis essigi

Pseudoepameibaphis glauca

Pseudoepameibaphis tridentatae

Zyxaphis sp.

Lysaphidus ramithyrus

Pleotrichophorus sp.

Zyxaphis sp.

Lysiphlebus utahensis

Obtusicauda artemisicola

Obtusicauda coweni

Obtusicauda filifoliae

Praon artemisaphis

Flabellomicrosiphum knowltoni

Obtusicauda coweni

Obtusicauda sp.

Pleotrichophorus sp.

Praon artemisicola

Epameibaphis atricornis

Flabellomicrosiphum knowltoni

Flabellomicrosiphum sp.

Obtusicauda filifoliae

Pleotrichophorus sp.

Pseudoepameibaphis tridentatae

Trioxys artemisiarum

Macrosiphoniella ludovicianae

Trioxys bonnevillensis

Epameibaphis atricornis

Epameibaphis sp.

Epameibaphis utahensis

Flabellomicrosiphum knowltoni

Flabellomicrosiphum tridentatae

Flabellomicrosiphum sp.

Microsiphoniella acophorum

Microsiphoniella sp.

Obtusicauda artemisiae

Obtusicauda artemisiphila

Obtusicauda filifoliae

Obtusicauda sp.

Pleotrichophorus sp.

Pseudoepameibaphis essigi

Pseudoepameibaphis tridentatae

Zyxaphis canae
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 89

Beetles

Beetles, which form the largest order of insects

(Coleoptera), feed on all sorts of plant and animal

materials (Borror and White 1970). At least 23 species

are known to be associated with big sagebrush, most of

which feed directly on this plant (table 3.4; fig. 3.10).

Barr and Penrose (1969) noted that two beetle species (Crossidius ater and Prionus (Homaesthesis) integer) were found in the roots of big sagebrush. Barr and

Penrose (1969, p. 92–93) observed of P. integer: “On

one occasion larvae were found damaging newly planted

bean seeds in a field near Burley, Cassia County, and

in another instance, cutting underground stems of

potato plants in a field near American Falls, Power

County. In both cases the fields had been recently

cleared for cultivation.” Tilden and Mansfield (1944)

found that the beetle Coenonycha bowlesi occurred

only on the tips of big sagebrush plants, and their

mating and feeding activities were strictly nocturnal.

Table 3.4—Beetles associated with big sagebrush (Artemisia tridentata)

(Banham 1962; Barr and Penrose

1969; Blake 1931; Furniss and

Barr 1975; Graham and others

2001; Halford and others 1973;

Massey and Pierce 1960; Pringle

1960; Rickard 1970; Rogers and

Rickard 1975; Tilden and

Mansfield 1944).

Calosoma luxatum

Coenonycha bowlesi

Coniontis setosa

Crossidius ater

Dichelonyx sp.

Eleodes hispilabris

Eleodes sp.

Eusattus muricatus

Exema conspersa

Lyctus sp.

Mecas bicallosa

Monoxia grisea

Monoxia sp.

Octinodes sp.

Pelecyphorus densicollis

Philolithus densicollis

Prionus (Homaesthesis) integer

Stenomorpha puncticollis

Sternechus sp.

Trirhabda attenuata

Trirhabda confusa

Trirhabda nitidicollis

Trirhabda pilosa Figure 3.9—Ladybird beetles hunting for aphids

and other insects on big sagebrush (photos by

Bruce L. Welch).

Figure 3.10—Beetles feeding on big sagebrush

(photos by Bruce L. Welch).
90 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

A survey of two species of darkling beetles (Philolithus

densicollis and Stenomorpha puncticollis) in big sagebrush and greasewood (Sarcobatus vermiculatus)

showed higher number of beetles in the big sagebrush

habitat than in the greasewood habitat (Rickard and

Havefield 1965; Rogers and Rickard 1975), although

greasewood contained higher numbers of Stenomorpha

puncticollis. The 1973 survey found fewer numbers of

the two beetles in both habitats compared to the 1963

survey.

The beetle species that has received the greatest

amount of study and attention is Trirhabda pilosa

because of its ability, during heavy infestations, to kill

big sagebrush (Anonymous 1956; Arnott 1957; Banham

1961; Furniss and Carolin 1977; Haws and others

1990; Pringle 1960). Haws and others (1990, p. 137)

noted that land managers often asked, “Where can I

get some of these bugs?” This species is an obligate

insect on big sagebrush (Anonymous 1956; Pringle

1960). Its life history has been described by a number

of workers (Anonymous 1956; Arnott 1957; Banham

1961; Pringle 1960). T. pilosa overwinter as an egg laid

under bark or in duff at the base of big sagebrush

plants. Eggs hatch in late spring, and larvae crawl up

the main trunks and move out to the tips of branches

where they feed on the epidermis of big sagebrush

leaves and pass through several stages. Mature larvae

are about a half inch long and metallic blue. In early

July, mature larvae move down the host plants into

duff at the base of the plant to pupate. After 1 to 2

weeks, adult beetles, shiny green, emerge and move up

the host plant to feed on leaves, buds, and tender

twigs. Pringle (1960) found rigid host specificity. In his

study, adult beetles starved to death when placed on

four other sagebrush species common to his study area

as well as on rabbitbrush and goldenrod.

Amount of big sagebrush killed by infestations of

this insect varied from a few acres to a few thousand

acres (Banham 1961; Pringle 1960). Pringle (1960, p.

139) observed:

In the spring of 1955, visual observations showed that

90 percent of the sagebrush over the original two-acre

patch was dead. It was most interesting that the shrubs

used by ants as aphid pasture were not damaged to any

degree and hence survived to stand out like flags. In

some cases the ants died out and plants protected in

this manner were utilized and killed in the following

season by hatching larvae.

Defoliator

An important pest of big sagebrush is a defoliator, a

single insect species of moth (Aroga websteri) that

damages to varying degrees vast acres of big sagebrush habitat over widespread areas in California,

Idaho, Montana, Nevada, Oregon, Utah, and Washington (Anonymous 1963; Furniss and Carolin 1977;

Gates 1964; Hall 1963, 1965; Hsiao 1986).

The sagebrush defoliator, also known as webworm,

is a small gray moth with a wing span of 9

⁄

16 to 5

⁄

8 inch

that has black markings on the front wings. Eggs are

white, and mature larvae have a brown head with a

creamy white body and a row of black spots on either

side of the abdomen (Hall 1965). This insect produces

just a single generation per year and overwinters in

the egg stage as a fully developed embryo (Hsiao 1986).

Hsiao (1986) described the sagebrush defoliator’s

life history. Eggs are laid under the bark and hatch

into larvae during early spring. The larvae feed on

sagebrush foliage, starting with young leaves near the

end of short shoot, and they construct web tubes from

the main webbing sites as they grow. Feeding is done

at night, and then the larvae return to the main

webbing site where they remain inside the protective

cover of the webbing site during the day. This continues until they reach the five instar stage, then pupation starts. Pupation occurs among leaves and stems

(Hall 1965) and adults emerge. The adults are also

nocturnal, like the larvae, and start laying eggs in late

July to early August. Most of the eggs enter an embryonic diapause.

Hsiao (1986, p. 195) described the effects of the

sagebrush defoliator:

In general, an increase in the number of defoliators was

associated with a decrease in the number of flower

stalks (the reproductive tissue of the plant). The number of flower stalks was also positively correlated with

the weight of the plants, and may reflect the plant’s age

and reproductive potential. Foliage production also

decreased as the number of defoliators increased.

Of course, mortality of branches and whole plants

increased with increasing numbers of the insect.

As with all other living organisms, Aroga websteri

comes with its own set of parasites, predators, and

diseases (Furniss and Barr 1975; Hall 1963,1965;

Hsiao 1986). During his study, Hsiao (1986) found 10

species of insect parasites, one insect predator, and

one disease-causing organism attacking the sagebrush

defoliator. These and certain abiotic agents influence

the size of the sagebrush defoliator populations. Hsiao

(1986, p. 196) felt that abiotic factors were the most

important: “Weather affects the defoliator population

through the insect’s host plants. Hot, dry periods

cause water stress on the sagebrush plants and reduce

moisture in the foliage, thus reducing foliage acceptability to the defoliator larvae, especially during their

prime feeding period.” High moisture years favor outbreaks.

Other species of Artemisia are attacked by the sagebrush defoliator, but as Hsiao (1986) noted, big sagebrush and three-tipped sagebrush (Artemisia

tripartita) are the most important natural hosts and

serve as another example of big sagebrush playing a

key role in another insect life cycle.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 91

Another moth species, a leaf miner (Bucculatrix

tridenticola), can also cause heavy defoliation of big

sagebrush, as can perhaps still another moth, B.

seorsa (Hall 1963, 1965). To date, three species of

moths are known to feed on big sagebrush, which in

turn have 10 insect parasite species, one insect predator, and a disease organism.

Crickets, Grasshoppers, and Katydids

Interestingly, big sagebrush tops the menu for Mormon crickets (Anabrus simplex; fig. 3.11). According to

a study conducted northeast of Dinosaur, CO, by

Redak and others (1992), the diet of Mormon crickets

was 51 percent big sagebrush, 23 percent forbs, 7

percent grasses, 6 percent arthropods, and small

amounts of moss, fungi, and seeds. Even with removal

of 75 percent of the big sagebrush plants, Mormon

crickets still chose to eat large amounts of big sagebrush. Redak and others (1992, p. 100) concluded:

“Despite the reputation of Mormon cricket as a rangeland pest, we found little evidence that this insect

significantly affects understory vegetative biomass or

production of palatable forages. Likewise, Swain (1944)

rarely found severe damage to forage in heavily cricketinfested sites in Nevada.” They questioned the need

for aerial spray control programs for Mormon crickets,

and suggested that crickets may actually make a net

“improvement” to range condition by removing some

of the big sagebrush overstory.

During a Mormon cricket outbreak in 1999 in an

area about 1 mile southeast of the Juab-Tooele County

line in Utah on U.S. Highway 6, I observed tens of

thousands of the crickets marching along the highway

headed in a southeasterly direction. The mean number of crickets on big sagebrush plants was five. Rarely

did I observe crickets on the Utah juniper (Juniperus

osteosperma) plants that were interspersed among the

big sagebrush plants. Occasionally I found patches of

some 15 to 20 big sagebrush plants where all leaves

had been consumed by Mormon crickets along with

portions of stems and bark, but most big sagebrush

plants were only little consumed. Forbs were more

heavily utilized than were grasses but neither to

excess.

Some species of grasshoppers also consume large

quantities of big sagebrush, even to the point of killing

big sagebrush plants (table 3.5; fig. 3.12) (Allred 1941;

Graham and others 1995; Sheldon and Rogers 1978).

Figure 3.11—Mormon cricket feeding on big sagebrush

(photos by Bruce L. Welch).

Table 3.5—Grasshopper species that eat big

sagebrush (Anonymous 1992;

Hewitt and others 1974; Isely 1944;

Johnson and Lincoln 1990, 1991;

Scharff 1954; Sheldon and Rogers

1978).

Ageneotettix deorum

Ageneotettix elliotti

Apote notabilis

Aulocara elliotti

Conozoa wallula

Melanoplus cinereus

Melanoplus differentialis

Melanoplus mexicanus mexicanus

Melanoplus sanguinipes

Melanoplus yarrowii

Oedaleonotus enigma

Trimerotropis caeruleipennis

Figure 3.12—Grasshopper feeding on big sagebrush (photo by

Bruce L. Welch).
92 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Sheldon and Rogers (1978), studying the food habits of

eight species of grasshoppers, found that seven of the

eight consumed some big sagebrush, but Melanoplus

cinereus was the champion big sagebrush eater (61

percent of its diet). Sheldon and Roger (1978) reported

the amount of big sagebrush in the diet of other species

of grasshoppers as 47 percent for Oedaleonotus enigma,

18 percent for Apote notabilis, 12 percent for Melanoplus

yarrowii, 6 percent for Trimerotropis caeruleipennis, 4

percent for Ageneotettxi deorum, 1 percent for Conozoa

wallula, and 0 percent for Hesperotettix viridis. Sheldon

and Rogers (1978, p. 89–90) further observed:

The combined results for all grasshopper species ...

show that the diet frequency of 41% for big sagebrush

is more than twice that of any other vascular plant.

These results correct the statement by Daubenmire

(1975) that the foliage of big sagebrush is not eaten by

grasshoppers. He states that grasshoppers “congregate

on big sagebrush at night, roosting on the canopy.” We

confirmed this and also found that during the heat of

the day many species of grasshoppers sit on big sagebrush to avoid the high temperatures of exposed soil

surface areas.

Allred (1941) noted that Melanoplus mexicanus readily

fed on big sagebrush over large areas in eastern

Montana, even when grasses were available. Table 3.5

lists the grasshopper species, 12 in all, that eat various

amounts of big sagebrush. Graham and others (1995)

reported in test gardens that grasshoppers (species

unknown) browsed more on hybrid big sagebrush

plants than on the parental lines of mountain and

basin big sagebrush. Scoggan and Brusven (1973),

studying the grasshopper-plant community associations in Idaho, found that 24 species of grasshoppers

were associated with big sagebrush.

Fielding and Brusven (1992) found that two agricultural pest grasshoppers ( Aulocara elliotti and

Melanoplus sanguinipes) population densities were

lower on big sagebrush sites than on crested wheatgrass and cheatgrass sites; or in other words, range or

biodiversity improvement projects may stimulate or

support the buildup of grasshopper pests. Based on

these observations these two workers expanded their

observations.

Fielding and Brusven (1994), conducted a study to

determine effects of habitat degradation and shrub

loss due to range improvement (seedling of crested

wheatgrass, Agropyron cristatum) and fire frequency

associated with the invasion of cheatgrass (Bromus

tectorum) on grasshopper density and species richness. They selected five vegetation types within a

small geographic area to factor out effects of local

weather patterns. Three of the vegetative types were

dominated by big sagebrush (probably Wyoming big

sagebrush subdominated by bluebunch wheatgrass,

Agropyron spicatum, or crested wheatgrass, or

cheatgrass), one dominated by crested wheatgrass,

and one dominated by cheatgrass/medusahead wildrye

(Taeniantherum asperum). Fielding and Brusven

(1994, p.162) reported: “Grasshopper density was lowest and species diversity was highest in vegetation

types with shrub cover. Annual grasslands had the

highest grasshopper densities and the lowest species

diversity, and were dominated by generalist species

with wide diet breadths.” A comparison of the density

of grasshopper and species richness of the big sagebrush/crested wheatgrass vegetation type to the crested

wheatgrass/cheatgrass type showed only a difference

in the amount of big sagebrush. The range improvement or crested wheatgrass sites were found to have a

higher density of grasshoppers (1.18 versus 0.68) with

a lower richness of species (six versus nine) but contained twice the percentage of the pest grasshopper

Melanoplus sanguinipes. This particular species of

grasshopper will migrate from wildland to irrigated

cropland where it becomes a major problem. Fielding

and Brusven (1994, p. 165) concluded that “these

results indicate that areas with shrub cover and an

understory of perennial grasses will have lower overall grasshopper densities with a lower proportion of

pest species.” Given these study results, one could ask

if the cost of combating insect pest problems due to the

killing of big sagebrush should be added to the cost of

range improvement programs.

Fielding and Brusven’s (1994) work is supported by

an early report by Scoggan and Brusven (1973). They

also found that grasshopper density was greater after

big sagebrush control, and species richness less. Hewitt

and Onsager (1988) also noted an increase in the

density ofMelanoplus sanguinipes with the removal of

big sagebrush.

Long horned katydids and green grasshoppers also

feed on big sagebrush. Tinkham’s (1944) study on the

shield-back katydids of the North American deserts

reported finding 10 species of this group peculiar to big

sagebrush as a host plant, and two other species were

also found on big sagebrush and other plants species,

for a total of 12 (table 3.6).

Cicadas

Cicadas are large insects 1 to 2 inches in length,

nonjumping, and the males usually have a soundproducing organ at base of the ventral side of the

abdomen (Borror and White 1970). After mating (early

summer) adult females use their sharp ovipositor to

form slits in the bark of woody plants where eggs are

deposited and hatch in a few days (Hugie and Passey

1963). Hatchlings, called nymphs, drop to the ground

and burrow into the soil where they stay for 2 to 6 years

feeding on the roots of plants, after which they emerge

as adults to mate and lay eggs for the next generation

(Hugie and Passey 1963). Sugden (1940) found seven

species of cicadas living in an association with big
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 93

sagebrush: Neoplatypedia constricta, Platypedia

putnami lutea, Okanagana fumipennis, O. luteobasalis,

O. striatipes, O. vanduzeei, and O. utahensis. Damage

to plants by root feeding cicada nymphs is unknown,

but their effects on soil genesis can be substantial

(Hugie and Passey 1963).

Thrips

Thrips are small, slender insects 1⁄

64 to 3

⁄

16 inch in

length with four hairy wings (Tingey and others 1972).

Mouthparts are rasping-sucking and thus obtain food

by sucking out the contents of plant cells or other

insects and mites (Borror and White 1970). Damage to

plants is confined to localized killing of cells and

perhaps to developing seeds. Sixteen thrips species

have been collected from big sagebrush (table 3.7).

Some are obligates.

Gall Inducers

Felt (1916) is the earliest work that I could find

concerning insects inducing galls on big sagebrush. He

described three species of midges, small flylike insects

that resemble a mosquito, that were hatched from

galls, and which presumably induced gall formation.

These three species were Diarthronomyia artemisiae,

D. occidentalis, and Rhopalomyia ampullaria. To this

list, Felt (1940) added the following gall-inducing

midges: Rhopalomyia navasi, R. tridentatae, Trypetid

(fly), and Cecidomyia sp. Each species induces a gall

that is unique in shape, size, placement, texture, color,

and pubescence, so much so that a dichotomous key

was constructed as an aid in species identification

(fig. 3.13). Later, Jones and others (1983) described 26

species of midges that induce galls on big sagebrush in

Idaho. Table 3.8 lists 32 species of midges that induce

Table 3.6—Shield-back katydids

using big sagebrush as

a host (feed) plant

(Tinkham 1944).

Aglaothorax segnis

Ateloplus hesperus

Idiostatus elegans

Idiostatus hendersoni

Idiostatus inermis

Idiostatus inyo

Idiostatus magnificus

Idiostatus nevadensis

Idiostatus variegatus

Neduba carinata

Plagiostira albontata

Plagiostira gillettei

Table 3.7—Thrips species collected

from big sagebrush

(Bailey and Knowlton

1949; Knowlton and

Thomas 1933; Tingey

and others 1972).

Anaphothrips obscurus

Anaphothrips tricolor

Aptinothrips rufus

Frankliniella minuta

Frankliniella moultoni

Frankliniella occidentalis

Frankliniella tritici

Frankliniella sp. unknown

Frankliniella sp. unknown

Leptothrips mali

Leptothrips sp.

Odontothrips loti

Rhopalandrothrips corni

Sericothrips sp. unknown

Sericothrips sp. unknown

Thrips tabaci

Figure 3.13—Various insect galls growing on big

sagebrush except lower right corner which was

induced by a fungus (photos by Bruce L. Welch)
94 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

gall formation on big sagebrush. In addition to galls

induced by midges, Foote and Blanc (1963) and Fronk

and others (1964) described several species of fruit

flies that also induce gall formation on big sagebrush:

Asphondylia sp., Aciurina maculata, Eutreta diana,

E. oregona, Neotephritis finalis, Orellia undosa, Oxyna

palpalis, O. utahensis, and Trupanea nigricornis.

Emlen (1992) described an additional gall-inducing

fruit fly, Eutreta diana. In all, 42 species of insects are

known to induce galls on big sagebrush.

But the story does not stop with these 42 insect

species. Fronk and others (1964) found two species of

parasitic Hymenoptera, Tetrastichus sp. and Dacnusa

sp., that are parasitoids on some of these gall-inducing

insects. Jones and others (1983) described an additional 11 insects that are associated with these gallinducing midges. Some were parasites on larva, pupa,

and adults, and others were nonharmful associates.

These 11 species were: Apion sordidum, Encyrtidae

sp., Eupelmidae sp., Platygaster utahensis, Platygaster

sp., Pogonomyrmex owyheei, Pteromalinae sp.,

Reduviolus alternatus, Synopeas sp., Torymus

aeneoscapus, and Torymus koebelei. Emlen (1992),

studying a high-altitude population of Eutreta diana,

found two more parasitic Hymenoptera species parasitizing this gall inducer (Torymus citripes and Zatropis

sp.). So great was the parasitism that only 2 percent of

the galls contained live larvae. Still, two more parasitic Hymenoptera species reared from insect galls on

big sagebrush were described by Santiago-Blay (1989)

(Eurytoma sp. and Sympiesis sp.). A study by Goeden

(1990) described three more Hymenoptera parasitic

species on the gall former Eutreta diana—Eupelmus sp.,

Pteromalus sp., Rileya sp. Goeden (2002) described

Oxyna palpalis (Coquillett, Dipters: Tephritidae) as a

facultative predator of Rhopaloymyia florella making a total of 21 species. Goeden (1990) found two

species that were described as gall miners, Apion sp.

(Coleoptera: Apionidae) and Liriomyza (Diptera:

Agromyzidae). Goeden (1990, p. 31) described an avian

predator: “However, the more common predators of E.

diana larvae and puparia were birds, which were

especially active at the Mormon Rocks study site,

where many galls bore open holes pecked by social,

insectivorous bushtits, Psaltriparus sp.” I observed

mountain chickadees (Parus gambeli) preying on insect larvae inside of mountain big sagebrush galls on

April 2002 at the Great Basin National Park.

Fronk and others (1964, p. 575) stated, “It is well

known that some insects use galls as places to overwinter.” They described the following insect species as

possible hibernators in galls of big sagebrush:

Coleophora sp., Thiodia or Eucosma sp., Bucculatrix

sp. (all Lepidotera), Brachyrhinus ovatus (a Coleoptera), Miridae genus, and Nabidae Nabis sp. (last

two are nymphs, Hemiptera). In summary: 42 insect

species have been described as inducing gall formation

on big sagebrush, 20 insect species as parasitizing the

gall or gall inducers, six species that use galls on big

sagebrush as a hibernacula, and two bird species that

eat the larvae inside of galls. This is an interesting

ecosystem with big sagebrush as the keystone plant

species.

Ants

In a big sagebrush community near Twin Falls, ID,

Cole (1933) found seven species of ants (Formica fusca,

F. fusca neorufibarbis, F. pallide-fulva, F. rufa

obscuripes, F. sanguinea subnuda, F. subpolita, and

Pogonomyrmex occidentalis)that were associated with

big sagebrush (fig. 3.14). Sneva (1979) listed one more

species occurring in the big sagebrush type, P. owyheei;

Blom and others (1991) listed one more, P. salinus;

Table 3.8—Midges that induce galls

on big sagebrush (Felt

1916, 1940; Jones and

others 1983).

Cecidomyia spp.

Diarthronomyia artemisiae

Diarthronomyia occidentalis

Rhopalomyia ampullaria

Rhopalomyia anthoides

Rhopalomyia brevibulla

Rhopalomyia calvipomum

Rhopalomyia conica

Rhopalomyia cramboides

Rhopalomyia culmata

Rhopalomyia florella

Rhopalomyia gossypina

Rhopalomyia hirtibulla

Rhopalomyia hirticaulis

Rhopalomyia hirtipomum

Rhopalomyia lignea

Rhopalomyia lignitubus

Rhopalomyia mammilla

Rhopalomyia medusa

Rhopalomyia medusirrasa

Rhopalomyia navasi

Rhopalomyia nucula

Rhopalomyia obovata

Rhopalomyia pomum

Rhopalomyia rugosa

Rhopalomyia sp.

Rhopalomyia sp. near lignea

Rhopalomyia tridentatae

Rhopalomyia tubulus

Rhopalomyia tumidibulla

Rhopalomyia tumidicaulis

Trypetid sp.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 95

Lygus hesperus (Scott 1977), Lygus robustus (Knight

1921), Orthezia artemisiae (Furniss and Barr 1975),

and Cercopeus artemisiae (Graham and others 1995).

• In summary, the following numbers of insect

species have been found on or in big sagebrush: 52

aphids and 10 parasites

• 23 beetles

• 3 moths

• 1 Mormon cricket

• 12 grasshoppers

• 12 katydids

• 7 cicadas

• 16 thrips

• 42 gall inducers and 21 parasites

• 2 gall miners

• 6 gall hibernators

• 23 ants

• 7 miscellaneous

Total: 237 insect species are associated with big sagebrush (fig. 3.15). This explains the large number of

insect-eating birds, mammals, and reptiles all living

within the big sagebrush ecosystem (see chapter II).

Spiders

Spiders are predaceous Arachnida having four pairs

of legs but lacking antennae or wings, with a body

composed of two parts attached by a narrow stalk—

cephalothorax and abdomen (fig. 3.16) (Borror and

White 1970). They feed on insects and other small

animals by paralyzing them through injection of venom

Figure 3.14—An ant attending aphids on big sagebrush (photos by Bruce L. Welch).

and Graham and others (2001) listed one more, Formica

dakotensis. Both Furniss and Barr (1975) and Cole

(1933) reported higher colony densities in big sagebrush than for other vegetative types. Allred and Cole

(1971, p. 238), in their study of ants of the National

Reaction Testing Station near Idaho Falls, ID, observed: “Ants representing the greatest number of

species were found in the Artemisia-Chrysothamnusgrass and Artemisia associations, and fewest were

found in the Juniperus, Chenopodium-Eurotia, and

Oryzopsis-Stipa associations.” The Artemisia of their

study was big sagebrush. Allred and Cole (1971) captured 15 species of ants living in association with big

sagebrush; 12 of those were species not listed by

workers cited earlier in this chapter: Camponotus

vicinus, Formica haemorrhoidalis, F. manni, F.

montana, F. neogagates, F. obtusopilosa, F. oreas,

Lasius crypticus, Monomorium minimum, Mymica

lobicornis, Myrmecocystus mojave, and Tapinoma

sessile. So, 23 species of ants are found living in

association with big sagebrush. Furniss and Barr

(1975)noted that these ant species defoliate numerous

annual and perennial plants, particularly in the immediate area surrounding their mounts, and they also

can defoliate big sagebrush. Ants protecting their

aphids pasturing big sagebrush plants have been

discussed in the aphid section (fig. 3.14). Heikkinen

(1999) found that the presence of the western thatching ant (Formica obscuripes) reduces the number of

spiders found on big sagebrush plants.

Other insect species reported as associating with big

sagebrush include: Apterona crenulella (Furniss and

Barr 1975), Clastoptera atrapicata (Hamilton 1977),

Hippodamia apicaulis (Graham and others (2001),

Figure 3.15—A potpourri of insects on big sagebrush

(photo by Bruce L. Welch).
96 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Figure 3.16—A potpourri of spiders on big sagebrush (photos by Bruce L. Welch).

from ducts through the fangs leading from the poison

glands.

Studies conducted by Abraham (1983), Allred (1969),

Ehmann (1994), and Hatley and Macmahon (1980)

found 72 spider species in or on big sagebrush plants

(table 3.9). Spiders spread from big sagebrush plant to

big sagebrush plant by two dispersal modes: longdistance, passive, aerial dispersal called ballooning

(here, the spider climbs onto a branch and releases silk

into the wind until the wind lifts the spider off its perch

and it floats to a new area) and local, active, ground

dispersal (Ehmann 1994; Hatley and Macmahon 1980).

Allred (1969, p. 108), studying the spiders of the

National Reactor Testing Station in Idaho, observed:

“The greatest variety of species was found in study

area 10 where the vegetation analysis was 68% Artemisia, 7% Opuntia, 7% mixed grasses, and 5% miscellaneous forbs. The fewest numbers of species were

found in study areas 7 and 11, typified predominantly

by Chrysothamnus plants.” Hatley and Macmahon
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 97

Table 3.9—Spider species associated with big sagebrush listed by guild (Abraham 1983; Allred

1969; Ehmann 1994; Hatley and Macmahon 1980).

Jumpers

Metaphidippus aeneolus

Oxyopes scalaris

Phidippus johnsoni

Sassacus papenhoei

Synageles idahoanus

Tutelina similis

Trappers

Dictyna idahoana

Dipoena nigra

Dipoena tibialis

Euryopis sp.

Hyposinga singaeformis

Metepeira foxi

Theridion neomexicanum

Theridion petraeum

Ambushers

Coriarachne sp.

Misumenops sp.

Xysticus cuncator

Xysticus gulosus

Xysticus montanensis

Pursuers

Anyphaena pacifica

Chiracanthium inclusum

Ebo sp.

Philodromus histrio

Additional species from Allred (1969)

Ceratinella acerea

Ceratinella parma

Circurina new species

Dictyna coloradensis

Drassyllus mannellus

Enophognatha wyuta

Gnaphosa

Haplodrassus eunus

Schizocosa avida

Tarentula kochi

Zelotes pullatus

Xysticus knowltoni

Xysticus nigromaculatus

Additional species from Abraham (1983)

Aculepeira verae

Alopecosa kochi

Araneus gemma

Araniella displicata

Argiope trifasciata

Dictyna completa

Ebo evansae

Enoplognatha ovata

Erigone dentosa

Euryopis scriptipes

Herpyllus sp.

Latrodectus hesperus

Meioneta sp. 1

Meioneta sp. 2

Meioneta sp. 3

Metaphidippus verecundus

Metaphidippus sp.

Micaria sp.

Misumenops asperatus

Misumenops lepidus

Neoscona arabesca

Pardosa wyuta

Pellenes hirsutus

Phidippus octopunctatus

Philodromus californicus

Philodromus rufus

Philodromus satullus

Philodromus speciosus

Spirembolus mundus

Steatoda americana

Synagales sp. nov.

Tetragnatha laboriosa

Thanatus formicinus

Tibellus chamberlini

Tibellus oblongus

Zelotes subterraneus

(1980) reported greater numbers of spiders and greater

diversity of spider species on big sagebrush plants

having greater foliar density. Abraham (1983) reported similar results. With the large numbers of

insects associated with big sagebrush, it is not surprising that a large number of spider species are there to

prey on this large food base (Welch and Criddle 2003).

Scorpions

Scorpions are also predaceous Arachnida, large,

with pincers and a long segmented abdomen that

usually curves upward and ends in a stinger at the tip.

They are largely nocturnal and feed chiefly on insects

and spiders. Allred (1973) found the scorpion species

Paruroctonus boreus in big sagebrush and two other

shrub communities in Idaho. He noted a strong correlation between scorpion number and the abundance

of ants and spiders. Ideal scorpion habitat was described as having bare ground cover of less than 15

percent, at least 5 percent grass cover, and 60 percent

or more broad-leaf shrubs cover (big sagebrush, rabbitbrush, Chrysothamnus sp., horsebrush,

Tetradymia).
98 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Wiens and others (1991), studying the interrelationships between leaf-tissue secondary chemistry, avian

predation, and the abundance and diversity of

arthropods occurring on big sagebrush in central Oregon, collected 168 arthropod species from big sagebrush. I have listed 309 in this chapter.

Lichens________________________

Lichens, composed of a fungus partner and either a

population of unicellular or filament algal or

Figure 3.17—Lichens growing on mature big sagebrush plants (photos by Bruce L. Welch)

cyanobacterial cells, are found growing on the bark of

mature big sagebrush plants (fig. 3.17). Rosentreter

(1990) reported finding 24 species (table 3.10) growing

on the trunk of big sagebrush. Some species were

found on all three subspecies of big sagebrush, others

on just one or two. He described 21 species growing on

basin big sagebrush, 17 on Wyoming big sagebrush,

and nine on mountain big sagebrush. Rosentreter

(1990) found that the key factors influencing the

amount of lichen cover on big sagebrush were: canopy

density (open more light), shrub growth rate (slower),
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 99

Table 3.10—Lichen species associated with big sagebrush

(Rosentreter 1990).

Buellia punctata

Caloplaca fraudans

Candelaria concolor

Candelariella rosulans

Candelariella vitellina

Hypogymnia physodes

Lecanora cf. varia

Lecanora sp.

Lecidea plebeja

Lepraria neglecta

Letharia vulpina

Melanelia exasperatula

Melanelia incolorata

Physcia dimidiata

Physcia sp.

Physconia detersa

Physconia grisea

Physconia muscigena

Rinodina sp.

Usnea sp.

Xanthoria candelaria

Xanthoria fallax

Xanthoria polycarpa

Xanthoria sorediata

bark stability (less sloughing), and pH. Daubenmire

(1970) collected 11 species of lichens growing on the

stems of big sagebrush in Washington.

Parasitic Plants _________________

Paintbrushes

Paintbrushes, Castilleja, are flowering facultative

root hemiparastic plants that add a splash of color

throughout the big sagebrush ecosystem (Taylor 1992;

fig. 3.18). About 16 species are known to use big

sagebrush as a host plant (Cronquist and others 1984;

Goodrich and Neese 1986; Hitchcock and others 1959;

table 3.11). From the big sagebrush host, paintbrushes

receive water, solubles, and organic compounds

(Ducharme and Ehleringer 1996; Hansen 1979; see

chapter IV). These paintbrushes are perennials with

woody, well-branched root systems and herbaceous

aboveground stems. Their flowers are small and

nonshowy but bloom among several colorful bract-like

leaves that vary in colors of yellows, reds, oranges, and

purples (Taylor 1992).

Matthies (1997) using greenhouse techniques found

that Castilleja chromosa (desert paintbrush) grew

larger in the presence of a host than alone and that it

Table 3.11—Paintbrushes (Castilleja)

associated with big sagebrush (Cronquist and others 1984; Goodrich and

Neese 1986; Hitchcock

and others 1959).

Castilleja angustifolia

Castilleja applegatei

Castilleja aquariensis

Castilleja chromosa

Castilleja cusickii

Castilleja dissitiflora

Castilleja flava

Castilleja linariifolia

Castilleja miniata

Castilleja pallescens

Castilleja pilosa

Castilleja oresbia

Castilleja rustica

Castilleja scabrida

Castilleja thompsonii

Castilleja xanthotricha

Figure 3.18—Desert paintbrush—Castilleja chromosa—

parasitizing mountain big sagebrush (photo by Bruce L.

Welch).

grew larger with alfalfa as the host plant than with a

grass host. I have observed in the field that desert

paintbrush plants growing within 48 inches of big

sagebrush plants seem taller than those growing more

than 48 inches from the center of big sagebrush plants.

I collected data, height of desert paintbrush plants,

and distance from the center of big sagebrush host

plants, from West Mountain located about 14 miles

southwest of Provo, UT (table 3.12). I found that there

was a significant drop in desert paintbrush plant
100 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 3.12—The relationship between height of desert paintbrush (Castilleja

chromosa) plants and distance from the center of big sagebrush

(Artemisia tridentata) host plant. Break point or distance from

center of big sagebrush where height of desert paintbrush was

significantly decreased occurred at 47 inches. This was determined

by a piecewise linear regression model (Neter and others 1989).

From center of big sagebrush plant Height of desert paintbrush

- - - - - - - - - - - - - - - - - - - - - - - - - Inches - - - - - - - - - - - - - - - - - - - - - - - - - -

2 31

3 14, 22, 24

4 23

5 24

6 18, 21

7 29

8 23

9 21

10 24, 25 19, 19,

11 28, 23

12 15

13 20

14 26

15 15

16 15, 24

18 14, 17

19 19, 13, 15

20 18

21 35

23 18, 16

25 18

27 16

28 15

30 14

36 18

37 11

38 10, 6

39 8, 5

40 10

42 8

44 5, 8

45 12, 5

47 8

48 5, 5, 6, 9

49 6, 6

50 5

51 4, 9

52 7

54 6, 7

55 8

56 9

57 9

59 8

60 5

62 7

64 9, 8

65 7

70 6

72 5

74 7

77 8

79 6, 7
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 101

heights that were growing farther than 47 inches from

the center of big sagebrush host plants.

Owl-Clovers

Owl-clovers (Orthocarpus) are facultative root

hemiparasites but unlike paintbrushes are smaller

and are annuals. They are not as colorful as the

paintbrushes but their bract-like leaves do vary in

color—yellows, violets, purples, and reds. Seven species have been identified as using big sagebrush as

host plants: Orthocarpus barbatus, O. copelandii, O.

hispidus, O. luteus, O. purpureo-albus, O. tenuifoliun,

and O. tolmiei (Cronquist and others 1984; Ducharme

and Ehleringer 1996; Goodrich and Neese 1986; Taylor 1992).

Other Parasitic Plants

A number of other facultative root parasites may use

big sagebrush as host plants. These include: Bird’s

beaks—Cordylanthus capitatus, C. kingii, C.

parviflorus, C. ramosus, C. wrightii; and Broomrapes—

Orobanche corymbosa, O. fasciculata, O. ludoviciana

(Cronquist and others 1984; Goodrich and Neese 1986).

A large number of flowering root parasites may receive

nourishment from big sagebrush. Counting all the

organisms listed in this chapter that receive some, and

in many cases all, of their sustenance from big sagebrush, the title “mother sagebrush” seems appropriate.

Sego Lilies in a Stand of Wyoming

Big Sagebrush __________________

During a pygmy rabbit (Brachylagus idahoensis)

survey (June 2003) south of the Painted Rocks area

(about 6 miles due east of the Yuba State Park) of

central Utah, I observed that the vast majority of sego

lily (Calochortus nuttallii) plants were growing under

the canopy cover of Wyoming big sagebrush. I conducted a half mile long by about 15 feet wide belt

transect and noted the location, either under the

canopy of a Wyoming big sagebrush plant or outside

the canopy, of each sego lily plant encountered. I

encountered 482 sego lily plants. A total of 81 percent

(391) of the sego lily plants were growing under the

canopy cover of Wyoming big sagebrush plants with 19

percent (91) growing outside the canopy. The sego lily

plants growing under the canopy cover of Wyoming big

sagebrush appeared to be taller and to produce more

flower heads per plant (fig. 3.19).

Figure 3.19—Photographs showing sego lily

(Calochortus nuttallii) plants and perennial grass

plants growing under the protective cover of

living and dead Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) plants. It

was found that 94 percent of the perennial grass

cover on this site was under the protective cover

of Wyoming big sagebrush plants. Cattle were

allowed to grazed this site, in spite, of the

general lack of grasses and forbs in the

interspaces between Wyoming big sagebrush

plants and the continuation of a five year drought

(photo by Bruce L. Welch).
102 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

To test the above hypothesis, sego lily plants growing in the interspaces between Wyoming big sagebrush plants were paired (24) with sego lily plants

growing within 10 feet under the canopy cover. Measurements taken were height (inches) and number of

flower heads per plant. Paired data sets, height and

flower number per plant, were statistically compared

using paired T-test at the 5 percent probability level

(Hintze 1992). Results from the 24 pairs showed that

the sego lily growing in the interspaces were significantly shorter (5.34 ± 1.26-range 3.75 to 8.0 inches)

than those growing under the canopy cover (16.93 ±

3.33-range 11.5 to 24.5 inches). Number of flower

heads was significantly less for those growing in the

interspaces (1.29 ± 0.46-range 1 to 2) than those

growing under the canopy cover (1.96 ± 0.36-range 1 to

2). This would indicate that sego lily plants growing

under the canopy cover of Wyoming big sagebrush

were more vigorous and achieved a higher reproductive potential than those growing in the interspaces

between Wyoming big sagebrush plants.

Four possible reasons explain these observations.

First, the nutrient content of soil is higher under the

big sagebrush plants (see chapter IV for details);

second, favorable surface water relationships last

longer under the canopy cover (see chapter IV); third,

hydraulic lift of water by big sagebrush supplies more

water to the sego lily plants growing under the canopy

(see chapter IV); and fourth, the canopy cover protects

the sego lily plants from grazing livestock.

During the study time, the general area was suffering from a combination of abusive grazing practices

and a continuing 5 year drought. A 300-foot line

intercept vegetative analysis was conducted to determine the cover values of big sagebrush, bare ground,

grass, and percent of grass under the big sagebrush

plants. The line transect started at a point located at

N 39° 20.625; W 111° 57.428 and went northeast for

300 feet. Results were: Wyoming big sagebrush canopy

cover 28 percent, bare ground 43 percent, and grass

cover 9 percent with 94 percent of the grass occurring

under the protective cover of the Wyoming big sagebrush plants (fig. 3.19). Livestock were being allowed

to graze this area at the time this study was conducted

(June 2003).

I found the same relationship between sego lily and

Wyoming big sagebrush at two other sites. (I used the

same statistical/experimental design as with the first

site; paired T-test of 24 pairs; Hintze 1992). One site

was at the Gordon Creek Management Area Near

Helper, UT, at N 39° 39.566'; W 110° 55.091'. Here 71

percent of the sego lily plants were found under the

canopy cover of Wyoming big sagebrush plants. Canopy

cover of Wyoming big sagebrush was 14 percent. Sego

lily plants growing under the canopy cover were significantly taller at 13.90 ± 3.0 inches, range 9.25 to

21.0 inches. Those growing in the interspaces between

Wyoming big sagebrush plants were significantly

shorter at 5.7 ± 1.3 inches, range 3.0 to 7.5 inches. Sego

lily plants growing under the canopy cover of Wyoming big sagebrush produced significantly more flower

heads—2.5 ± 0.7 versus 1.4 ± 0.50 for those growing in

the interspaces between Wyoming big sagebrush

plants.

The second site (not recently grazed) was about 5.5

miles west of Lehi, UT, at N 40° 22.736'; W 111°

59.211'. (I used the same statistical/experimental design as with the first site; paired T-test of 24 pairs;

Hintze 1992). Here 64 percent of the sego lily were

growing under the canopy cover of Wyoming big sagebrush. Canopy cover of Wyoming big sagebrush was 21

percent. Sego lily plants growing under Wyoming big

sagebrush were significantly taller at 10.9 ±2.9 inches,

range 6.75 to 19.5. Sego lily plants growing in the

interspaces of Wyoming big sagebrush were significantly shorter at 5.4 ± 0.9 inches, range 3.75 to 6.5.

Number of flower heads per plant was significantly

greater for the sego lily growing under the canopy

cover of Wyoming big sagebrush at 1.6 ± 0.5 versus 1.0

± 0.2 for plants growing in the interspaces.

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Notes

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Chapter

IV

Big Sagebrush

Chemistry and

Water Relations

Nutritive Value ____________________________________________________

All animals are driven to find the right kinds of food and enough of it (Van Dersal 1938).

The survival and activities of animals depend on food supply. As discussed in chapters

II and III, many animals use big sagebrush directly as a food—sometimes their only

food; thus the nutritive value of big sagebrush is of major importance to the animals

eating it (Welch 1989).

Two morphological characteristics set big sagebrush and other shrubs apart from

grasses and forbs: a deep and extensive root system and a rigid and tall stature. A deep,

extensive root system allows big sagebrush to draw water from a greater volume of soil

than can grasses and forbs. This makes big sagebrush a more dependable forage source

during both seasonal and extended drought (Medin and Anderson 1979). Medin and

Anderson (1979, p. 16) stated: “Observed declines in 1962–1964 yields of true mountain

mahogany and antelope bitterbrush were associated with marked decreases in annual

precipitation. Concurrent stable yields of big sagebrush suggest less susceptibility to

drought or to its secondary effects; hence, it is a more reliable forage source.” A taller and

rigid stature makes big sagebrush more available for consumption during periods of

deep snow (Welch 1989).

To appreciate the nutritive value of big sagebrush, we need knowledge of the nutrient

requirements of animals and how these requirements are expressed. The nutritive

value of any plant should be measured in terms of the plant’s ability to supply the

nutrients needed to meet the physiological requirements of the consuming animal. The

quantity of nutrients needed by animals varies according to species, age, size, and

activity (Welch 1989). Qualitatively, nutrient needs of animals can be placed into five

classes: dry matter intake, energy-producing compounds, protein, minerals, and vitamins (Welch 1989).

Dry Matter

Intake of dry matter by animals varies according to species, weight, and activity of the

animal. Greatest consumption of dry matter, as a proportion of live weight, occurs with
108 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

lactation, followed by growth, gestation, and maintenance (Welch 1989). The amount of dry matter consumed is considerably important to land managers

calculating carrying capacity. Dry matter requirements are expressed as pounds consumed per day per

animal. Dry matter intake of selected animals is given

in table 4.1.

Energy-Producing Compounds

Energy-producing compounds are the single largest

class of nutrients needed by animals (Welch 1989).

Energy is needed to drive the various physiological

processes of the body and to provide movement and

heat. Energy can be derived from a variety of compounds, including sugars, fats, pectin, starch, and

protein, and in the case of ruminants and other animals with fermentation digestion systems, indirectly

from cellulose and hemicellulose.

The energy needs of animals are expressed in several forms such as total digestible nutrient (TDN) and

metabolizable energy. TDN requirements of animals

are expressed as kilograms per animal per day or as a

percentage of the diet. Metabolizable energy requirements of animals are expressed as megacalories per

day or as megacalories per kilogram of dry matter.

Energy needs of animals vary according to weight

and activity of the animal. Larger animals require

more kilograms of TDN per day for a given activity

than do smaller animals. A lactating female requires

more kilograms of TDN per day than a nonlactating

female of similar weight. On a constant weight basis,

lactation requires more energy than any other activity. In descending order of energy needs, lactation is

followed by fattening, growth, gestation, and maintenance. Unfortunately, the TDN content or amount of

metabolizable energy is unknown for many forages.

Table 4.1 expresses the energy requirements of animals in terms of in vitro digestibility. Maintenance

requirement was set at 50 percent in vitro digestibility

with all other activities adjusted accordingly (Welch

1989).

Protein

Animal protein makes up a large chemically related

but physiologically diverse group of compounds. Protein is the major organic compound of the organs and

soft tissues of the body and in other structures including hemoglobin, cyctochromes, and membranes. Enzymes are another functionally important group of

protein compounds.

Because proteins are involved in so many bodily

functions, the animal body needs a liberal and continuous supply. As with energy, the protein requirements of an animal vary according to species, weight,

and activity (table 4.1). For ruminants and other

animals that have fermentation-type digestive systems (horses, rabbits, burros, and so forth), the quality

of the protein is not important—only the quantity. The

protein requirement of an animal is expressed as

grams per day of digestible protein or as a percentage

of digestible protein in the diet. Protein requirement

may also be expressed as grams per day of crude or

total protein or as a percentage of crude or total protein

in the diet. As with energy, the greater the weight of

the animal, the higher are the protein needs, assuming that body activity is held constant. On a constant

weight basis, lactation requires more protein than any

other activity. In descending order of protein needs,

lactation is followed by fattening, growth, gestation,

and maintenance (Welch 1989).

Minerals

Fifteen elements are essential for the health of

animals, and seven are considered major: sodium,

chlorine, calcium, phosphorus, magnesium, potassium,

and sulfur. The remaining eight are classified as trace

elements: iodine, iron, copper, molybdenum, cobalt,

manganese, zinc, and selenium. These essential mineral elements constitute the major components of

bones and teeth, maintain osmotic relations and acidbase equilibrium, play an important role in regulating

enzymatic systems and muscular contraction, and are

constituents of most organic compounds. They are also

important in energy transfer (Welch 1989).

Under most conditions, calcium and phosphorus are

the mineral elements of major concern. Animal needs

for calcium and phosphorus are expressed as grams per

day per animal or as a percentage of the diet (table 4.1).

Larger animals under similar body activity need greater

amounts of calcium and phosphorus than do smaller

animals. With size held constant, lactating animals

require the most calcium and phosphorus, followed by

growth, fattening, gestation, and maintenance.

Vitamins

Vitamins are organic compounds that the body needs

in relatively small amounts. Vitamins are unrelated

chemically but function as metabolic regulators. For

animals capable of supporting microbial fermentation, only vitamin A is of major concern. Vitamin A

combines with a specific protein of the eye to produce

visual purple, which aids night vision. In addition to

visual purple, vitamin A plays an important role in

normal development of bones, in the normal power of

disease resistance, and in maintaining healthy epithelium tissues. Vitamin A is manufactured in the liver

from the plant precursor, carotene. Therefore, the

vitamin A requirement is expressed in terms of carotene as either milligrams per animal per day or milligrams per kilogram of dry matter (table 4.1). With size
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 109

Table 4.1—Nutritive requirements of selected animals (after Welch 1989).Animal weights are in pounds.

Dry In vitro Crude

mattera digestionb protein Calcium Phosphorus Carotenec

lb - - - - - - - - - - - - - - - Percent of dry matter - - - - - - - - - - - - - - - mg/kg

Sheep

 Maintenance

110 2.2 50 8.9 0.30 0.28 1.9

132 2.4 50 8.9 .28 .26 2.0

154 2.6 50 8.9 .27 .25 2.2

176 2.9 50 8.9 .25 .24 2.3

 Last 6 weeks of gestation

110 3.7 53 9.3 .24 .23 3.6

132 4.2 53 9.3 .23 .22 3.9

154 4.6 53 9.3 .21 .20 4.2

176 4.8 53 9.3 .21 .20 4.5

 Lactation

110 3.7 60 11.0 .52 .37 2.6

132 4.2 60 11.0 .50 .36 2.9

154 4.6 60 11.0 .48 .34 3.1

176 6.6 60 11.0 .48 .34 3.3

 Growth

66 2.7 56 10.0 .45 .25 1.5

88 3.1 56 9.5 .44 .24 1.8

110 3.3 56 9.5 .42 .23 2.1

132 3.3 56 9.5 .43 .24 2.5

Cattle

 Maintenance

881 13.4 50 5.9 .18 .18 4.1

1,102 15.9 50 5.9 .18 .18 4.1

1,323 18.3 50 5.9 .18 .18 4.1

 Gestation

881 16.5 50 5.9 .18 .18 4.1

1,102 19.0 50 5.9 .18 .18 4.1

1,323 21.4 50 5.9 .18 .18 4.1

 Lactation

881 23.8 53 9.2 .42 .38 5.7

1,102 26.0 53 9.2 .39 .36 5.7

1,323 28.4 53 9.2 .36 .34 5.7

 Growth

661 19.4 57 10.2 .31 .26 3.2

881 24.3 57 10.2 .21 .21 3.2

1,323 26.5 56 8.8 .18 .18 3.2

Horses

 Maintenance 16.4 50 8.5 .30 .20 2.4

 Gestation 16.4 53 11.0 .50 .35 5.0

 Lactation 21.5 56 14.0 .50 .35 4.1

 Growth 13.2 58 16.0 .70 .50 2.9

 Work

 Light — 53 8.5 .30 .20 2.4

 Moderate — 57 8.5 .30 .20 2.4

 Intense — 58 8.5 .30 .20 2.4

Deer

 Maintenance 2.2 50 7.5 .30 .25 —

 Gestation 2.5 53 9.0 .30 .25 —

 Lactation 3.0 60 10.0 .48 .48 —

 Growth — 56 16.0 .38 .27 —

Small mammals (rabbits, squirrels, foxes)

 Maintenance — — 22.0 .30 .30 8.7

 Gestation — — 38.0 .40 .40 8.7

 Lactation — — 46.0 .60 .60 8.7

 Growth — — 35.0 .40 .40 8.7

Birds (grouse, pheasant, quail, turkey)

 Maintenance — — 12.0 .50 .25 5.9

 Breeding — — 14.0 2.25 .35 5.9

 Growth — — 20.0 .75 .38 5.9

a

 Dry matter intake is expressed as pounds per day per head.

b

 Energy is expressed as a percentage of dry matter digested by in vitro means.Unfortunately, the total digestible nutrients

content or amount of metabolizable energy is unknown for many wildland forages.More information is expressed as in vitro

digestibility.Maintenance was set at 50 percent in vitro digestibility, with other activities adjusted accordingly.

c

 Carotene is expressed as mg/kg of dry matter.
110 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

held constant, a lactating animal requires the most

carotene, followed by fattening, growth, gestation, and

maintenance (Welch 1989).

Factors Affecting Nutritive Content of Big

Sagebrush

Three factors affect the nutritive content of big

sagebrush: season, genetics, and environment. Nutritive content is usually highest during the spring months

and from there declines gradually, reaching a low level

in the winter (Tueller 1979). This decline is illustrated

in table 4.2. Peak crude protein content occurred

during the spring at 15.0 percent for big sagebrush,

13.4 for antelope bitterbrush, and 21.3 for unknown

Nevada grass. Crude protein levels were lowest during the winter at 10.5 percent for big sagebrush, 7.5 for

antelope bitterbrush, and 2.7 for unknown Nevada

grass, with summer and fall levels intermediate. It is

apparent that plant genetics play a role in the amount

of crude protein levels in the dry matter of plant

tissues. Again, an inspection of table 4.2 reveals that

big sagebrush, as a species, is genetically programmed

to contain higher winter levels of crude protein than

antelope bitterbrush, and antelope bitterbrush contains higher winter levels of crude protein than the

unknown grass. Some populations of big sagebrush

contain higher winter levels of crude protein than

others; more on this in chapter V (Welch and McArthur

1979). Elderkin and others (1986) found that irrigated

and fertilized big sagebrush plants contained higher

levels of crude protein and were more heavily utilized

by wintering mule deer than plants not irrigated, and

irrigated but not fertilized (also see Williams 1972).

Bayoumi and Smith (1976) found that spring applications of nitrogen significantly increased the percent of

crude protein in the forage of big sagebrush and that

elk used nitrogen-fertilized plants more heavily than

the unfertilized plants. These two studies demonstrate that environmental factors such as soil fertility

also play a role in determining the amount of nutrients

within the tissues of big sagebrush.

Wambolt (2004) studied the effects of plant age on

the crude protein content of current year leaves and

stems for three subspecies of big sagebrush. He noted

that young plants of mountain and basin big sagebrush did not contain higher levels of crude protein

than mature plants. He did detect a statistically higher

amount of crude protein in young Wyoming big sagebrush plants of 1.2 percentage points (11.25 percent

versus 12.45) over mature Wyoming big sagebrush

plants. His conclusions (Wambolt 2004) were: “I conclude that there is no meaningful difference for herbivores in crude protein levels between the age classes of

the 3 big sagebrush subspecies. The additional 1.2%

crude protein for young Wyoming big sagebrush would

result in a increase of 0.6% digestible protein (Striby

et al. 1987). It would be a rare circumstance when that

level would be significant for wintering ungulates.”

Value of Specific Nutrients in Big

Sagebrush

The nutritive values of big sagebrush are given in

tables 4.3, 4.4, 4.5, and 4.6. Each table represents a

different nutrient: in vitro digestion (table 4.3), crude

protein (4.4), calcium (4.5), and phosphorus (4.6). The

values expressed in the tables are from a number of

independent researchers. Where more than one value

was given in a study for a given season (spring,

summer, fall, and winter), a mean was calculated and

listed as the value for the study. Only studies using

current year’s growth of leaves and stems were quoted

in the tables, because most animals eat both leaves

and stems, with birds and insects as exceptions (personal observations by the author). Data for in vitro

digestion, crude protein, calcium, and phosphorus

were expressed on a dry-matter basis.

The data given in the tables demonstrate the relative stable nutrient content across seasons. For example, calculating seasonal means among the various

studies for in vitro digestibility reveals in vitro digestion ranged from 54 percent (winter), to 59 percent

(spring and fall). All of these values are above the

Table 4.2—Seasonal variation of crude protein for big sagebrush (Artemisia

tridentata), antelope bitterbrush (Purshia tridentata), and an

unknown Nevada grass (after Tueller 1979).

Month/year Big sagebrush Antelope bitterbrush Grass

- - - - - - - - - - Percent of crude protein - - - - - - - - - -

June 1968 11.8 13.4 13.4

July 1968 12.7 12.8 7.8

September 1968 11.8 9.7 9.6

December 1968 10.5 7.5 2.7

March 1969 14.0 9.9 3.4

May 1969 15.0 11.3 21.3
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 111

Table 4.3—In vitro digestibility of big sagebrush (Artemisia tridentata) dry matter by

seasons as reported by various studies.

Spring Summer Fall Winter References

- - - - Percent of dry matter digested - - - -

50 Elderkin and others 1986a

61 Fajemisin and others 1996

50 Kufeld and others 1981a

53 47 Krysl and others 1984

55 Welch and Pederson 1981a

45 44 50 45 Hickman 1975

51 Wambolt and others 1987a

62 Urness and others 1977

57 51 Striby and others 1987a

65 63 61 Urness and others 1983a

58 50 Wambolt and others 1985a

53 Welch and Wagstaff1992

53 Ward 1971a

59 Nunez-Hernandez and others 1989

68 67 65 67 Pederson and Welch 1982a

59 56 59 54 Mean of all studies

45-68 44–67 50–65 45–67 Range for all studies

a

 Study mean of several values.

maintenance and gestation requirements of most animals but do not meet the lactation needs (tables 4.1

and 4.3). Crude protein levels of big sagebrush are also

fairly stable across seasons with means varying from

11.4 percent for summer and winter to 11.9 percent for

spring and 12.1 percent for fall (table 4.4). Big sagebrush contains enough protein to meet the maintenance, gestation, growth, and lactation requirements

of sheep and cattle year round; maintenance and

gestation of horses; maintenance, gestation, and lactation of deer; and maintenance of birds (tables 4.1 and

4.4). Winter crude protein content levels of big sagebrush seeds could meet the breeding and growing

requirements of birds (tables 4.1 and 4.3). Calcium

levels vary more seasonally than the other nutrients,

reaching a high of 0.72 percent in the spring followed

by a low level of 0.55 percent in the winter with

summer and fall levels intermediate (table 4.5). Only

the calcium requirements of breeding birds, growing

birds, and lactating small mammals are not met by the

winter level of calcium in big sagebrush (tables 4.1 and

4.5). Phosphorus levels of big sagebrush current year’s

growth peaks in the spring and summer at 0.30 to 0.31

percent and declines in the fall to 0.25 percent and

reaches a low level at 0.20 percent in winter (table 4.6).

At the spring and summer levels, big sagebrush could

meet the phosphorus needs for maintenance, gestation, and growth of sheep, cattle, and deer; and maintenance of horses and birds (tables 4.1 and 4.6).

How do nutritive values of big sagebrush compare to

other wildland forage plants? Tables 4.7 and 4.8 give

the answer. Table 4.7 compares the spring in vitro

digestibility, crude protein, phosphorus, and carotene

levels of a number of wildland plants including shrubs,

forbs, and grasses. As a spring forage plant, big sagebrush nutritive value ranks low among the plant

species listed; many are more digestible and contain

higher levels of crude protein, phosphorus, and carotene (table 4.7). It is in the winter when big sagebrush

nutritive value reigns supreme (table 4.8). Winter

current year’s growth of big sagebrush is more digestible than all 22 forage plant species listed; its crude

protein levels are second only to crested wheatgrass

fall regrowth; phosphorus levels are also second only

to crested wheatgrass fall regrowth; and it ranks third

in carotene. It is a very nutritious winter forage that a

number of wildlife species and domestic sheep feed

upon (see chapter II for more details).

Not all big sagebrush subspecies and populations or

accessions within subspecies are equal in digestibility,

levels of crude protein, levels of monoterpenoids, productivity, and preference (see chapter V for more

details). This wealth of variation among big sagebrush

subspecies and populations within subspecies helps

explain some of the differences that occurred among

the various studies conducted on big sagebrush.

For some species of animals such as domestic sheep,

big sagebrush is not a food that they can readily switch

to without a period of slow adjustment. I learned

growing up on a dairy farm that when spring came,

cows were allowed on the green pasture—switching

from dry lot to green pastures—for an hour or two for

the first 3 days, then increased to 3 or 4 hours for the

next 3 days, and then increased to 6 hours for 3 more
112 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 4.5—Calcium content of big sagebrush dry matter by seasons as reported

by various studies.

Spring Summer Fall Winter References

- - - - - - - Percent of dry matter - - - - - - - -

0.25 Cook and others 1951a

0.60 .46 Krysl and others 1984

.24 Elderkin and others 1986a

0.66 .68 Cook and others 1954a

.71 Esplin and others 1937

.72 Goebel and Cook 1960

0.87 .81 .80 .77 Dietz and others 1959

.49 Pederson and Harper 1979

.68 .64 Dietz and others 1962b

.56 .54 .48 .48 Medin and Anderson 1979

.72 .62 .65 .54 Mean of all studies

0.56–0.87 0.49–0.81 0.48–0.80 0.24–0.77 Range for all studies

a

 Study mean of several values.

Table 4.4—Crude protein content of big sagebrush (Artemisia tridentata) dry matter by

seasons as reported by various studies.

Spring Summer Fall Winter References

- - - - - - - Percent of dry matter - - - - - - - -

10.5 Welch and Wagstaff 1992

16 14 14 Urness and others 1983a

10.4 9.1 Krysl and others 1984

8.9 10.0 Williams 1972a

13.4 Elderkin and others 1986a

13 Bayoumi and Smith 1976a

12.4 Welch and McArthur 1979a

13.4 13.6 9.8 10.6 Tueller 1979a

11.6 Bissell and others 1955a

11.0 Smith 1950

9.4 Cook and others 1954a

10.1 Dietz and others 1962aa

11.2 Kinney and Sugihara 1943

11.2 Chemists and Botanist 1906

17.5 Tiedemann and others 1984

8.5 Fajemisin and others 1996

11.9 Nunez-Hernandez and others 1989

10.1 Kufeld and others 1981

12.3 11.2 Dietz and others 1962ba

12.3 Welch 1981

12.0 Pederson and Harper 1979

19.9 13.0 13.5 14.4 Dietz and others 1959

10.5 10.2 10.7 9.7 Bissell and Strong 1955a

7.3 Otsyina and others 1982a

11.7 Goebel and Cook 1960a

10.6 Esplin and others 1937

11.7 Cook and others 1951a

11.9 11.4 12.1 11.4 Mean of all studies

8.9–16.0 8.5–13.6 7.3–17.5 9.1–14.4 Range for all studies

31.1 Kelrick and MacMahon 1985b

28.8 Welch 1999b

a

 Study mean of several values.

b

 Crude protein content of seeds only.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 113

Table 4.7—Spring nutritive values of selected wildland plants (after Welch 1989).

In vitro Crude

Species digestibility protein Phosphorus Carotene

- - - - - - - Percent of dry matter - - - - - - - mg/kg

Shrubs

Antelope bitterbrush 49.1 12.4 0.19 —

Big sagebrush 58.1 12.6 .25 —

Common winterfat — 21.0 — —

Curlleaf mountain mahogany — 9.9 — —

Fourwing saltbush — 14.1 — —

Low rabbitbrush — 22.6 .46 —

Rubber rabbitbrush — 20.7 .45 —

Utah juniper 49.0 6.2 .15 —

Forbs

Alfalfa 86.8 28.5 .37 372.0

American vetch 71.3 21.2 — —

Arrowleaf balsamroot — 28.8 .43 —

Gooseberryleaf globemallow 69.7 19.7 — —

Oneflower helianthella — 20.0 .40 —

Small burnet — 17.4 — —

Grasses

Bluebunch wheatgrass 60.6 17.0 .30 414.0

Bottlebrush squirreltail 72.3 18.5 .24 —

Crested wheatgrass 73.6 23.7 .36 452.0

Fairway wheatgrass 72.6 11.3 — —

Idaho fescue — 14.0 .30 92.0

Indian ricegrass 76.1 15.9 — —

Intermediate wheatgrass 74.3 8.2 — —

Needle-and-thread grass 64.4 12.0 .18 —

Reed canarygrass — 16.2 .40 —

Sandberg bluegrass 62.2 17.3 .33 —

Sand dropseed grass — 15.1 .25 —

Smooth brome — 23.5 .47 493.0

Western wheatgrass 77.2 17.6 .45 185.0

Table 4.6—Phosphorus content of big sagebrush dry matter by seasons as

reported by various studies.

Spring Summer Fall Winter References

- - - - - - - Percent of dry matter - - - - - - - -

0.25 0.29 0.20 0.18 Medin and Anderson 1979

.37 .25 Dietz and others 1962ba

.20 Pederson and Harper 1979

.39 .33 .27 .28 Dietz and others 1959

.23 Goebel and Cook 1960a

.23 Esplin and others 1937

.18 Welch and Wagstaff 1992

.21 .15 Cook and others 1954a

.27 .41 .30 .22 Tueller 1979a

.08 Elderkin and others 1986a

.26 .15 Krysl and others 1984

.24 Cook and others 1951

.30 .31 .25 .20 Mean of all studies

0.25–0.39 0.20–0.43 0.20–0.30 0.08–0.28 Range for all studies

.55 Welch 1999b

a

 Study mean of several values.

b

 Big sagebrush seed only.
114 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

days, and so on, thus slowing switching the diet from

alfalfa hay to green grass and alfalfa. This switching

took place over the course of 10 to14 days. If the switch

was made too quickly, the cow’s milk production would

drop. Johnson and others (1976, p. 278) illustrate this

same principle for big sagebrush when it is force fed to

domestic sheep:

Big sagebrush (Artemisia tridentata) fed to sheep by

stomach pump to study its abortifacient properties

during the 2nd trimester of pregnancy produced no

reproductive difficulties. However, big sagebrush was

lethal when 3/4 lb was fed by this method daily for 1, 2,

or 3 days. Sagebrush fed 1/4 lb daily and slowly increased to 3/4 lb daily was not toxic. These findings

confirm many general reports of suspected sagebrush

toxicity and indicate the need for caution in moving

sheep rapidly onto big sagebrush areas.

The preference rating of the big sagebrush used in the

Johnson and others (1976) study is unknown. Higher

preferred foods are more readily eaten. It is often

speculated that secondary metabolites produced by

big sagebrush are toxic to livestock; however, as

Johnson and others (1976, p. 278) point out: “authoritative evidence of toxicity is scarce.”

Secondary Metabolites ___________

Secondary metabolites are organic compounds that

have no obvious role in the growth and development

of plants but may serve some significant ecological

function or functions, such as essential or volatile oils

that give plants their distinctive odors and flavors,

Table 4.8—Winter nutritive values of selected wildland plants (after Welch 1989)a.

In vitro Crude

Species digestibility protein Phosphorus Carotene

- - - - - - - Percent of dry matter - - - - - - - mg/kg

Shrubs

Antelope bitterbrush 23.5 7.6 0.14 —

Big sagebrush 57.8 11.7 .18 8.0

Black sagebrush 53.7 9.9 .18 8.0

Common winterfat 43.5 10.0 .11 16.8

Curlleaf mountain mahogany 49.1 10.1 — —

Fourwing saltbush 38.3 8.9 — 3.1

Gambel oak 26.6 5.3 — —

Low rabbitbrush 36.0 5.9 .15 —

Rubber rabbitbrush 44.4 7.8 .14 —

True mountain mahogany 26.5 7.8 .13 —

Utah juniper 44.1 6.6 .18 —

Forbs

Arrowleaf balsamroot — 3.6 .06 —

Oneflower helianthella — 2.8 .17 —

Small burnet — 6.6 — —

Grasses

Bluebunch wheatgrass 45.2 3.2 .05 .2

Bottlebrush squirreltail 42.0 4.3 .07 1.1

Crested wheatgrass 43.7 3.5 .07 .2

Crested wheatgrass 50.6 15.0 .39 432.0

 (fall regrowth)

Galleta 48.2 4.6 .08 .4

Idaho fesuce 46.1 3.8 .08 —

Indian ricegrass 50.5 3.1 .06 .4

Needle-and-thread grass 46.6 3.7 .07 .4

Reed canarygrass — 7.8 .14 —

Sandberg bluegrass — 4.2 — —

Sand dropseed grass 53.2 4.1 .07 .5

Smooth brome 47.0 4.1 .12 —

Western wheatgrass 50.2 3.8 .07 .2

a

Data are expressed as a percentage of dry matter, except carotene, which is expressed as mg/

kg of dry matter.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 115

warding off plant pathogens, deterring herbivory, attracting pollinators, and so forth. Secondary metabolites can be classified into five large groups: terpenes,

phenolics, saponins, various glycosides or glucosides,

and alkaloids (Hopkins 1999). Raven and others (1992,

p. 553) observed:

Certain groups of angiosperms have evolved various

secondary products, or secondary metabolites such as

alkaloids, which protect them from most foraging herbivores. However, certain herbivores (normally those

with narrow feeding habits) are able to feed on those

plants and are regularly found associated with them.

Potential competitors are excluded from the same plants

because of their inability to handle the toxins.

In the next section, I will discuss monoterpenoids,

sesquiterpenoids, and certain phenolic compounds produced by big sagebrush and their ecological significance.

Monoterpenoids

Chemistry and Production—Monoterpenoids are

the major constituents of essential or volatile oils in

big sagebrush and are synthesized by way of the

mevalonic acid pathway by “head-to-tail” linkage of

two isoprene units (Buttkus and Bose 1977; Buttkus

and others 1977; Charlwood and Charlwood 1991;

Hopkins 1999; Kelsey and others 1983; Kinney and

others 1941; Nagy and Regelin 1977; Powell 1970;

Sneva and others 1983). These monoterpenoids are 10

carbon units of esters, ethers, aldehydes, alcohols,

ketones; some are known as irregular monoterpenes

(Boyd and Epstein 1976; Buttkus and others1977;

Kinney and others 1941; Powell 1970; Shaw and others 1975). Monoterpenoids are synthesized by epidermal secretory cells of leaves (glandular trichomes) and

are stored in an extracellular cavity surrounded by

cuticle of the epidermis (Hopkins 1999; Kelsey 1982;

Slone and Kelsey 1985). Over 1,000 monoterpenoids,

many from higher plants, have been isolated and

identified (Charlwood and Charlwood 1991).

The monoterpenoids of big sagebrush are a mixture of

various esters, ethers, aldehydes, alcohols, and ketones. Thus far, 33 individual monoterpenoids have

been isolated and identified from the tissues of big

sagebrush (table 4.9). (The reader should not infer that

a given big sagebrush plant population within subspecies or subspecies will contain all monoterpenoids listed.)

Various studies have reported that individual

monoterpenoids isolated from big sagebrush plants

varied from seven to 17, making the composition of

monoterpenoids in big sagebrush tissue among the

most complex in the plant kingdom (Buttkus and others

1977; Kelsey and others 1983; Kinney and others 1941;

McArthur and others 1988; Scholl and others 1977;

Weaver and others 1995; Welch and others 1989).

Weaver and others (1995), studying the chemical composition of volatiles extracted from four plant species—

mountain big sagebrush, wild bergamot (Monarda

fistulosa), arrowleaf balsamroot (Balsamorhiza

sagittata), and sticky geranium (Geranium

viscoissimum)—isolated 11 monoterpenoids from big

sagebrush, eight from wild bergamot, and none from

arrowleaf balsamroot and sticky geranium.

Monoterpenoid levels of big sagebrush differ not

only from a qualitative but also from a quantitative

point among sites or different environmental factors,

seasons, and subspecies and populations within subspecies. Sneva and others (1983, p. 143), studying the

Table 4.9—Monoterpenoids isolated from the tissues of big sagebrush (Buttkus and

others 1977; Kelsey and others 1978,

1983; Kinney and others 1941;

McArthur and others 1988; Shaw and

others 1975; Weaver and others 1995;

Weber and others 1994; Welch and

others 1989).The reader should not

infer that a given big sagebrush plant,

population within subspecies, or subspecies will contain all monoterpenoids

listed.

Artemisia acetate

Artemisia alcohol

Artemisia ketone

Artemisol

Artemiseole

Arthole

Borneol

Camphene

Camphor

Carene

Carvacrol

1,8-Cineole

Cymene

Fenchone

Frenchyl alcohol

Menthol

Methyl santolinate

Myrcene

Ocimene

Ocimeone

Phellandrene

α-Pinene

β-Pinene

Sabinene

Santolina expoxide

Santolina triene

Terpinene

Terpinen-4-ol

Terpineol

α-Thujone

β-Thujone

Thujyl alcohol

Yomogi alcohol
116 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

effects of nitrogen fertilization on the essential oil

production of Wyoming and mountain big sagebrush,

observed: “No significant effects were found due to large

variation in oil levels between plants within a fertilizer

treatment. A tendency for lower oil concentration in

fertilized mountain and Wyoming big sagebrush was

evident, whereas levels of oil in low sagebrush were

almost nil, regardless of treatment.” Kelsey (1986a)

reported similar results for the production of crude

terpenoids. Powell (1970) reported, based on a study of

39 plots with a wide range of vegetative, physiographic,

and soil factors, that volatile oil content of big sagebrush was positively and significantly correlated with

effective rooting depth, phosphate in the A horizon,

nitrogen in the 6- to 12-inch layer of soil, clay content

in the upper 6 inches of soil, and big sagebrush plant

size. Each of these factors reflects an increase in oil

content with an increase in the favorableness of growing conditions for big sagebrush. Factors that seem to

reduce oil content were clay content in the effective

rooting depth, potassium, and magnesium in the A

horizon, and favorable water relationships. However,

there may be a problem with the Powell (1970) study.

In all likelihood, he was working with different subspecies of big sagebrush; thus, genetic factors were not

kept constant throughout the 39 study plots, which

would in turn confound the results. The effects of

environmental factors on big sagebrush monoterpenoid

production are therefore most likely confounded by

subspecific variation.

Seasonal concentration of monoterpenoids in big

sagebrush leaf and stem tissues varies independently

of genetic and environmental factors. Kelsey and others (1982) noted that monoterpenoid levels were lowest during the spring and increased through the summer until reaching peak levels in the fall (September)

and then decreased to intermediate levels in the winter. A study conducted by Cedarleaf and others (1983)

agrees with the general trend of the Kelsey and others

(1982) study, but peak monoterpenoid levels occurred

in the summer months of July and August. The Kelsey

and others (1982) study did not sample big sagebrush

tissues in July or August. Both studies noted differences in the levels of monoterpenoids for subspecies

and populations within subspecies.

Welch and McArthur (1981) offer the strongest proof

that the production of monoterpenoids is under strong

genetic control. They studied the variation of

monoterpenoid content among subspecies and populations within subspecies of big sagebrush plants grown in

a common or uniform garden; or in others words, with

environmental factors held constant. They reported significant differences among subspecies and populations.

The Monoterpenoid Controversy—Monoterpenoids

have bacteriostatic and bactericidal properties (Nagy

and Regelin 1977; Nicholas 1973). Microbiologists

have investigated these compounds in determining

their usefulness as prophylactic agents. With the

discovery of antibiotics, the interest in using

monoterpenoids to prevent or ward off bacterial infections died. Because of the antimicrobial nature of

monoterpenoids, researchers in the 1960s and 1970s

and even to the 1990s became concerned about the

possible adverse effects monoterpenoid-producing

plants such as big sagebrush might have on ruminant

and fecal microorganisms’ cellulolytic digestive abilities (Dietz and Nagy 1976; Hobbs and others 1986;

Nagy 1979; Nagy and others 1964; Nagy and Tengerdy

1967, 1968; Ngugi and others 1995; Wallmo and others

1977; Wallmo and Regelin 1981). Dietz and Nagy

(1976) suggested that the “theoretical” decline of mule

deer in the Western United States was due principally

to undue dependence on big sagebrush, juniper

(Juniperus ssp.), pine (Pinus ssp.), and other species

that contain high levels of monoterpenoids. They labeled monoterpenoids as toxic materials. Further,

Nagy (1979) reported that during a 30-day winter

grazing trial, deer experienced considerable weight

loss and some became ill at the peak of big sagebrush

consumption. Carpenter and others (1979) found, however, during a 30-day winter grazing trial with six

mule deer, that at the peak of big sagebrush consumption, three deer were gaining weight and two deer were

maintaining their weight. The sixth deer lost weight

throughout the entire study. Wallmo and others (1977),

embracing the in vitro evidence that big sagebrush

monoterpenoids are toxic to rumen microorganisms,

describe an inescapable nutritional dilemma that faces

wintering mule deer. The dilemma centers on the need

of wintering mule deer to extract 7 percent crude

protein from forages with an average crude protein

content of 5 percent. To increase protein intake, deer

would need to consume more of the highly lignified

browse twigs or more big sagebrush along with its

toxic monoterpenoids, thereby lowering total digestibility. To increase digestibility, deer would need to eat

more grass, which in turn would lower protein intake.

These ideas about the adverse effects of big sagebrush monoterpenoids on digestion do not agree with

the in vitro digestibility data reported in table 4.8 that

big sagebrush is among the most digestible winter

forage listed (Welch and others 1982). Wallmo and

others (1977), however, pointed out that the preparatory techniques used could have caused large losses of

monoterpenoids from the big sagebrush samples, thus

introducing bias. The in vitro digestion trials conducted by Welch and Pederson (1981) were designed to

overcome the loss of monoterpenoids during the preparatory step. They did this by grinding the samples

in liquid nitrogen with a steel motorized mortar and

pestle. The results of their study showed that big

sagebrush is a highly digestible browse (also see
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 117

supporting studies by Striby and others 1987; Wambolt

and others 1985, 1987).

Additional evidence that a high level of big sagebrush in the diet of mule deer does not adversely affect

digestion comes from a study conducted by Tueller

(1979). He reported that the diet of mule deer wintering in the Fox Mountain area of Nevada was 69

percent big sagebrush, whereas the diet of the White

Rock herd was 28 percent. While the amount of big

sagebrush in the diet of the deer from the two areas

differed by a factor of 2.5, the percentage of tail fat (an

indicator of body condition) was almost the same for

the two deer herds: Fox Mountain 32.4 percent and

White Rock 29.1 percent. It should be noted that 69

percent big sagebrush in the diet of the Fox Mountain

deer herd is 2.3 to 4.6 times the level considered safe

by some workers (Nagy and others 1964; Wallmo and

others 1977; Wallmo and Regelin 1981).

The conflict between the digestion data of table 4.8

and the reports of Striby and others (1987), Tueller

(1979), Wambolt and others (1985, 1987), and Welch

and Pederson (1981), on one side, and the studies of

Ngugi and others (1995), Nagy and others (1964),

Wallmo and others (1977), and Wallmo and Regelin

(1981) on the other side, can be explained. Two options

seem apparent: (1) microorganisms can adapt to the

presence of monoterpenoids, or (2) the host animal can

reduce concentration of monoterpenoids in the rumen

below levels toxic to the microorganisms (Welch 1983,

1993). Nagy and Tengerdy (1968, p. 441) observed:

Rumen microorganisms of wild and captive deer were

subjected to increasing amounts of volatile oils. The oils

had a marked antibacterial effect on the rumen bacteria when the concentration reached approximately 16

uliter of oil per 10 ml of rumen fluid nutrient broth. The

gross reactions of rumen bacteria obtained from wild,

as well as captive, deer to the volatile oils seemed to be

of the same magnitude; thus no adaptation by the

bacteria to the oils was apparent.

The data presented in table 1 of the Nagy and

Tengerdy (1968) study do not support their conclusion.

The rumen inoculum exposed to big sagebrush

monoterpenoids, that is wild deer, showed signs of

being more tolerant of the presence of monoterpenoids

than the rumen inoculum not exposed, that is the tame

deer. For instance, at an oil (monoterpenoid) concentration of 18 ul per 10 ml of culture medium, the wild

deer inoculum contained 6.67 x 108 bacterial survivors

per ml of culture medium compared to 5.77 x 104 for the

tame deer inoculum. In other words, the deer consuming big sagebrush (wild deer) had 11,715 times more

bacterial survivors per ml of culture medium than did

tame deer that did not consume big sagebrush. This is

strong evidence of adaptation. However, Pederson and

Welch (1982) reported that inocula from mule deer not

previously exposed to big sagebrush or any other

monoterpenoid-producing plant species digested all

test forages, including big sagebrush, equally as well

as inoculum from deer that had been exposed to big

sagebrush monoterpenoids. They concluded that rumen microorganisms do not have to adjust to the

presence of the monoterpenoids.

During in vitro digestion trials conducted by Welch

and Pederson (1981), they wanted to know what was

happening to the monoterpenoids during the digestibility trial. Therefore, they modified the digestibility

trial by adding three digestive tubes that contained

only buffer. To these tubes, they added specific amounts

of pinene and camphor, and after the first incubation

period the solutions in the tubes were extracted with

absolute ether. Gas chromotography was used to detect any changes in the monoterpenoid content. None

of the pinene was recovered; all was lost from the

tubes, and 17.3 percent of the camphor was lost. A

white condensate had formed a ring around the neck

of the tubes. Each ring was located about 70 mm above

the surface of the digestion solution; the condensate

was identified as camphor. The force that drove these

compounds out of the digestion solution was heat.

Apparently, 38.5 °C, which is close to the normal body

temperature of mule deer, is sufficient to volatilize the

monoterpenoids. From this observation, Welch and

Pederson (1981) hypothesized that monoterpenoid

levels could be greatly reduced in the rumen in three

ways: (1) through mastication and rumination, (2) volatilization by body heat and eructation, and (3) possible

absorption through the rumen wall and excretion

through the kidneys.

This hypothesis was tested by Cluff and others

(1982) with wild mule deer and by White and others

(1982) with pygmy rabbits (Brachylagus idahoensis).

They found monoterpenoid levels in the rumens of

mule deer or the stomachs of pygmy rabbits were only

20 to 23 percent of expected levels. This large loss of

monoterpenoids from ingested forage has been observed in other species including sage grouse

(Centrocercus urophasianus), greater glider (Petauroides

volans), and brushtail possum (Trichosurus vulpecula)

(Foley and others 1987; Welch and others 1989). This

large loss of monoterpenoids resolves the conflict between

in vitro evidence that big sagebrush monoterpenoids

inhibit rumen microorganisms and digestive trials

that show that big sagebrush is a highly digestible

winter forage.

A study concerning the influence of crude terpenoid

on in vitro digestion among taxa of big sagebrush and

black sagebrush by Striby and others (1987) deserves

special attention. Crude terpenoid is defined as the

compounds that are extracted from the glandular

trichomes of leaves using batch extraction for 5 minutes in chloroform. This would remove not only the

monoterpenoid but also other terpenoids, waxes, and

other chloroform soluble compounds. Striby and others
118 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

(1987) found that intact big sagebrush tissues that are

not extracted with chloroform were a highly digested

food. But digestibility could be increased 12.3 percent

by removing the crude terpenoid faction from big

sagebrush. Unfortunately, the authors were not able

to determine if the increase was due to the removal of

monoterpenoids, or other kinds of terpenoids, or waxes,

and so forth. They did note that the taxon with the

highest crude terpenoid content was also the same

taxon with the highest intact digestibility. This data,

again, suggest little negative impact of any terpenoids

on digestion of big sagebrush tissues.

During digestibility trials, Smith (1950) noted that

deer showed definite aversion to individual big sagebrush plants. This preference of mule deer for certain

subspecies, populations within subspecies, and individual plants has been observed in the field by a

number of researchers (Hanks and others 1971;

McArthur and others 1979; Scholl and others 1977;

Sheehy and Winward 1981; Stevens and McArthur

1974; Wambolt 1996, 2001; Wambolt and others 1987;

Welch and others 1981; Willms and others 1979).

Nagy and Tengerdy (1968) and Dietz and Nagy

(1976) hypothesized that black sagebrush (Artemisia

nova) is preferred over big sagebrush by mule deer

because black sagebrush contains lower concentrations of monoterpenoids than does big sagebrush.

Observations made by Smith (1950) and Sheehy and

Winward (1981), however, showed that mule deer

preferred big sagebrush over black sagebrush even

though monoterpenoid content of black sagebrush was

lower than big sagebrush. Mule deer preference for

populations of black sagebrush grown on a uniform

garden that is grown under similar environmental

conditions varied, and the levels of monoterpenoids

also varied (Behan and Welch 1985; Scholl and others

1977; Welch and others 1983). Behan and Welch

(1985) pointed out that a population of black sagebrush from Pine Valley Ridge, UT, was preferred by

wintering mule deer over six other populations, but

monoterpenoid content was not related to preference.

In an earlier study conducted on the same uniform

garden, Welch and others (1983) reported the percentage of current year’s growth consumed by mule deer

for a population of big sagebrush collected from the

mouth of Hobble Creek Canyon near Springville, UT,

was 83 percent or almost the same use as the Pine

Valley Ridge at 82.7 percent (Behan and Welch 1985).

While the use of the two taxa was the same, the

monoterpenoid concentration was not. Total

monoterpenoid content for the Hobble Creek big sagebrush population was 2.21 percent of dry matter, and

concentration for the black sagebrush was 0.63 percent of dry matter; or in other words, Hobble Creek big

sagebrush contained 3.5 times more monoterpenoids

than did the black sagebrush, but both were equally

used.

Welch and Wagstaff (1992, p.140) observed that

“‘Hobble Creek’ mountain big sagebrush, a

monoterpenoid producing shrub, was preferred by

wintering mule deer over a non-monoterpenoid shrub

antelope bitterbrush.” In addition, Welch and Andrus

(1977, p. 5), who were studying the value of rose hips

as a winter food for mule deer, noted: “Mule deer prefer

rose hips over black chokecherry and antelope bitterbrush but not Vasey big sagebrush.” Leach (1956, p.

279), studying food habits of the Great Basin deer

herds of California, found that the high use of big

sagebrush “could not always be attributed to the

unavailability of bitterbrush forage,” or in other words,

deer in his study consumed big sagebrush by choice.

Remington and Braun (1985) concluded from their

study that subspecies Wyoming big sagebrush was

preferred by wintering sage grouse over subspecies

mountain big sagebrush. Remington and Braun (1985,

p. 1055) stated: “Mountain big sagebrush (ATV) is

common in drawbottoms and on east facing slopes

where snow accumulates. Wyoming big sagebrush

(ATW) is common on drier sites including ridge tops

and benches or in alkaline areas in association with

black greasewood (Sarcobatus vermiculatus) and alkali sagebrush (AL).”

Is there a problem with equal access (Welch and

others 1991)? Are mountain big sagebrush plants

growing in drawbottoms as accessible to wintering

sage grouse as Wyoming big sagebrush plants growing

on ridgetops, benches, and so forth? If not, then utilization and chemical comparisons between subspecies

would be biased toward accessibility and bird behavior

and not preference. Comparisons within subspecies

were meaningful. Remington and Braun (1985) found

that browsed, unbrowsed, and random Wyoming big

sagebrush samples of leaves differ in the amount of

crude protein and that sage grouse seem to select

plants with leaves containing higher crude protein

levels but similar levels of monoterpenoids. For mountain big sagebrush, sage grouse also selected plants

with higher concentrations of crude protein but containing lesser amounts of three of 15 monoterpenoids.

Again, we have some evidence that monoterpenoids do

not influence preference for browsing on big sagebrush

and some evidence that monoterpenoids do influence

preference; however, the choice the sage grouse were

making was among monoterpenoid-producing big sagebrush plants and not monoterpenoid plants versus

nonmonoterpenoid plants.

Personius and others (1987, p. 87) studying the

influence of crude terpenoid on mule deer preference

for sagebrush concluded:

Determining the importance of sagebrush epidermal

chemicals as mediators of herbivory requires further
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 119

investigation. There are numerous variables. Little

information is available on chemical potencies and

threshold levels for individual compounds. Carefully

controlled feeding trials are necessary to clearly evaluate the effects of specific sagebrush chemicals on the

feeding behavior of mule deer and other herbivores.

However, Kelsey (1986b, p. 385) claims: “Epidermal

chemicals of sagebrush appear to function as a defense

against herbivores.” He also noted that defoliation of

sagebrush plants failed to produce higher concentrations of these defense chemicals as a means of providing additional protection, like described by Bryant

(1981) for snowshoe hare. Later, Bryant and others

(1992, p. 18), concerning the protection of plants by

secondary metabolites, noted: “Herbivory by mammals also affects the chemical defenses of woody plants.

In some cases browsing results in increased defense

and in others decreased defense.” The role of secondary metabolites in determining preference of animals

for subspecies, populations within subspecies, and

individuals within populations of big sagebrush appears to create more controversy than enlightenment.

Weber and others (1994, p. 689) noted: “Several

studies have shown that high levels or composition of

monoterpenoids reduce rumen microbial activity of

browsing species and affect palatability of A. tridentata

(Longhurst et al., 1969; Personius et al., 1987; Bray et

al., 1991).” This statement needs special comment.

What does “several studies” mean? Do high levels

mean levels normally found in big sagebrush tissues?

They cited three references to support their statement, but only one (Longhurst and others 1969) was

concerned with digestibility. The Personius and others (1987) and Bray and others (1991) studies, contradictory in nature, were concerned with preference and

monoterpenoids. Effects or lack thereof of

monoterpenoids on digestion has been discussed in the

previous section. Personius and others (1987) clearly

show that wintering mule deer preferred mountain

big sagebrush over all other sagebrush taxa studied

(see their table 1). Mountain big sagebrush contained

greater concentrations of 1,8-cineole, a monoterpenoid,

than the other taxa by a factor ranging from 3.4 to 27.5

(see their table 2). 1,8-cineole in this case could be

called a preference “attractant.” But Bray and others

(1991) found 1,8-cineole to be the strongest preference

“deterrence” of all the compounds tested. McLean and

others (2001, p. 1078) observed: “most mammalian

herbivores ingest large concentrations of many PSMs

(plant secondary metabolites) that do not appear to

have major effects on their choices of foods.” These last

three references do not lend much support to the

statement of Weber and others (1994).

Methyl Jasmonate

Methyl jasmonate—a volatile substance from big

sagebrush and other plants and a common perfume

ingredient—has the ability to induce antiinsect compounds called “proteinase inhibitors” in other plant

species. Farmer and Ryan (1990) demonstrated that

when big sagebrush leaves and stems are incubated

with tomato plants, proteinase inhibitors are induced

in tomato plants. These inhibitors interfere with the

normal metabolism of protein inside the insect, resulting in growth irregularities and death (Chen 1990).

Farmer and Ryan (1990, p. 7713) maintained that

their study demonstrated “interplant communication

can occur from leaves of one species to leaves on

another species to activate the expression of defensive

genes.” Karban and others (2000) and Karban (2001)

reported that wild tobacco (Nicotiana attenuata) plants

became more resistant to herbivores when near clipped

big sagebrush plants. The basis of this resistance

appears to be an increase in the activity of polyphenol

oxidase in the tobacco plants.

Sesquiterpenoids

Sesquiterpenoids are 15 carbon unit compounds

that form the largest class of terpenoids and commonly

occur with the monoterpenoids in essential oils but in

lower concentrations (Bramley 1997). They, like the

monoterpenoids, are manufactured in glandular trichomes (Kelsey 1982). Thousands of these compounds

have been isolated and identified and more than 100

sesquiterpenoids skeletons are known. They form acyclic, monocyclic, bicyclic, and tricyclic molecules with

a variety of functional groups. These compounds are

responsible for a number of biological, ecological, and

pharmacological activities including antimicrobial

properties, growth regulators, insect hormones, insect

pheromones, phytoalexins, antioxidants, organoleptic

properties, antitumour, antiinflammatories,

antihyperlipidemic properties, antiulcer, expectorant,

sedative, analgesic properties, allelopathy, antifeedant,

and so forth (Bramley 1997). Sesquiterpenoid lactones

are the largest group of sesquiterpenoids; over 3,000

naturally occurring compounds are known. They have

been studied in terms of chemotaxonomy and for

delineation of phylogenetic relationships among closely

related plant groups.

Sesquiterpenoid lactones have received some attention as an aide in understanding the phylogenetic

relationships among the various groups of big sagebrush and other sagebrushes (Bhadane and others

1975; Geissman and others 1967; Irwin and others

1969; Kelsey and others 1973; Shafizadeh and Bhadane

1973; Shafizadeh and others 1971). To date 24

sesquiterpenoid lactones have been isolated and identified from big sagebrush (table 4.10; Kelsey and

Shafizadeh 1979). The biological and ecological significance of these compounds of big sagebrush has not

been determined. However, Kelsey and Shafizadeh

(1979) concluded that the chemical data from
120 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 4.10—Sesquiterpenoids isolated from the tissues of big sagebrush (Bhadane and

others 1975;Geissman and others 1967;

Irwin and others 1969; Kelsey and others

1973; Kelsey and Shafizadeh 1979;

Shafizadeh and Bhadane 1973;

Shafizadeh and others 1971).The reader

should not infer that a given big sagebrush plant, population within subspecies, or subspecies will contain all

sesquiterpenoids listed.

Arbusculin-A

Arbusculin-B

Arbusculin-C

Artevasin

Badgerin

Deacetoxymatricarin

Deacetyllaurenobiolide

Deacetylmatricarin

Dehydroleucodin

Dentatin-A

Dentatin-B

Isophotosantonic lactone

Parishin-A

Parishin-B

Parishin-C

Ridentin

Rothin-A

Rothin-B

Spiciformin

Tatridin -A

Tatridin-B

Tatridin-C

W-A

W-B

sesquiterpenoid lactones studies suggest that big sagebrush developed from a North American ancestral line

rather than Old World lines.

Phenolic Compounds

The basic structural unit of phenolic compounds is

an aromatic ring (a ring of six carbons with three

double bonds) to which a hydroxyl group is attached

(—OH). From this simple structure a large and chemically diverse family of chemicals arises that are universally present in plants and in all plant parts. Raven

and others (1999, p. 34) observed: “Although they

represent the most studied of secondary metabolites,

the function of many phenolic compounds is still unknown.” They range from simple phenolic acids to

large and complex polymers such as tannins and

lignin; also included in this family of compounds are

flavonoids and coumarins. All are products via the

shikimic acid pathway.

Table 4.11 lists 13 to14 (the exact number is uncertain because of potential spelling differences among

studies for possibly the same compounds) coumarins

and 10 flavonoids that have been isolated and identified. The biological and ecological significance of these

substances has not been established. They were used

in an attempt to understand the phylogenetic relationship among closely related groups of sagebrush.

Allelopathy _____________________

Allelopathy is chemical warfare among plants, among

animals, and even between plants and microorganisms,

or other such relationships. Originally, the term allelopathy encompassed all inhibitory and stimulatory

Table 4.11—Coumarins and flavonoids isolated from

the tissues of big sagebrush (Brown

and others 1975; Rodriguez and others 1972; Shafizadeh and Melnikoff

1970; Tamma and others 1985; Wilt

and Miller 1992; Wilt and others

1992).The reader should not infer that

a given big sagebrush plant, population within subspecies, or subspecies

will contain all coumarins or flavonoids

listed.

Coumarins

Aesculetin

Aesculin

Artelin

Cichoriin

Esculetin

Esculin

Isoscopoletin

Methylaesculina

Methylesculina

Scoparon

Scoparone

Scopoletin

Skimmin

Umbelliferone

Flavonoids

Apigenin-7-0-glucoside

Axillarin

Cupafolin

Eupafolin

Kaempferol

Luteolin

Luteolin-7-glucoside

Penduletin

Quercetagetin

Quercetin

a Question as to whether these compounds are different

or difference in spelling for the same compound.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 121

interactions, but the term was derived from the Greek

words allelon (each other) and pathos (to suffer) and

should mean injurious effects of one on another (Friedman 1995; Kelsey and Everett 1995). Many plantderived chemicals phytochemicals stimulate plant

growth and development at low levels, but are inhibitors at high levels (Friedman 1995; Kelsey and Everett

1995). As with Kelsey and Everett (1995), I will restrict the term allelopathy in this presentation to

inhibitory effects.

The reader needs a clear understanding of the difference between allelopathic relationships among plants

living together, and competitive relationships. Kelsey

and Everett (1995, p.481) explain the difference:

When two or more species live together they may

interfere with each other. This interference can have

positive, negative, or neutral effect on the fitness of

each species. Competition occurs when there is a limited resource, or resources, in an environment where

species are interacting. The result is negative interference because the interacting species will be less successful in the presence of a competitor than they would

have been if growing alone in the limiting environment.

Allelopathy differs from competition in its mode of

action and its effect on species interactions. Allelopathy

functions through the addition of phytochemicals to the

environment by one of the interacting species, thereby

resulting in the inhibition of its neighbor sharing the

habitat simultaneously or sequentially (Fuerst and

Putnam 1983). In this situation, the fitness of the

phytochemical donor species remains unchanged relative to its growth alone, whereas the recipient species,

suffering from growth inhibition, will be less successful

because of the reduced fitness or negative interference.

Most allelopathy research has been conducted under controlled or semicontrolled environments of the

laboratory or greenhouse (Friedman 1995). To determine the allelopathic effects of a plant, germinating

seeds are exposed to whole plant, specific plant parts

(seeds, shoots, roots, and so forth), plant extracts, or to

a specific phytochemical produced by the “aggressive”

species (Friedman 1995). Plant species showing an

allelopathic reaction under laboratory (Rychert and

Skujins 1974) or greenhouse environments to

phytochemicals (terpenoids, phenolics) of big sagebrush are listed in table 4.12. Not included in the

listing are blue-green algae-lichen crusts (Rychert

and Skujins 1974).

Rychert and Skujins (1974), using laboratory techniques, found that aqueous extracts from big sagebrush leaves inhibit nitrogen fixation or acetylene

reduction of the blue-green algae (now called

cyanobacteria) lichen crusts, thus providing evidence

of possibly allelopathic effects. Kelsey and Everett

(1995) suggest that litter of big sagebrush may have

the same inhibitory effects.

Yet five reports claim that soil nitrogen levels under

big sagebrush plants are higher than in the interspace

between plants (Charley 1977; Charley and West

1975, 1977; Fairchild and Brotherson 1980; Wikeem

and Pitt 1982). Charley and West (1977) reported total

and nitrate nitrogen levels under big sagebrush canopy

to be significantly higher—almost twice that of the

interspaces. If the secondary metabolites of big sagebrush are inhibiting nitrogen fixation, how does one

explain the results of these five studies? Perhaps

Kelsey and Everett (1995, p. 482) offer a clue: “Because

of the experimental difficulties and the complexity of

biotic and abiotic factors influencing natural interactions, not all ecologists and biologists are convinced

that allelopathy is a significant ecological phenomena

in natural environments.” Inderjit and Weston (2000)

agree.

Hoffman and Hazlett (1977, p. 137) observed: “In our

experiments the germination of Parietaria pensylvanica, Euphorbia podperae, Hedeoma hispida, and

Achillea millefolium was inhibited by litter extracts of

Artemisia tridentata. Yet, in the field, these same

species are most abundant directly under or very near

A. tridentata shrubs.” Further Hoffman and Hazlett

(1977, p. 137) stated: “It is important to point out that

most plant-plant interactions are not simple one factor interactions. A plant is influenced by a multiplicity

of environmental factors.” Krannitz and Caldwell

(1995, p. 166), studying root growth responses of two

grass species when their roots came into contact with

mountain big sagebrush roots, observed: “Contrary to

expectations, when roots of any test species contacted,

or were in the vicinity of, Artemisia roots, their growth

rate was not significantly affected.” This “contrary to

expectations” statement demonstrates the long held

belief that big sagebrush possess allelopathic powers

over other range plants.

To counter this preconceived idea, I add my personal

observations. In 1989, I established a big sagebrush

seed increase garden at the Point of the Mountain just

west of the Utah State Prison and south of Salt Lake

City. For 5 years I kept this garden nearly weed free

until 1994 when general weed control was no longer

practiced; however, weeds under the canopy of the big

sagebrush plants were removed by use of needle nose

pliers. During spring of 1999, a list of species was

generated that had germinated in the fall of 1998 or

spring of 1999 under the canopy of established big

sagebrush plants. Seedlings of species so found were:

big sagebrush, cheatgrass (Bromus tectorum), common mallow (Malva neglecta), dalmatian toadflax

(Linaria genistifolia), Kentucky bluegrass (Poa

pratensis), needle-and-thread grass (Stipa comata),

prickly lettuce (Lactuca serriola), puncturevine

(Tribulus terrestris), rubber rabbitbrush (Chrysothamnus nauseosus), red root pigweed (Amaranthus

retroflexus), Russian thistle (Salsola pestifer), rye

(Secale cereale), tumble mustard (Sisymbrium

altissimum), flixweed (Descurainia sophis), western
122 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

salsify (Tragopogon dubius), and yellow sweetclover

(Melilotus officinalis). All these species had germinated under the canopy of 9-year-old big sagebrush

plants whose litter had not been disturbed for at least

4 years. These personal observations do not support

the contention that big sagebrush is an agent of

allelopathy.

In 1990, I established a garden of mixed species at the

Point of the Mountain. Species planted were antelope

bitterbrush (Purshia tridentata), black sagebrush, big

sagebrush, firecracker penstemon (Penstemon eatonii),

Gambel oak (Quercus gambelii), Indian ricegrass

(Oryzopsis hymenoides), scarlet globemallow

(Sphaeralcea coccinea), and rubber rabbitbrush. This

Table 4.12—Species showing allelopathic effects under laboratory or green

house conditions to big sagebrush chemicals (Groves and

Anderson 1981; Hoffman and Hazlett 1977; Kelsey and others

1978; Klarich and Weaver 1973; McCahon and others 1973;

Reid and others 1963; Schlatterer and Tisdale 1969; Weaver

and Klarich 1977; Wilkie and Reid 1964).

Common name Scientific name

Alfalfa Medicago sativa

Barley Hordeum vulgare

Bean Phaseolus vulgaris

Bottlebrush squirreltail grass Sitanion hystrix

Bluebunch wheatgrass Agropyron spicatum

Canada bluegrass Poa compressa

Creeping juniper Juniperus horizontalis

Crested wheatgrass Agropyron desertorum

Corn Zea mays

Cucumber Cucumis sativus

Douglas-fir Pseudotsuga menziesii

— Echinacea pallida

Englemann spruce Picea engelmannii

— Euphorbia podperae

Fairway wheatgrass Agropyron cristatum

Field pennycress Thlaspi arvense

— Hedeoma hispida

Giant wild rye Elymus cinereus

Idaho fescue Festuca idahoensis

Indian ricegrass Oryzopsis hymenoides

Ironplant goldenweed Haplopappus spinulosus

Limber pine Pinus flexilis

Lodgepole pine Pinus contorta

Mountain big sagebrush Artemisia tridentata spp. vaseyana

Pennsylvania pellitory Parieteria pennsylvanica

Ponderosa pine Pinus ponderosa

Prairie sandgrass Calamovilfa longifolia

Oat Avena sativa

Radish Raphanus sativus

Rocky Mountain juniper Juniperus scopulorum

Rubber rabbitbrush Chrysothamnus nauseosus

Slender wheatgrass Agropyron trachycaulum

Silver sage Artemisia cana

Smooth brome Bromus inermis

Subalpine fir Abies lasiocarpa

Sunflower Helianthus annuus

Thickspike wheatgrass Agropyron dasystachyum

Thurber needlegrass Stipa thurberiana

Western yarrow Achillea millefolium

Western wheatgrass Agropyron smithii

Wheat Triticum aestivum

White spruce Picea glauca

Wooly plantain Plantago patagonica
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 123

garden was also kept weed free by means of a hoe,

except under the developing canopy of the big sagebrush plants. Here weed control was achieved by hand

pulling small weed plants with needle nose pliers,

thus minimizing disturbance to the buildup of litter

under the big sagebrush plants. At the beginning of

the 10th growing season a list of plant species that had

germinated under the big sagebrush canopy during the

spring of 1999 was made. Species found included those

listed for the 1989 garden, but additional species were

found: firecracker penstemon, desert paintbrush

(Castilleja chromosa), and Indian ricegrass (fig. 4.1).

Again, these personal observations do not support the

contention that big sagebrush is an agent of allelopathy.

In addition to these garden observations, I have

found in the field the seedlings of bigtooth maple (Acer

grandidentatum), box elder (Acer negundo), singleleaf

pinyon pine (Pinus monophylla), and Utah juniper

(Juniperus osteosperma) growing under the canopy of

mature big sagebrush plants.

Diettert (1938, p. 5) observed: “Not only is [big

sagebrush] of direct value as a forage crop but in many

places it provides shelter for tender and perhaps more

useful plants.” Drivas and Everett (1987, 1988),

Callaway and others (1996), and Chambers (2001)

describe the use of big sagebrush as nurse plants for

singleaf pinyon (Pinus monophylla) seedlings, Patten

(1969) for lodgepole pine (Pinus contorta), and Schultz

and others (1996) for curlleaf mountain mahogany

Figure 4.1—Four plant species (firecracker penstemon, Penstemon eatonii; Indian ricegrass, Oryzopsis

hymenoides; common mallow, Malva neglecta; tumble mustard, Sisymbrium altissimun) germinated under the

litter and canopy of a mature big sagebrush (Artemisia tridentata) plant (photo by Bruce L. Welch).

(Cercocarpus ledifolius). Also in the field, I have noticed at various locations that the only grasses and

forbs present on a site were to be found under the

canopy of big sagebrush plants (also see Weaver and

Albertson 1956). Figure 4.2 illustrates this point. This

photograph was taken at the Benmore Experimental

Range just south of Vernon, UT, where pastures of

crested wheatgrass were established to determine

how much grazing pressure the grass could tolerate.

The increase in bare ground in the picture was due to

grazing, not to increasing big sagebrush canopy as

hypothesized by Baxter (1996).

Blaisdell (1953, p. 1) observed: “Even when livestock

force their way into heavy [big] sagebrush stands, they

are often unable to reach more than half of the palatable grasses and forbs.” In other words, big sagebrush

canopy form a protective barrier (Costello 1944; Weaver

and Albertson 1956). How then, can big sagebrush be

both a protector of grasses and forbs and an agent of

allelopathy?

Daubenmire (1975, p. 31) states: “Field observations

in Washington indicate that not only is there no

allelopathic influence from the species of Artemisia,

but that it has a beneficial effect on other plants.”

Wight and others (1992) describe a “beneficial effect on

other plants” as being in the area of water conservation (Chambers 2001) and extending water near the

soil surface by 2 weeks versus interspaces between

plants. They noted that big sagebrush canopies reduce
124 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

solar radiation and prolong the period favorable for

seedling establishment for perhaps as long as 28 days

(also see Chambers 2001; Pierson and Wight 1991; for

favorable soil temperatures under big sagebrush).

Hazlett and Hoffman (1975) studied the pattern of

plant species placement in relation to big sagebrush

distribution in western North Dakota. Their study site

was dominated by big sagebrush, which had a cover

value of 29 percent. They counted the number of

established plants found in three concentric zones

under and beyond the individual big sagebrush plant

canopies. The number of established plants in the

inner zone (zone 1), which is directly beneath the

canopies, greatly exceeded the number of plants (most

forbs—18 species) of the two outer most zones (3,145

for zone 1; 1,845 for zone 2; and 325 plants for zone 3).

However, they felt that grass cover was greater in the

outer zone. Eckeret and others (1986) reported similar

results.

Even experts such as Kelsey and Everett (1995, p.

518) have questions: “Can volatile terpenes adsorbed

on soil particles the previous summer and fall, or

leached during the winter, remain at toxic levels until

spring germination? Does sagebrush litter, in spring,

have sufficient concentrations of toxins to interfere

with growth? What happens to the large quantities of

sesquiterpene lactones in the foliage of sagebrush?

Are they ever inhibitory?” Evidence suggests that

allelopathy of big sagebrush is more myth than fact

(Caldwell 1979; Daubenmire 1975; Peterson 1995).

Issue of Bare Ground Cover and

Grass Cover ____________________

There is an untested hypothesis that states: the

surface roots of big sagebrush roots in the interspaces

among big sagebrush plants have the capacity to

capture water and nutrients to the point that they

starve out associated herbaceous plant species. Because of this untested hypothesis and the alleged

allelopathic properties of big sagebrush, some workers

claim that when big sagebrush canopy cover exceeds

15 percent (12 to 20 percent), bare ground cover will

increase while grass production and/or cover will decrease (Baxter 1996; Winward 1991). Let us examine

this issue.

Big Sagebrush Cover Versus Bare Ground

Cover

The relationship between big sagebrush canopy cover

and the percent of bare ground can be seen in table

4.13. Data in this table were collected during the 1998

Utah big game range trend studies and published by

the Utah Department of Natural Resources, Division

of Wildlife Resources (Davis and others 1999). I chose

only those study sites where big sagebrush canopy

cover exceeded all other shrub species present on the

sites. Subspecies of big sagebrush present on a given

site is listed in the table. Percent of big sagebrush

canopy cover ranged from 3 to 24 percent. In 12 of the

26 sites selected, cover exceeded the recommended

limits set by Baxter (1996). Correlation coefficient for

this data set was r = –0.2592, and coefficient of determination was R2 = 0.07. Neither value is significant.

Calculating r and R2 for the 12 sites where big sagebrush canopy cover was 15 percent or greater, r was +

0.02 with R2 = 0.0003; or, in other words, there is no

significant relationship between big sagebrush canopy

cover and bare ground. Other studies present data

containing big sagebrush canopy cover and bare ground,

which show the relationship between these two variables to be nonexistent or extremely weak (Burke and

others 1989; Richardson and others 1986; Tiedeman

and others 1987).

On extended field trips in 2000 and 2001, I collected

data concerning the relationship of big sagebrush

canopy cover and perennial grass and bare soil cover

in the States of Idaho, Oregon, Washington, and Wyoming (Welch and Criddle 2003). This data set is shown

in table 4.14. I use the 300-foot line intercept method

for determining percent of cover for big sagebrush,

perennial grass, and bare soil. The relationship between big sagebrush cover and bare soil was significant but weakly related in the negative direction, r =

–0.5045; r2 = 0.2546. The negative relationship means

Figure 4.2—A site where the only grass present is

under the protective canopy of mature big sagebrush

(Artemisia tridentata) plants (photo by Bruce L. Welch).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 125

that as big sagebrush cover increases, bare soil would

tend to decrease. Other factors, such as precipitation,

grazing history, soil properties, and community species composition have a greater influence on the amount

of bare soil than does big sagebrush canopy cover

(Daddy and others 1988; Richardson and others 1986).

Branson and Miller (1981), studying the vegetative

changes over 17 years in the Willow Creek basin near

Glasgow, MT, found that in spite of a significant

increase in big sagebrush canopy cover (23 to 30

percent), bare soil decreased significantly (from 40 to

30 percent). They attributed these increases to higher

precipitation and better grazing management.

Mueggler and Stewart (1980) reported that four big

sagebrush habitat types had big sagebrush canopy

cover of 18,, 22, 21, and 24 percent, and bare soil cover

of 11, 4, 3, and 1 percent, respectively. These bare soil

cover values compare to grass habitat types of 24, 9,

14, 7, 18, 9, 12, 12, 5, 5, 1, 1 percent, and so forth

(Mueggler and Stewart 1980). Also, Mueggler and

Harris (1969) found that bare soil in grasslands of

central Idaho varied from 1 to 52 percent with grass

communities dominated by bluebunch wheatgrass

(Agropyron spicatum) having greater percentages (22

percent) of bare soils than communities dominated by

Idaho fescue (Festuca idahoensis) (6 percent) (see

Fosberg and Hironaka 1964; Mueggler and Stewart

1980; Tueller and Eckert 1987 for more data). In

addition, Lusby (1970, p. 258), studying grazed and

ungrazed watersheds, found “marked increase in bare

ground soil and rock on all grazed watersheds, accompanied by a decrease in shrub overstory.” Factors

other than big sagebrush canopy cover are involved in

determining the amount of bare soil in a given area

such as: precipitation, associated or understory species, grazing history, and soil properties (Welch and

Criddle 2003).

I have, on a number of occasions, found sites in Utah,

Idaho, Wyoming, Oregon, Nevada, Colorado, and

Washington where big sagebrush cover has exceeded

Table 4.13—Relation of percent of big sagebrush cover to percentage of bare

ground on 26 Utah big game range trends study sites (data and

pages are from Davis and others 1999).

Percent big

Pages Subspeciesa sagebrush cover Percent of bare ground

7–8 M 16 8

50–51 M 19 12

62–63 W 18 22

71–72 M 4 10

79–80 W 11 7

87–88 W 17 14

96–97 W 14 18

113–114 W 15 12

119-120 M 15 21

128–129 M 24 6

137–138 W 3 29

143–144 W 16 13

152–153 W 9 18

167–168 W 9 8

177–178 W 7 44

187–188 W 12 33

193–194 W 13 21

249–250 M 15 7

263–264 M 9 19

274–275 W 12 18

294–295 M 14 4

313–314 W 14 20

335–336 M 20 29

371–372 W 9 13

379–380 W 17 4

386–387 W 18 20

a M = mountain big sagebrush (Artemisia tridentata ssp. vaseyana); W =

Wyoming big sagebrush (A. t. ssp. wyomingensis).
126 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 4.14—Relation of big sagebrush cover to percent cover of perennial grass and

bare ground based on Welch’s Y2K and Y2K+1 big sagebrush odyssey

through the States of Idaho, Oregon, Utah, Washington, and Wyoming.Data

on file at the Shrub Sciences Laboratory, 735 N 500 E, Provo, UT.Data

were based on 300-foot line transects.Data for the first 12 transects were

collected on ungrazed kipukas in southern Idaho.The three transects per

kipuka were continuous.

Location and Big sagebrush Perennial grass

transect cover cover Bare ground

N43° 31.346'

W112° 28.475' —1 14 56 11

Same —2 16 31 17

Same —3 23 43 12

N43° 19.306'

W113° 38.257' —4 34 58 11

Same —5 30 58 14

Same —6 26 43 21

N42° 52.776'

W113° 08.665' —7 28 41 5

Same —8 14 29 3

Same —9 23 31 4

N42° 52.478'

W113° 07.547'—10 20 45 2

Same —11 24 42 1

Same —12 31 45 2

N43° 26.159'

W112° 46.013'—13 0 43 41

Same —14 20 38 21

N43° 28.815'

W112° 5.296' —15 0 44 44

N42° 36.726'

W113° 14.964'—16 8 10 1

N42° 31.036'

W113° 19.869'—17 5 51 6

N42° 18.861'

W115° 49.612'—18 21 16 38

N42° 2.963'

W115° 51.353'—19 26 33 11

N43° 19.778'

W116° 57.576'—20 19 47 1

N43° 19.716'

W116° 57.414'—21 3 20 21

N42° 54.357’N

W117° 16.888'—22 14 31 37

N42° 54.424'

W117° 17.027'—23 13 54 19

?N

?W —24 31 12 41

N42° 52.202'

W117° 57.389'—25 28 5 2

N43° 11.557'

W118° 21.096’WW—26 41 38 5

N41° 46.191'

W111° 09.274'—27 41 71 4

N41° 53.901'

W109° 21.165—28 22 42 15

N43° 12.303'a

W107° 55.298'—29 24 31 20

N43°12.303'a

W107° 55.298'—30 5 46 24

N44° 07.187'

W107° 15.592'—31 38 67 3

N44° 08.807'

W107° 11.830'—32 50 59 .4

N42° 25.887'b

W111° 08.002—33 29 72 3

a Both line transects share the same starting point.Transect 29 was from south to north,

whereas, transect 30 was from north to south. b Based on a 1500-foot transect moving to the southeast; forb cover was also determined at 28

percent.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 127

Figure 4.4—See figure 4.3 caption (photo by

Bruce L. Welch).

Figure 4.3—General view of an area having an

abundance of grasses and forbs in spite of a 32

percent canopy cover of big sagebrush. Bare

ground was 5 percent. The arrow points to an

orange tagged mature big sagebrush plant that

was cut down to provide a close-up view of the

area that is presented in figure 4.4 (photo by

Bruce L. Welch).

the recommended cover of 15 percent (12 to 20 percent;

Baxter 1996; Winward 1991) and noted lush growth of

grasses and forbs. Figures 4.3 and 4.4 illustrate such

a site. On this site in Utah, the mountain big sagebrush cover was 32 percent, and the mountain big

sagebrush plants were about 42 years of age with just

5 percent bare ground and a well-developed understory of grasses and forbs.

Big Sagebrush Cover Versus Perennial

Grass Cover

Daubenmire (1970, p.13) describes the lack of a

relationship between big sagebrush coverage and the

coverage of perennial grasses:

One might question whether the stands with more

Artemisia also have less of the perennial forage grasses

and more of the annuals favored by grazing...But when

the stands are listed in order of the coverage of Artemisia..., there is neither positive correlation with the

grazing increasers, nor negative correlation with the

preferred forage species.

R2 and r values for his table 3 were 0.0004 and 0.0208,

respectively; or in other words, no relationship existed

between big sagebrush canopy cover and perennial

native grass cover (also see Baker and Kennedy 1985;

Doescher and others 1986; Richardson and others

1986).

Calculated r and R2 values between big sagebrush

canopy cover and perennial grass cover for my data set

in table 4.14 were not significant at +0.2130 and

0.0454, respectively. Mean big sagebrush canopy cover

for this data set was 21.8 percent (range 0 to 50

percent) and for perennial grass cover 41.0 percent

(range 5 to 72 percent). Highest perennial grass cover

values were found in big sagebrush stands having

above average canopy cover of 29 percent (transect 33-

grass cover = 72 percent), 41 percent (transect 27-

grass cover = 71 percent), and 38 percent (transect

31-grass cover = 67 percent). This data set does not

support the contention that big sagebrush canopy

cover above 15 percent decreases perennial grass

cover (Welch and Criddle 2003).

Tart’s (1996) report contained 29 data sets, his plant

community composition, comparing mountain big sagebrush canopy cover with perennial grass and forb

cover. These comparisons are listed in table 4.15 along

with means, standard deviations, range, correlation

coefficients, and coefficients of determination. Lowess

statistical analysis was also performed on this data set

(Chamber 1983). Results from both statistical procedures were in agreement. A quick glance through table

4.15 clearly shows no relationship between mountain

big sagebrush canopy cover and perennial grass cover

and between mountain big sagebrush canopy cover

and perennial forb cover. Mean canopy of mountain

big sagebrush was 28.03 percent, which is well above
128 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

the 12 to 15 percent limits set by Baxter (1996) or 12

to 20 percent limits set by Winward (1991). Mean

cover of perennial grass was at 51.59 percent, and

cover of perennial forbs was at 34.10 percent. These

values demonstrate that on 26 of these sites there was

an abundance of big sagebrush (20 percent or more),

perennial grass (50 percent or more), and perennial

forbs (15 percent or more).

Tart’s (1996) data showed that plant communities

of mountain big sagebrush with the highest canopy

cover at 46 percent had grass and forb cover above the

study averages; conversely, plant communities of

mountain big sagebrush with the lowest canopy cover

at 17 percent had below average grass and forb cover.

This report does not support the contention that

mountain big sagebrush canopy cover above 20 percent

Table 4.15—Relationship of mountain big sagebrush (Artemisia tridentata ssp. vaseyana)

canopy cover to perennial grass cover and perennial forb cover and to number of

grass and forb species and to total number of plant species. Data and page

numbers refer to Tart (1996). His plant communities tables.

Page Mountain Grass Forbs Total number

number sagebrush cover (%) cover (%)a cover (%)b of plant speciesc

26 21 52 (11)a 17 (18)b 44c

26 43 (10) 13 (18) 42

17 38 (10) 22 (18) 44

31 21 48 (11) 27 (25) 45

24 47 (11) 31 (25) 46

23 36 (11) 35 (26) 47

37 30 55 (13) 20 (16) 35

31 51 (9) 24 (18) 33

22 22 (10) 19 (19) 36

42 31 61 (10) 25 (24) 46

46 58 (10) 35 (25) 46

34 40 (10) 33 (25) 47

47 22 79 (13) 27 (19) 39

34 69 (16) 46 (19) 43

17 41 (16) 47 (19) 43

52 27 67 (11) 22 (16) 33

24 54 (11) 22 (13) 36

57 29 63 (14) 26 (19) 44

30 49 (12) 34 (21) 43

30 72 (14) 40 (21) 47

62 28 53 (9) 48 (19) 33

31 57 (11) 79 (23) 39

30 52 (11) 60 (23) 41

67 37 55 (8) 11 (17) 29

34 53 (14) 29 (19) 40

30 40 (12) 31 (21) 39

72 30 70 (9) 58 (21) 38

26 40 (8) 67 (21) 36

26 30 (8) 41 (16) 29

__ __ __

Mean 27.97 51.59 34.10

S. D. ±6.15 ±13.02 ±16.32

Range 17-46 22-79 11-79

a

 Number of grass species.

b

 Number of forb species.

c

 Number of total plants species.

r = 0.3289; R2 = 0.1082 (mountain big sagebrush canopy cover versus perennial grass cover) not significant.

r = 0.1092; R2 = 0.0119 (mountain big sagebrush canopy cover versus perennial forbs cover) not significant.

r = –0.0966; R2= 0.0093 (mountain big sagebrush canopy cover versus number of grass species) not significant.

r = 0.1933; R2 = 0.0374 (mountain big sagebrush canopy cover versus number of forb species) not significant.

r = –0.0738; R2 = 0.0054 (mountain big sagebrush canopy cover versus total number of plant species) not

significant.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 129

suppresses grass and forbs species cover or species

numbers.

In addition, statistical analyses (both correlation

and lowess analyses) conducted on Tart’s (1996) seral

stages data, found that total shrub canopy cover

(dominated by big sagebrush) was positive but weakly

related to graminoids cover; meaning as total shrub

canopy cover increased, graminoids cover tended to

increase too (table 4.16). Total shrub canopy cover

(dominated by big sagebrush) was not significantly

related to forb cover (table 4.16). A significant negative

relationship was detected between total shrub canopy

cover (dominated by big sagebrush) and bare soil;

meaning as total shrub canopy cover increased, the

amount of bare soil tended to decrease (table 4.16).

The two data sets from Tart (1996; tables 4.15, 4.16)

do not support his often repeated statement (Tart

1996, p. 27, 32, 38, 43, 48, 58, 63, 69, 73): “If sagebrush

canopy cover exceeds 20 percent for a long period of

time, the density, cover, and biomass of herbaceous

Table 4.16—Relationship of total shrub canopy cover to cover of graminoidsa, forbsb,

and bare soilc

. Big sagebrush (Artemisia tridentata) was the dominant

shrub for all plant associations described. Data obtained from the reort

of Tart (1996), his seral stages.

 Page Total Total graminoids Total forbs Bare

number shrub (%) cover (%) cover (%) soil

25 29 37 12 13

33 28 8 18

20 26 16 16

32 28 41 16 8

23 33 14 16

21 14 17 22

36 38 45 17 9

35 35 14 14

17 20 15 25

43 29 53 16 7

30 44 25 7

26 25 18 21

46 31 48 23 7

40 43 32 8

25 22 29 17

51 27 57 17 10

25 53 18 3

58 29 53 18 6

30 40 24 5

26 37 22 13

63 28 48 33 6

32 44 41 13

29 37 39 6

68 45 50 10 1

26 43 18 11

30 29 23 9

73 25 57 30 7

26 39 35 9

26 32 25 8

__ __ __ __

Mean 28.6 39.1 21.6 10.9

S.D. ±5.81 ±11.36 ±8.52 ±5.83

Range 17-45 14-57 8-41 1-25

a

r = +0.4404; R2 = 0.1940 (total shrub canopy cover-dominated by big sagebrush versus

graminoids cover) weakly related in a positive direction; meaning as total shrub canopy cover

increased, graminoids cover also increased. b

r = –0.0257; R2 = 0.0007 (total shrub canopy cover-dominated by big sagebrush versus forb

cover) ns. c

r = –0.5445; R2 = 0.2964 (total shrub canopy cover-dominated by big sagebrush versus bare

soil) significantly related in a negative direction; meaning as total shrub canopy cover increased,

bare soil decreased.
130 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

species will be reduced through shading and competition for moisture.” One possible explanation could be

the positive effect of canopy shading on soil moisture.

Pearson (1965), studying vegetative production in

grazed and ungrazed plant communities, found that big

sagebrush canopy cover in the ungrazed area was 34

percent and perennial grasses 41 percent, compared to

11 percent big sagebrush cover in the grazed area with

22 percent perennial grass cover. Similarly, Anderson

and Holte (1981) reported that, for an area in southeastern Idaho protected from grazing for 25 years, Wyoming

big sagebrush canopy cover increased from 15 to 22

percent with an increase in grass cover from 0.28 to 5.6

percent. This work has been extended to more than 45

years by Anderson and Inouye (2001) who found that

the maximum canopy cover of Wyoming big sagebrush

(20 percent) and maximum cover of perennial grasses

(6.2 percent) occurred in 1975 (their figure 4), and both

have declined from these maxima. McLean and Tisdale

(1972) found that from 1959 to 1968 in their West Mara

exclosure that cover of perennial grasses increased in

spite of a constant big sagebrush canopy cover at 31 to

34 percent. This was also true for the grazed area next

to the exclosure. Another interesting data set comes

from the study of Doescher and others (1984) where

they selected two types of sites—those having high big

sagebrush canopy cover and low grass cover, and those

having low big sagebrush canopy cover and high grass

cover. The calculated r and R2 values were not significant, but what was most interesting is that for both

types of sites, the study plot with the greatest big

sagebrush canopy cover for either site type also contained the greatest grass cover for that site type (26.0

versus 8.2 percent, and 20 versus 27.5 percent). Smith

(1969) reported a big sagebrush canopy cover at his

Soldier Creek site of 24 percent, but it produced 750

pounds per acre of grass versus his Buck Creek site of

14 percent big sagebrush canopy cover that produced

only 230 pounds per acre of grass.West and York (2002;

their fig. 3 and 4) found that burned and ungrazed

exclosures contained higher cover of perennial grasses

than burned grazed macroplots 17 out of 19 years.

Unburned and grazed (their fig. 5) macroplots had

cover of perennial grasses greater than burned grazed

macroplots 10 out of 19 years. Yorks and others

(1992, p. 569) reported increasing big sagebrush

canopy cover and increasing grass cover together

over 56 years and noted, “Some of the observed shifts

of dominance/diversity are contrary to widely accepted

expectations in the literature.”

Wambolt and others (2001) studying the recovery

rate of big sagebrush after burning give 26 data points

concerning big sagebrush cover and perennial grass

cover in their tables 2 and 5. Big sagebrush cover

ranged from 0.00 to 28.3 percent and grass cover

ranged from 16.3 to 61.7 percent. Correlation coefficient (r) and coefficient of determination (R2

) were not

significant. Determining r and R2 for big sagebrush

stands having higher than 15 percent cover with grass

cover yielded nonsignificant values. Wambolt and

others (2001, p. 243) concluded: “Managers considering prescribed burning of big sagebrush communities

should be aware that herbaceous plant responses may

be minimal while shrub values will likely be lost for

many years. The loss of the dominant shrubs in any

ecosystem will affect many other organisms and severely impact species that have an obligate habit with

the shrubs.” Branson and Miller (1981) studying the

vegetative changes over 17 years in the Willow Creek

basin near Glasgow, MT, found that in spite of a

significant increase in big sagebrush canopy cover

(23 to 30 percent), grass cover also increased significantly (3 to 41 percent). Peterson (1995, p. 12) has

reported similar observations in Montana and concluded, “In fact, well-developed grass and forb understories are commonly associated with big sagebrush

stands on ranges that have proper grazing management practices.”

Nitrogen Metabolism_____________

For higher plants, such as big sagebrush, nitrogen is

the fourth most abundant nutrient element in dry

matter. For big sagebrush, the leaves contain 58 percent

of the nitrogen in aboveground parts with 1-year-old

shoots containing 10 percent and old stems 32 percent,

so the leaves are the main source of nitrogen (Bilbrough

and Richards 1993). Nitrogen is an important structural component of many primary and secondary compounds such as proteins, nucleic acids, hormones,

chlorophyll, alkaloids, polyamines, and so forth. Nitrogen appears in several inorganic forms in nature

including gaseous (N2), nitrite (NO2

–

), nitrate (NO3

–

),

ammonia (NH3), and nitrogen oxides (NO and N2O).

The most abundant form is gaseous nitrogen in the

atmosphere, but higher plants such as big sagebrush

are unable to convert gaseous nitrogen into a physiologically useable form. Big sagebrush must depend

on prokaryotic organisms, living in the soil, to convert

atmospheric nitrogen into useful forms of nitrogen

(nitrates and ammonia). These are then absorbed

from the soil, but the supply is limited. Plants not only

compete among themselves for limited supplies of

nitrates and ammonia but are also pitted against soil

microorganisms. Thus, in arid and semiarid settings,

soil nitrogen availability is second only to soil moisture

availability as a limiting factor for plant growth (James

and Jurinak 1978; O’Brien 1978; Wallace and others

1978; West and Klemmedson 1978).

For big sagebrush, as well as other dominant arid

and semiarid shrub species, nitrogen accumulates

toward the soil surface and under the shrub canopy,
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 131

resulting in “islands of fertility” across the landscape

(Chambers 2001; Charley and West 1975, 1977;

Doescher and others 1984; Fairchild and Brotherson

1980; Halvorson and others 1994; Wikeem and Pitt

1982). Charley and West (1975), reporting on a percent of dry-weight basis, noted that total nitrogen

content of surface soil under big sagebrush plants was

0.233 percent compared to interspace content of

0.151 percent. It was suggested that concentrating of

nitrogen under big sagebrush canopy was closely related to the decline of nitrogen levels in the interspaces.

Charley and West (1975) suggested that three factors may be operating in concert to account for the

accumulation: first, enhanced fixation by free-living

microorganisms in or under litter; second, animal activity; and third, canopy capture of wind-transported

solids. Further, they reported that nitrogen levels

were significantly higher under big sagebrush canopy

than under grass (Agropyron desertorum) and other

shrub communities.

Charley and West (1977, p. 357), studying nitrogen

mineralization activity of surface soil under big sagebrush canopies and interspaces, found “mineralization of N proceeded at a greater rate in soils beneath

shrub canopies than in soils from interspace areas

between shrubs.” They concluded that this mineralization process increased nitrogen availability and in

turn “water-use efficiency of the vegetation.” In addition, Charley and West (1977) reported total nitrogen

under big sagebrush canopy cover exceeded that in

interspace by a factor of 1.85 (296 versus 160 ug g–1)

and that this value was among the highest for the

eight communities studied. Fairchild and Brotherson

(1980) found that nitrogen levels under big sagebrush

canopy were greater by a factor of 1.67 than levels

between big sagebrush plants (559.6 versus 335.0

parts per million). Not only were nitrogen levels higher

under big sagebrush canopies but the soils were significantly deeper under canopies than in areas between big sagebrush plants (45.2 versus 37.8 cm).

Studies conducted in British Columbia by Wikeem

and Pitt (1982), in Oregon by Doescher and others

(1984), and in Wyoming by Burke (1989) further support the findings of the previous studies cited in this

section.

A few studies have been conducted to measure the

response of big sagebrush to supplemental nitrogen

fertilization. Results varied among studies. Greenhouse studies conducted by Wallace and others (1978)

showed that big sagebrush plants respond to nitrogen

fertilizer by increases in both dry matter production

and nitrogen foliage content. Toft and others (1989),

using field plants, found that additional nitrogen increased the photosynthetic rate of Wyoming big sagebrush plants. Miller and others (1991b), studying the

effects of nitrogen amendments on a Wyoming big

sagebrush site, found that additional nitrogen

increased biomass production of Wyoming big sagebrush. Elderkin and others (1986), studying effects of

nitrogen/phosphorus fertilization and irrigation on

big sagebrush, found that irrigated-fertilized plants

were significantly more productive, preferred by wintering mule deer, and contained higher levels of crude

protein, phosphorus, and monoterpenoids than irrigated and control plants. Elderkin and others (1986, p.

144) stated: “Overall, our investigation indicated that

big sagebrush was a good winter deer browse and that

production, utilization, and nutritive value could be

enhanced by irrigation and the addition of a nitrogenphosphorus fertilizer.” Bayoumi and Smith (1976)

found that spring applications of nitrogen significantly increased the percent of crude protein in forage

of big sagebrush and that nitrogen-fertilized plants

were used more heavily by elk than unfertilized plants.

Doescher and others (1990) observed that both nitrate

and ammonium treatments significantly increased

leaf nitrogen content, mean maximum length of ephemeral leaves, number of ephemeral leaves per terminal

shoot, and current year’s vegetative stem length of big

sagebrush plants over control plants. Doescher and

others (1990, p. 9) concluded: “This study suggests

A. tridentata ssp. wyomingensis would opportunistically take advantage of increased availability of

soil nitrogen. The ability of this species to respond

positively to increased soil nitrogen may enhance its

competitiveness over associated perennial species.”

However, Booth and others (1990) discovered that, in

a nonlimiting environment, both top growth and growth

rate of Wyoming big sagebrush are under genetic

control that appears to be size limiting. In contrast to

previous reports, Carpenter and West (1987) noted no

response of mountain big sagebrush to small annual

additions of nitrogen fertilizer. Sneva (1978) noted

that nitrogen and sulfur fertilizers increase big sagebrush establishment in wet years but not for dry years.

BassiriRad and Caldwell (1992) conducted a study

to determine how drought and recovery from drought

affects nitrate uptake in big sagebrush. Drought conditions were created in greenhouse-reared big sagebrush seedlings by reducing water allotments to onethird of the well-watered seedlings (controls). This

water deprivation lasted for 24 days after which the

water-stressed seedlings received the full water allotment of the well-water seedlings. Uptake of nitrate in

water-deprived plants was reduced by 40 percent, and

this reduction lasted 4 days after receiving full water

allotment, but after 4 days nitrate uptake of previously stressed plants was equal to the well-watered

seedlings. They found that water deprivation changed

the distribution patterns of newly acquired nitrates.

Water-stressed seedlings allocated a greater proportion of newly acquired nitrates to the roots than the
132 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

well-watered plants (also see Dina and others 1973).

This continued 4 days after receiving full water allotment. After 14 days, the allocated pattern of nitrate

was the same for the two groups of seedlings. Based on

root relative growth rate of water-stressed seedlings

(rate was one-fourth of control during drought and

three times greater than control, 4 days after the

drought), lack of osmotic adjustment, a loss of turgor,

and equal rate of nitrate uptake after drought,

BassiriRad and Caldwell (1992, p. 493) concluded:

“The pattern of NO3

- uptake upon rewatering was

apparently more closely associated with root uptake

capacity” than root growth. Dina and Klikoff (1973)

found that water-stressed big sagebrush moved nitrogen out of leaves and into stems and roots; however,

total level of nitrogen in the entire plant remained the

same. These shifts are evidence of adaptation for

conservation of nitrogen during periods of water

stress, and the nitrogen pool stored in the stems may

be shifted again to the leaves once water stress is

relieved.

Phosphorus Metabolism _________

The primary source of phosphorus is not the atmosphere, as is the case for nitrogen, but is the Earth’s

crust. Weathering of rocks and decomposition by fungi

and bacteria in the soil of organic phosphorus creates

three forms of polyprotic phosphoric acid (H3PO4)—

monovalent, divalent, and trivalent. The exact form of

phosphoric acid that is most prevalent in a soil is

dependent on soil pH. In soils having a pH of 6.8 and

lower, the prevailing form of phosphorous is the

monovalent orthophosphate. This anion is readily

absorbed by plants’ roots. The divalent form of phosphorous is most prevalent in soil having a pH between

6.8 to 7.2 and is not as readily absorbed by plant roots.

For soil having a pH above 7.2 or alkaline soils, the

trivalent form of phosphorous is most abundant. Unfortunately, trivalent phosphorous is unavailable to

plants. In neutral pH soils, phosphorus can form

complexes with aluminum and iron that render the

phosphorous insoluble, while in basic soils it forms

insoluble complexes with calcium and magnesium.

Insoluble phosphorous is released slowly into the soil

solution. Phosphorous is almost immobile in soils and

plant roots, and with their associated mycorrhizae,

must be within a few millimeters of phosphorous in

order for uptake to occur. Phosphorous is limited in

highly calcarious soils. However, mycorrhizal associations enhance the uptake of phosphorous, thus helping to supply this important nutrient in the quantity

need (Hopkins 1999).

Phosphorous, as phosphate esters, plays an important role in energy transport at the photosynthesis

and intermediary metabolism levels. In addition,

microorganisms that are involved in nitrogen fixation

require some phosphorous, and limiting supplies may

interfere with nitrogen fixation. Phosphate esters are

found in the structure of a number of molecules—

adenosine triphosphate (ATP), adenosine diphosphate

(ADP), a host of phosphorylated sugars and organic

acid, nucleotide, phospholipids, several coenzymes,

and many more (Hopkins 1999).

Mack (1977), studying the production of litter and

mineral return to soil of big sagebrush, reported that

annual return of available phosphorous was 127.2 kg/

ha—this in spite of mass withdrawal of phosphorous

from senescent leaves into the plant prior to leaf fall.

Mack (1977, p. 196) further observed:

Certainly the total amount of ash elements returned

via Artemisia litter is small compared to the amounts in

the soil nutrient sink. However, Artemisia may play an

important role in the community by increasing the

effective zone in the solum from which these nutrients

are regularly recycled to the soil surface. This cycle is

important particularly for relatively shallow-rooted

associates. Such benefit should be considered in evaluating the wholesale eradication of the shrub to increase

rangeland.

It appears that phosphorous accumulates under the

canopy of big sagebrush similar to the accumulation of

nitrogen. Fairchild and Brotherson (1980) and Chambers (2001) reported significantly higher concentrations of phosphorous under the canopy of big sagebrush than in adjacent areas. In an Oregon study,

Doescher and others (1984) found higher soil surface

levels of phosphorous under the canopies of big sagebrush than in interspace and grass influenced soils.

Charley and West (1975) reported significantly higher

levels of soil surface organic phosphorous under big

sagebrush canopies than in interspaces, equal levels

of bicarbonate-phosphorous at both locations, and

greater amounts of total phosphorous in the interspaces

than under canopies.

Because of phosphorous immobility in soil and the

presence of two radio-active isotopes, 32P and 33P,

workers have been able to design experiments to

measure the competitiveness for this element of plants

growing together (Black and others 1994; Caldwell

and others 1985, 1991a). Caldwell and others (1985)

describe a method for determining the relative competitiveness of big sagebrush, and a native grass

associate, bluebunch wheatgrass (Agropyron

spicatum), and an exotic grass from Eurasia, crestedwheatgrass (A. desertorum). The first stage of the

experiment was to establish a garden; in this case,

three species were transplanted in an evenly spaced

matrix (0.5 m). Each big sagebrush plant was surrounded by four plugs of grasses, two of each grass

species on opposite sides. The transplants were allowed to grow for at least 6 years to ensure thorough

intermingling of root systems. Next, small holes were

created by the use of steel rods halfway between the
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 133

big sagebrush plants and the grass plants, and then

isotopes 32P and 33P were injected into the 30-cm-deep

holes. Using this dual-isotope technique, Caldwell and

others (1985, p. 229) found that the uptakes of phosphorous between the two species of grasses were very

different: “Of the total phosphorus-32 and -33 absorbed by Artemisia, 86 percent was from the interspace shared with Agropyron spicatum and only 14

percent from that shared with Agropyron desertorum.”

They concluded that the exotic grass species was

better able to compete with big sagebrush for phosphorus than the native grass (Black and others 1994;

Jackson and Caldwell 1989; Jackson and others 1990).

Under shading, the exotic grass species outcompeted

big sagebrush for nitrogen and phosphorus (Cui and

Caldwell 1997). However, the Caldwell group, in another study (Caldwell and others 1987), found that

defoliating neighboring grass plants increased phosphorus uptake by big sagebrush sixfold over the uptake of unperturbed neighbors. Caldwell and others

(1987, p. 616 ) concluded: “The rapid shift in resource

acquisition demonstrated in these experiments not

only indicates immediate resource competition, but

also shows how quickly the balance of competition

might change in the event of herbivory.” Further, they

stated (p. 616): “We do not, however, feel that P is the

only, nor necessarily the pivotal, resource in the competitive balance of these plants.” West and others

(1984) also noted that exotic crested wheatgrass stands

removed more phosphorus from the soil than native

stands of big sagebrush and voiced concerns that such

export could lead to long-term declines in productivity.

Van Auken and others (1992), studying the uptake

of phosphorus by seedlings of big sagebrush, crested

wheatgrass, and bluebunch wheatgrass grown in pots,

with interspecies competition and without, found that

juvenile big sagebrush plant uptake of phosphorous

was four to five times greater than crested wheatgrass

and seven to eight times greater than bluebunch

wheatgrass. These observations again show the competitiveness of crested wheatgrass, an exotic species,

to absorb phosphorus more readily than the native

grass bluebunch wheatgrass.

Billings (1950) described isolated stands of Sierran

conifers, mainly Pinus ponderosa andP. jeffreyi, growing in the midst of big sagebrush vegetation. The open

woodland communities were growing on soils derived

from hydrothermally altered andesite. For the most

part, these two plant communities did not mix, and the

Sierran conifer communities were growing on sites

dryer than normal. When Sierran conifers and big

sagebrush were grown in soil from the Sierran sites,

growth of the conifers was 72 to 90 percent of the

growth of plants grown in unaltered andesite—10

percent for big sagebrush (Delucia and others 1989).

This retarding of growth was attributed to low

phosphorus levels and lower pH values, which were

more severely expressed in big sagebrush than in

Sierran conifers (Delucia and others 1989; Gallardo

and Schlesinger 1996; Schlesinger and others 1989).

Trace Elements _________________

During the mid-1970s to the early 1980s, some

research was conducted on trace element content of

big sagebrush. This was done to determine whether or

not big sagebrush could be used to monitor the level of

fine particles, trace metals, and other contaminants

being released by mining and electrical general operations and other activities of man. Natural variations

due to season and region for trace elements have been

established and baseline levels established. The reader

is referred to the following publications for details:

Connor and others (1976); Gough and Erdman (1980,

1983); Rickard and Garland (1983); Rickard and Van

Scoyoc (1984); Severson and Gough (1976).

Photosynthesis and Carbohydrate

Metabolism ____________________

Photosynthesis

In spite of the discovery of bacterial chemosynthesis-based ecosystems in dark, deep oceanic trenches,

photosynthesis by green plants and other organisms is

still the foundation of life on this planet. Photosynthetic organisms are able to convert light energy into

chemical energy and reduce carbon dioxide into one of

two organic acids, either a three-carbon acid (3-phosphoglycerate) or four-carbon acid (oxaloacetate). The

first stable product of big sagebrush photosynthetic

process is 3-phosphoglycerate; thus big sagebrush is

classified as a C3 plant as opposed to a C4 plant or CAM

plant.

In C3 plants, photosynthetic reactions are divided

into two major groups: energy-transduction reactions

and carbon-fixation reactions. During the energy transduction reactions, light energy is captured by photosynthetic pigments chlorophylls, carotenoid, and

phycobilins, and used to split water molecules in the

production of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and nicotinamide adenine

dinucleotide, reduced (NADH) from nicotinamide adenine dinucleotide, oxidized (NAD+

). These two molecules (ATP and NADH) then furnish the fuel needed

to drive the carbon-fixation reactions, commonly called

the Calvin cycle, into the basic building unit of all

organic compounds (3-phospoglycerate). The carbon

dioxide used in the Calvin cycle diffuses from the

atmosphere into the leaves through stomata.
134 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

When C3 plants are exposed to hot, dry conditions,

stomata close to conserve water and thus cut off the

supple of carbon dioxide to the leaves. Oxygen, a

byproduct of water splitting, accumulates, and a series of reactions takes place called photorespiration.

The results of photorespiration are the consumption of

oxygen and the production of carbon dioxide, an

“undoing of photosynthesis” so to speak, a wasteful

process that yields neither ATP nor NADH. Photorespiration should not be confused with mitochondrion respiration of the Krebs cycle, sometimes called

“dark respiration.”

The photosynthetic rate of big sagebrush varies

seasonally and daily within season (Caldwell 1979;

DePuit 1979; DePuit and Caldwell 1973, 1975a; Mooney

and others 1966; Moore 1977; Pearson 1975). Seasonally, DePuit and Caldwell (1973) reported highest

photosynthetic output in late May and early June

when temperatures and soil moisture were most favorable, and photosynthesis declined to minimum

output in August when soil moisture was also at a

minimum. Pearson (1975) observed higher photosynthetic rates in July than in June. He attributed this to

the occurrence of heavy rains in late June and early

July, which replenished soil moisture. During mid

summer drought, Mooney and others (1966) noted a

marked reduction in the growth of big sagebrush but

a return to a higher growth level after rain had

recharged the soil in early August. DePuit and Caldwell

(1975a), studying the photosynthetic rates of irrigated

and nonirrigated big sagebrush at varying temperatures (5 to 40 °C), found that irrigation stimulated

photosynthesis at all temperatures (also see Toft and

others 1989). Big sagebrush is an evergreen, and there

is evidence that some photosynthesis takes place year

around (Pearson 1975; Smith and others 2002).

Daily patterns of photosynthetic rate vary with

season. During the spring and early summer when

temperatures are not excessive and soil moisture

readily available, photosynthetic rates are lowest at

sunrise and sunset and peak at about midday (Caldwell

1979; DePuit and Caldwell 1973). As the growing

season advances and temperatures become warmer

and soil moisture is less available, peak photosynthetic rates occur at midmorning, and by midday

photorespiration has overwhelmed photosynthesis,

and net carbon fixation becomes negative and remains

so for rest of the day. Photorespiration increase is due

to stomata closure and buildup of oxygen levels inside

leaves of the big sagebrush plants. However, Pearson

(1975, p.15) noted in his study for

midsummer:

All six plants tended to follow the same photosynthesis

pattern with the highest rates occurring in midmorning

and late afternoon. Rates of photosynthesis were low

before sun up and for an hour or two after sun up before

reaching the morning peak, and then dropped again

following the peak. During the hottest part of the day,

when presumably the roots could not absorb water fast

enough to make up transpiration losses unless the

stomates were closed, the photosynthetic rates generally became negative, indicating that respiration was

continuing but that gross photosynthesis had essentially ceased. In the late afternoon, photosynthesis

became positive.

Pearson (1975) goes on to suggest that stomata close

tightly enough to allow water to accumulate in the

photosynthetic tissue to the point that the stomata

again open, allowing carbon dioxide to diffuse in, thus

allowing the resumption of photosynthesis and a net

gain of carbon.

The optimum temperature for photosynthesis in big

sagebrush appears to be about 20 0C (DePuit and

Caldwell 1973, 1975a,b; greenhouse studies of Mooney

and others 1966 and West and Mooney 1972). However, optimum temperature for photosynthesis in big

sagebrush varies according to the environment it has

been exposed to (Mooney and West 1964). For instance, Mooney and others (1966) were able to shift the

optimum temperature for a high-elevation (10,150

feet) population of big sagebrush from 10 to 20 °C.

They noted that the greenhouse big sagebrush plants

grown at Los Angeles had higher photosynthetic rates

at all test temperatures than field plants tested at

different times through out the growing season. West

and Mooney (1972) collected uniform-sized seedlings

of big sagebrush from a lower (2,400 m) elevation site

and a higher (3,090 m) elevation site. The seedlings

were transplanted into pots, reared in a greenhouse

for 6 months, and then maintained in field

autoirrigators at the two elevations for 2 months; after

which the photosynthetic rates of the seedlings were

determined for various temperatures. At the higher

site, seedlings had an optimum photosynthetic temperature of 15 °C compared to the seedlings collected

at the lower site of 20 °C. At the lower site, the two sets

of seedlings showed a shift in optimum photosynthetic

temperature of 5 °C, higher elevation seedlings 20 °C,

and the lower elevation seedlings 25 °C. Regardless of

site, seedlings from the higher site, or cooler site, did

better at the cooler temperature, and the seedlings

from the lower site, or warmer site, did better at the

warmer temperatures. These sets of data suggest a

genetic as well as an acclimation component in determining optimum photosynthetic temperature. Caldwell

(1979, p. 79), after reviewing the West and Mooney

(1972) study, stated, “Therefore, although Artemisia

tridentata exhibited a notable acclimation potential,

its successful widespread distribution must be attributed to genetic differentiation within the species.”

Growth in big sagebrush is a two-phase process: first

vegetative growth and second reproductive growth

(Miller and others 1983). Vegetative growth occurs during spring and early summer when temperatures and

water supplies are usually optimum. Reproductive
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 135

growth starts in early summer and reaches maximum

growth during late summer with florets fully developed by late summer to early fall (DePuit and Caldwell

1973; Evans and others 1991). Flowering occurs during early to mid fall with fruit development commencing almost simultaneously with flowering (DePuit and

Caldwell 1973). Thus, reproductive growth occurs

when water supplies and temperatures are not particularly favorable; in fact, during this period, big

sagebrush plants have started shedding ephemeral

leaves from vegetative shoots, and neighboring plant

species are largely dormant (Miller and others 1983).

Evans and Black (1993) found, through the use of a

carbon isotope, that vegetative fixed carbon does not

transfer to reproductive structures. Further, they found

that inflorescences of big sagebrush do generate positive net photosynthesis at a time when the whole plant

is in a water conservation mode; that is, leaf abscission

is occurring and stomata are exerting control over

water loss. Evans and Black (1993, p. 1524) noted:

“Vegetative and reproductive modules both responded

to the limited availability of water and increased

evaporative demand by abscising leaves and decreasing stomatal conductance. Reproductive modules, however, consistently had higher transpiration rates.”

They reported that supplemental watering stimulated inflorescences growth but not vegetative growth

(also see Evans and others 1991). Evans and others

(1991, p. 676) stated:

Expanding inflorescences during summer may enhance

competitive ability because biomass can be allocated

solely toward vegetative growth during spring, increasing the capacity of Artemisia tridentata to acquire

resources when they are most abundant. Conversely,

inflorescences that are photosynthetically self-sufficient can better respond to favorable soil moisture or

intermittent precipitation during summer, because

photosynthesis can be increased without investing resources into further vegetative growth.

A study conducted by DePuit and Caldwell (1975b)

determined that net photosynthesis of green stems of

big sagebrush was low. They concluded that big sagebrush, which maintains a large amount of leaves

during dry periods, would be less dependent on carbon

fixation by stem tissues during such periods, whereas

plants species that shed many, if not all, of their leaves

during drought may depend more on stem photosynthesis for supplying the energy needed for tissue

maintenance.

Frank and others (1986) studied the relationship of

big sagebrush subspecies (basin, mountain, Wyoming)

growth rates with rates of photosynthesis, transpiration, and 13C. They found that basin big sagebrush

growth rate was significantly higher than mountain

and Wyoming big sagebrush. Frank and others (1986,

p. 335) noted: “Subspecies of big sagebrush that exhibit

rapid growth also show high rates of photosynthesis

(reflected in less isotopic fractionation) and high rates

of transpiration.”

Ducharme and Ehleringer (1996) measured the photosynthetic rate, 13C, and heterotrophy of Castilleja

linariifolia, a facultative root hemiparasite of big

sagebrush. They calculated that 40 percent of the C.

linariifolia leaf carbon was derived from its big sagebrush host. Also, Hansen (1979) described the movement of reducing sugars from parasitized big sagebrush plants to a parasite desert paintbrush (Castilleja

chromosa).

Carbohydrate Metabolism

Closely related to photosynthesis is carbohydrate

metabolism. Unlike other plant species, seasonal trends

(increases and decreases in concentration of

nonstructural carbohydrates such as starch, sugars,

and so forth) were lacking for crown and root tissues of

big sagebrush (Coyne and Cook 1970; Garrison 1972).

But twigs of big sagebrush showed a pronounced

seasonal trend starting off high in the spring, reaching

lowest levels in the summer, and building back in the

fall (Coyne and Cook 1970). Twigs contained significantly higher concentrations of nonstructural carbohydrates than entire crowns or root systems. What is

unusual about big sagebrush is the high concentration

of nonstructural carbohydrates in the spring. Most

plant species are using carbohydrate reserves at this

time of year to support new growth, thus carbohydrates are at their seasonally lowest level. It appears

that the overwintering leaves of big sagebrush can

more than support the needs of nonstructural carbohydrates for new spring growth. Bilbrough and

Richards (1993) found that over 45 percent of the

nonstructural carbohydrates of twigs were stored in

the leaves, 42 percent in older shoots, and 13 percent

in 1-year-old long shoots. Coyne and Cook (1970, p.

439) pointed out: “In big sagebrush, twigs are apparently an important site of reserve storage. This would

appear to be an efficient adaptation provided the twigs

are not removed by grazing. If grazed, much of the

stored carbohydrates could be directly removed by the

animals.” In fact, Trlica and Cook (1971) found that

removing 90 percent of the twig’s tissues in either

spring, summer, or fall resulted in reduced fall concentrations of nonstructural carbohydrates in crowns and

roots tissues as compared to nondefoliated plants.

Wandera and others (1992) reported killing of mountain big sagebrush plants when removing 90 percent of

the previous year’s growth either in the winter or

spring. Heavy grazing during the spring is most detrimental to big sagebrush (Bilbrough and Richards

1993; Cook and Child 1971; Cook and Stoddart 1963;

Pearson 1964). Also, heavy winter and spring grazing

reduces the number of fall flowering stocks, but this
136 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

may be due more to the removal of flowering buds

located at the distal end of long shoots than loss of

carbohydrates (Bilbrough and Richards 1993;

Rodriguez and Welch 1989). Cook and Stoddart (1960,

p. 15) observed: “It was found that clipping all of the

current year’s growth from one side of the plant during

late winter or early spring caused death of that onehalf of the plant after three years of treatment; whereas

clipping one-half of all the current year’s growth over

the entire plant reduced vigor of the entire plant

substantially, but only small isolated twigs or branches

were killed.” Or in other words, carbohydrates and

perhaps other compounds are not translocated from

one side of big sagebrush plants to the other side.

Dina and Klikoff (1973), studying the effects of

moisture stress on carbohydrate concentrations in big

sagebrush, found that starch levels were not affected,

but sugar concentrations increased significantly in

leaves, stems, and roots of water-stressed plants. This

increase in sugar levels may provide some protection

to RNA-DNA complex, enzymes, and other cellular

organelles during periods of high water stress—an

adaptive mechanism.

Water Relationships _____________

Knowledge of the morphology of big sagebrush root

system and leaf production and leaf shed is essential

to understanding its water relationships. Robertson

and others (1972) describe big sagebrush as a phreatophyte that is a deep-rooted plant that can meet some

of its water needs from the water table or from a layer

of soil just above the water table. In soils without

restricting layers, root depths for basin big sagebrush

(many of Daubenmire’s [1975] basin big sagebrush

stands are probable Wyoming big sagebrush stands;

McArthur and Sanderson 1999) have been recorded as

deep as 10 feet (3 m) (Daubenmire 1975). For mountain and Wyoming big sagebrush, depths from 5 to 8

feet (1.5 to 2.5 m) have been reported (Daddy and

others 1988; Manning and Groeneveld 1990; Sturges

1977b, 1979; Welch 1997). The tap root of individual

big sagebrush plants is not necessarily the deepest.

Often, the deepest roots are branches off of the tap root

(Manning and Groeneveld 1990; Sturges 1977b). Not

only does big sagebrush produce a deep root system,

but just under the soil surface lateral roots branch off

the tap root forming a vast root network; the majority

of the root system occurs just 12 inches (30.48 cm)

under the soil surface and under the canopy of big

sagebrush plants (Daddy and others 1988; Flanagan

and others 1992; Leffler and others 2004; Manning

and Groeneveld 1990; Sturges 1977b, 1979). These

shallow roots not only absorb water that accumulates

in the upper soil layers during winter and spring but

can also make use of infrequent moisture from summer

convective storms (Donovan and Ehleringer 1994;

Leffler and others 2004). Some of these lateral roots

extend out from mature plants a distance of 3 to 5 feet

(1 to1.53 m) before growing deeper into the soil profile

(Sturges 1977b; Welch 1997). Thus, big sagebrush

develops a two-tiered root system of dense root network at the soil surface and a deep system with tap

root or extending laterals. Root growth begins in the

early spring a few days before shoot or stem growth

and continues through the late fall (Fernandez and

Caldwell 1975; Robertson 1943; Sturges 1979).

Leaf development in big sagebrush is dimorphic,

that is, two kinds of leaves—ephemeral and persistent—are produced during the coarse of the growing

season (Branson and others 1976; Daubenmire 1975;

Link and others 1995; Miller and others 1983, 1986;

Miller and Shultz 1987). Diettert (1938) noted the two

types of leaves and the timing of their development but

did not differentiate them by name. Big sagebrush

plants start the growing season in early spring with

just persistent leaves that were formed during the

pervious growing season; however, early in the current growing season large ephemeral leaves develop

(Miller and Shultz 1987). After the first crop of ephemeral leaves have matured, a second crop of smaller

ephemeral leaves and persistent leaves start to develop in the axes of the mature ephemeral leaves

producing what is termed a short shoot. There are, at

this point, actually four kinds of leaves: (1) the persistent leaves that overwintered, (2) large mature ephemeral leaves, (3) ephemeral leaves developing on short

shoots, and (4) current crop of persistent leaves also

developing on short shoots. Ephemeral leaves on inflorescences are not borne on short shoots. Miller and

Shultz (1987) noted that persistent leaves live a total

of 12 to 13 months. Miller and Shultz (1987, p. 228)

described the longevity of big sagebrush leaves: “At

the onset of drought, both the previous season perennial and large, early-developing ephemeral leaves

begin to senesce. Later developing ephemerals, including nonlobed leaves, persist during the initial

phase of leaf fall, senescing in late summer and fall. By

November only the current crop of perennial leaves

persists.” They estimated that big sagebrush maintained 33 percent of their leaves in the winter. Branson

and others (1976) estimated greater than 20 percent.

Water relations, whether plant or soil, are expressed

in terms of water potential. The guiding principle is

that water moves from a region of higher water potential to a region of lesser water potential. Water potential is expressed in bars for early literature or in

megapascals for later literature. Both units are expressed as negative values; the less negative the

higher the water potential or the more negative the

lower water potential. In other terms, water moves

from a region of higher water concentration to a region

of lower water concentration.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 137

Water use pattern of big sagebrush and soil moisture patterns have been described by a number of

workers (Anderson and others 1987; Branson and

others 1976; Branson and Shown 1975; Campbell and

Harris 1977; Carpenter and West 1989; Donovan and

Ehleringer 1994; Kolb and Sperry 1999; Link and

others 1995; Matzner and Richards 1996; McArthur

and others 1998; Miller and others 1983, 1986; Rawls

and others 1973; Shumar and Anderson 1986; Sturges

1977b, 1980). Comparisons of water relationships

among subspecies of big sagebrush are discussed in

chapter V on big sagebrush genetics (Kolb and Sperry

1999; McArthur and others 1998; Miller and others

1983, 1986; Shumar and Anderson 1986).

In general, the water use pattern of big sagebrush

begins in the late winter or early spring where water

potentials of plants (–1.3MPa) and soil (–0.03 MPa)

are at their maximum (Miller and others 1986). Of

course, climatic conditions or wet or dry years would

have a major influence on these maximum water

potentials (Anderson and others 1987; Campbell and

Harris 1977; Miller and others 1986). During this time

of maximum water potential, roots expand and the

first and largest set of ephemeral leaves develop (Miller

and Shultz 1987). As the growing season progresses,

the first set of ephemeral leaves matures, and the

short shoots with their second but smaller set of

ephemeral leaves and set of persistent leaves develop,

and roots continue to grow (Miller and others 1986).

Drought, however, can severely limit the production of

leaves (Rickard and Warren 1981). Water demands at

this time are mostly supplied from the top 10 inches of

the soil near the trunk of the plant, but as the season

progresses, soil water potential becomes less, and

water is absorbed by the big sagebrush plant in an

outward and downward direction (Sturges 1977a). By

early summer, with plants’ water potential about –3.0

MPa and soil water potential below –0.20 MPa, vegetative growth is terminated and reproductive

growth—inflorescences—starts (Miller and others

1986; Shumar and Anderson 1986). As the seasonal

drought of midsummer approaches, first and second

sets of ephemeral leaves and last year’s persistent

leaves start to senesce, followed soon by leaf abscission. Miller and others (1986) estimated that 53 percent of total leaf biomass is lost during the midsummer

drought. But in spite of hot temperatures, low soil

water, and low internal plant water potentials (–5.0

MPa), inflorescences keep on growing and maturing,

and by late fall-early winter become leafless, dried

out—senescent—with mature seeds (Daubenmire

1975; Evans and others 1992).

How does big sagebrush support reproductive growth

or growth of inflorescences during the driest part of the

year? First, water is conserved by terminating vegetative growth, reducing leaf biomass more than 50

percent, and reducing stomata conductance. Second,

the growth and maintenance of a deep root system is

able to extract available water deep in the soil profile

when available water has been exhausted in the upper

portion of soil profile (Rickard 1985). Last, big sagebrush has the ability to decrease osmotic potential,

thus maintaining turgor pressure above 0 MPa (Evans

and others 1992). Evans and others (1992) concluded

that this decrease is not due to osmotic adjustment

(accumulation of solutes in big sagebrush cells). They

found that leaf water volumes decreased by 75 percent, which would in effect concentrate, in a passive

manner, solutes within the leaves. This, coupled with

elastic cell walls (Evans and others 1992), would

maintain turgor pressures above 0 Mpa. They noted

the accumulation of proline (a free amino acid) and

cyclitol (a sugar alcohol) in leaves; both compounds

would help to maintain turgor pressure and protect

enzymes of water-stressed cells. All these factors taken

together allow big sagebrush to tolerate drought while

actively supporting inflorescence growth. However,

another factor called hydraulic lift may play a role in

the support of growing inflorescences and drought

tolerance.

Hydraulic Lift

Roots often pass through dry soil to soil that contains

more water, and drier soil’s water potential can be

more negative than root water potential; this sets up

the possibility of water movement out of roots and into

soil (Richards and others 1987). Richards and Caldwell

(1987), studying the daily fluctuation of soil water

potential of the upper layers of soil (35, 50, and 80 cm)

beneath the canopy of big sagebrush, found that soil

water potential was greater at night and less during

the day. When they suppressed transpiration, soil

water potential of the upper soil layers increased

steadily, both day and night, throughout the 3-day

experiment. They concluded from their soil water potential data and experimental results that “at night

water absorbed from moist soil by deeper roots is

transported to and lost from roots into drier upper soil

layers.” They termed this phenomenon “hydraulic lift.”

Additional evidence for hydraulic lift comes from a

study by Caldwell and Richards (1989) who treated big

sagebrush roots at depths of about 4 feet (1.2 m) with

deuterated water and found deuterated water appearing in the stem water of neighboring grass plants. Not

only did this experiment support the hydraulic lift

hypothesis but also raised the possibility of parasitism

of water stored in the upper soil layers by neighboring

plant roots. Later, Ryel and others (2002) reported

that parasitism of water from hydraulic lift could

increase transpiration of non big sagebrush plants by

20.5 percent.
138 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Caldwell (1990) noted, concerning the ecological

implication of hydraulic lift:

Several benefits of hydraulic lift have been suggested,

including maintenance of active fine roots in the upper

drier soil layers and facilitation of nutrient uptake in

these layers (Richards & Caldwell, 1987; Caldwell et al.

1991). It has been demonstrated that hydraulic lift can

improve the effectiveness of water uptake by the sparse

deep root system by allowing the plant to temporarily

store water in the upper soil layers at night. Thus, the

deep roots can continue to absorb water 24 hours per

day and thereby increase their effectiveness. The evidence supporting this concept was an appreciable reduction (25 to 50 percent) of transpiration on days

following circumvention of hydraulic lift by nighttime

illumination (Caldwell & Richards, 1989). Despite the

advantages of hydraulic lift, if water is released into the

soil in the proximity of neighboring plant roots, some of

this moisture might be forfeited to water parasitism by

neighbors.

In addition, water from hydraulic lift should prolong

the activity of soil microorganisms, especially those of

the rhizoshphere, which in turn should aid nutrient

uptake in the upper soil zone where nutrients are more

concentrated (Caldwell and others 1991b; Matzner

and Richards 1996).

Big Sagebrush Water Potentials

Compared to Other Plant Species

Comparisons of big sagebrush water potentials to

other plant species are given in table 4.17. Values

sharing the same author or authors and year are

comparable. For example, the Dina and others (1973)

report shows that big sagebrush experiences the least

plant water potential (–70.3 bars) or greater water

stress than the other plant species studied. But in the

Branson and others (1976) report, six out of 10 species

studied experienced less plant water potential (–79 to

–103 bars) or greater water stress than big sagebrush.

Everett and others (1977, p. 274) noted, “Water potentials of big sagebrush and shadscale were significantly

(0.5) lower than those of rabbitbrush or galleta grass

in the same community.” Big sagebrush, unlike a

number of plant species, does not undergo osmotic

adjustment to maintain turgor pressure with drying

soils but adjusts through the reduction of cellular

water and cell wall elasticity and the accumulation of

proline and cyclitol (Evans and others 1992).

Like other plants, big sagebrush intercepts rainfall

and snowfall. Hull (1972, p. 65) found that “sagebrush

intercepts both rain and snow, and that both evaporate from the plant surface without getting to the soil.

Thus, an overlooked and undesirable feature of big

sagebrush is that it prevents rain and snow from

replenishing the soil moisture and thus reduces yields

of associated grasses.” Would not grass, forb, and

nonsagebrush shrubs also intercept rainfall and snowfall and “prevent replenishing soil moisture” to some

degree? Hull (1972) noted that wheatgrass growing in

the open had an average root depth of 60 inches

compared to 39 inches when growing with sagebrush.

West and Gifford (1976) estimated that for an entire

big sagebrush community the amount of total annual

rainfall, excluding snowfall, intercepted by the plants

to be 4 percent.

Hutchison (1965) compared snow accumulation and

disappearance in big sagebrush and grass study plots.

He found more snow accumulation, hence more water,

in the big sagebrush plots than in the grass-covered

plots (also see Sturges 1977a, 1979). During snowmelt, the grass plots formed a continuous layer of ice,

which prevented some of the meltwater from entering

the soil beneath the grass plots, resulting in earlier

peak flows and incomplete soil moisture recharge. A

continuous layer of ice did not form on the big sagebrush plots, thus meltwater would have a better chance

of recharging soil moisture.

Gifford and Busby (1974) noted in their study that

water infiltration rates for big sagebrush sites that

were disturbed by plowing or grazing were lower than

undisturbed sites, resulting in greater sediment production on disturbed sites than the undisturbed big

sagebrush site. Lusby (1979) noted just the opposite in

his study.

Ryel and others (2003) compared the pattern of

water movement into soils following rain events, between basin big sagebrush plots and bared soil plots.

They (p. 757) observed: “Rainwater was moved rapidly

downward shortly after the rain event and continued

over a period of a few days. For rainwater reaching a

0.3-1.5 m depth, the portion redistributed by roots was

estimated to range from 100% for small rainfall events

(<8 mm) to 74% for a 36 mm event.” This process is

termed hydraulic redistribution. They found that during the fall-spring soil recharge period, 67 percent of

all water movement downward below 0.1 m was by the

root system and 87 percent below 0.3 m level.

Anderson and others (1987) conducted a study to

determine the ability of monocultural stands of crested

wheatgrass (Agropyron desertorum), giant wildrye

(Leymus cinereus), streambank wheatgrass (Elymus

lancealatus), Wyoming big sagebrush, and natural big

sagebrush steppe vegetation to deplete water from a

clay-loam soil. The problem they were investigating

was the intrusion of water into the zone where hazardous materials were buried. Their objectives were to

determine the water use pattern of different vegetative cover and select which cover would best prevent

the intrusion of water into hazardous waste zones.

They concluded that for their study site at the Idaho

National Engineering Laboratory Field Station a

monocultural stand of any of three perennial grasses

or Wyoming big sagebrush would prevent intrusion

of water into hazardous waste zone of soil 1.4 m deep

and that the native community would also prevent

intrusion.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 139

Table 4.17—Comparisons of plant water potentials of big sagebrush to other plant

species.Data expressed as megapascals (Mpa) or bars.Bars can be

coverted to Mpa by multiplying bars by 105

Pa.Values sharing the same

author or authors and year are comparable.

Species Plant water potential Source

Antelope bitterbrush (Purshia tridentata)

–5.5 to –45.5 bars Dina and others 1973

Big sagebrush (Artemisia tridentata)

–8.3 to –70.3 bars Dina and others 1973

–0.95 to –2.99 Mpa Drivas and Everett 1987

–0.80 to –2.10 Mpa Evans and Ehleringer 1994

–1.10 to 1.70 Mpa Romo and Haferkamp 1988

–2.00 to –3.00 Mpa Drivas and Everett 1988

–5.00 Mpa Delucia and Heckathorn 1989

–2.00 to –3.30 Mpa Link and others 1995

–4.00 to –4.50 Mpa Romo and Haferkamp 1989

–20 to –66 bars Branson and others 1976

–55 to –60 bars Branson and others 1967

Bigtooth maple (Acer grandidentatum)

–4.5 to –33.1 bars Dina and others 1973

Creeping barberry (Berberis repens)

–9.0 to –35.7 bars Dina and others 1973

Gambel oak (Quercus gambelii)

–9.7 to –45.5 bars Dina and others 1973

Greasewood (Sarcobatus vermiculatus)

–29 to –64 bars Branson and others 1976

–52 to –70 bars Branson and others 1967

–3.50 to –3.80 Mpa Romo and Haferkamp 1989

Green rabbitbrush (Chrysothamnus greenei)

–29 to –85 bars Branson and others 1976

Horsebrush (Tetradymia spinosa)

–28 to –50 bars Branson and others 1976

Mat saltbush (Atriplex corrugata)

–32 to –96 bars Branson and others 1976

Nuttall saltbush (Atriplex nuttallii)

–32 to –103 bars Branson and others 1976

–83 to –94 bars Branson and others 1967

Pinyon pine (Pinus edulis)

–0.80 to –2.10 Mpa Evans and Ehleringer 1994

Ponderosa pine (Pinus ponderosa)

–2.50 Mpa Delucia and Heckathorn 1989

Prostrate kochia (Kochia prostrata)

–1.30 to –2.10 Mpa Romo and Haferkamp 1988

Rubber rabbitbrush (Chrysothamnus nauseosus)

–0.70 to –0.70 Mpa Evans and Ehleringer 1994

–20 to –41 bars Branson and others 1976

Shadscale (Atriplex confertifolia)

–23 to –94 bars Branson and others 1976

Singleleaf pinyon (Pinus monophylla)

–1.10 to –2.02 Mpa Drivas and Everett 1987

–1.50 to –2.50 Mpa Drivas and Everett 1988

Silver sagebrush (Artemisia cana)

–42 bars Branson and others 1967

Spiny hopsage (Grayia spinosa)

–2.00 to –6.20 Mpa Link and others 1995

–32 to –79 bars Branson and others 1976

Utah juniper (Juniperus osteosperma)

–0.80 to –2.80 Mpa Evans and Ehleringer 1994

Water birch (Betula occidentalis)

–3.8 to –22.3 bars Dina and others 1973

Winterfat (Eurotia lanata)

–31 to –91 bars Branson and others 1976
140 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Global Warming

Concerns over possible warming of the Earth’s atmosphere, due to rising levels of atmospheric CO2 and

other greenhouse gases from burning of fossil fuels

and other human activities, has stimulated research

on effects of global warming on big sagebrush (Harte

and Shaw 1995; Johnson and Lincoln 1990, 1991; Loik

and Harte 1996; Miller and others 1991a; Perfors and

others 2003; Shaw and others 2000). Although dry-wet

cycles and cooling-warming cycles are not new, the

consensus among the cited authors is that big sagebrush would be favored by global warming. Miller and

others (1991a) point out that big sagebrush, like other

plants, reduces its biomass output during a drought

but has the ability to recover quickly. Miller and

others (1991a, p. 8) predict: “If an accelerated warming trend does occur in the Great Basin (Global Warming), accompanied with a decrease in precipitation, we

can expect, based on past events, an increase in dominance of woody plants, a decrease in total plant cover

and an increase in soil erosion.” Medin and Anderson

(1979) noted that during drought big sagebrush was a

more dependable forage for mule deer than other

species studied. Studying the effects of heated plots

across a soil moisture gradient, Harte and Shaw (1995)

found that big sagebrush biomass increases in the

drier habits and an enhancement of big sagebrush

seedling establishment in the heated plots. They suggested that global warming would change the dominant vegetation of a meadow habitat toward big sagebrush. Perfors and others (2003) observed: “Our

findings suggest that global climate change [warming]

will result in increased growth and range expansion of

sagebrush near northern or high-elevation range

boundaries in the Western United States.”

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Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis:

Asteraceae). Biochemical Systematics and Ecology. 20: 53–67.

Winward, Al H. 1991. A renewed commitment to management of

sagebrush grasslands. In: Research in rangeland management.

Special Rep. 880. Corvallis: Oregon State University, Oregon

Agriculture Experimental Station: 2–7.

Yorks, Terence P.; West, Neil E.; Capels, Kathleen M. 1992. Vegetation differences in desert shrublands of western Utah’s Pine

Valley between 1933 and 1989. Journal of Range Management.

45: 569–578.
148 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Notes

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 149

Chapter

V

Big Sagebrush Genetics

This chapter covers chromosome number, polyploid level, hybridization, variability of

a host of characteristics (chromatographic profiles, monoterpenoids, digestibility, preference, protein, biomass, germination) selection, and breeding of big sagebrush.

Chromosome Number _____________________________________________

For eukaryotic organisms such as big sagebrush, the chromosomes are the structures

within the nucleus that carry the genes. Chromosomes are the chemical blueprint of life.

Each chromosome is made up of a long linear deoxyribonucleic acid molecule (DNA) and

appears as threads or contracted rods of chromatin during mitosis and meiosis. DNA is

composed of four units called nucleotides; and each nucleotide is in turn made up of three

molecules—phosphate, deoxyribose sugar, and one of four nitrogenous bases (thymine,

cytosine, adenine, and guanine). The pairing of the nitrogenous bases among the four

types of nucleotides—adenine-thymine, guanine-cytosine—is responsible for the double

helix configuration of DNA molecule, its replication, and its ability to carry genes or

segments that encode ribonucleic acid (RNA) molecules, which in turn are responsible

for protein synthesis necessary for the orderly development and well-being of organisms

(Fairbanks and Andersen 1999; Raven and others 1999; Solbrig 1972).

The continuity of life is a major function of chromosomes. This is achieved by selfreplication of the DNA molecules during the interphase of mitosis and meiosis and

separation of whole chromosomes into daughter cells or passing of these replicates from

parent to offspring as gametes (Fairbanks and Andersen 1999; Raven and others 1999;

Solbrig 1972).

Orientation of homologous chromosomes on the spindle equator during metaphase I

of meiosis I with respect to paternal- versus maternal-derived chromosomes is random,

or in other words, nonhomologous chromosomes sort independently into the two

daughter cells. This results in a large number of chromosomal combinations that can be

calculated from the formula 2n , where n equals the haploid chromosome number. For

example, if an organism’s haploid chromosome number is 9, the chromosomal combinations for the gametes would be 512. Chromosomal recombination to form gametes is an

important source of variability or genetic recombination within a species but is not the

only source. During prophase I of meiosis I, when homologous chromosomes are paired,

nonsister chromatids can exchange segments in a process referred to as “crossing over.”

This is yet an additional source of an organism’s variability or genetic recombination
150 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

(Fairbanks and Andersen 1999; Raven and others

1999; Solbrig 1972). Mutations and changes in ploidy

are other sources of genetic recombination.

The haploid chromosome number “n”—due to presence of two ploidy levels, “x” is the proper term—of big

sagebrush has been intensively studied (Barker and

McKell 1986; Diettert 1938; Kelsey and others 1975;

McArthur 1989; McArthur and others 1979, 1981;

McArthur and Sanderson 1999; McArthur and Welch

1982; Sanderson and others 1989; Stahevitch and

Wojtas 1988; Taylor and Brockman 1966; Taylor and

others 1964; Ward 1953). The results of all these

studies agree that the base number of chromosomes

for big sagebrush is 9 (n = x = 9; fig. 5.1). Two levels of

ploidy have been reported among the three common

subspecies of big sagebrush—diploid and tetraploid

2n = 2x = 18 (fig. 5.2) and 2n = 4x = 36 (fig. 5.3) (Barker

and McKell 1986; Diettert 1938; Kelsey and others

1975; McArthur and others 1979, 1981; McArthur and

Sanderson 1999; Sanderson and others 1989;

Stahevitch and Wojtas 1988; Taylor and Brockman

1966; Taylor and others 1964; Ward 1953).

Polyploidy _____________________

“Polyploidy” is the term used to describe species that

have three or more complete chromosome sets in

somatic cells (Fairbanks and Andersen 1999; McArthur

1989). Polyploidy is the driving force in the evolutionary development of many species of flowering plants.

Figure 5.1—Big sagebrush chromosomes (meiosis,

metaphase I) haploid n = x = 9 (photo by E. Durant McArthur).

Figure 5.2—Big sagebrush chromosomes (mitosis, metaphase) diploid 2n = 2x = 18 (photo by

E. Durant McArthur).

Figure 5.3—Big sagebrush chromosomes (mitosis, metaphase) tetraploid 2n = 4x = 36 (photo by

E. Durant McArthur).

It has been estimated that from 47 to over 70 percent

of flowering plants are polyploid (Raven and others

1999). For big sagebrush, tetraploidy is the highest

common level of ploidy known to date, although higher

levels are known but rare (McArthur and others 1979;

McArthur and Sanderson 1999). Tetraploid zygotes

can be produced by the union of two unreduced gametes from diploid plants. Also, tetraploids can be

produced by a process called endoploidy. Here a somatic cell of a diploid plant replicates its chromosomes

but fails to go through cytokinesis and in turn replicate its chromosomes a second time. Next, division is

finished by cytokinesis. The resultant daughter cells
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 151

have two complete sets of chromosomes. Continued

mitotic division by these daughter cells could produce

a sector of plant tissues that would be entirely composed of tetraploid cells. If this sector developed into

flowers, gametes produced from such flowers would be

diploids, and self-fertilization would produce tetraploid seeds (Fairbanks and Andersen 1999).

All three subspecies of big sagebrush (Artemisia

tridentata ssp. tridentata—basin big sagebrush, A. t.

ssp. vasyana—mountain big sagebrush, and A. t. ssp.

wyomingensis—Wyoming big sagebrush) contain polyploid populations (McArthur and Sanderson 1999).

Wyoming big sagebrush appears to be uniformly tetraploid (4x = 36), that is, all populations examined to

date were tetraploids (Barker and McKell 1986;

McArthur and others 1979, 1981; McArthur and

Sanderson 1999; Sanderson and others 1989). Basin

and mountain big sagebrush are of mixed ploidy levels

having both diploid and tetraploid populations

(McArthur and Sanderson 1999). McArthur and

Sanderson (1999, p. 1767) stated about 75 percent of

the basin big sagebrush populations studied were

diploid; however, tetraploid “populations are scattered throughout the range with notable pockets in

north-central Washington extending into south-central British Columbia and in southern California.” For

mountain big sagebrush, about 70 percent of the

populations studied are diploid with tetraploids scattered throughout its range, although McArthur and

Sanderson (1999, p1767) noted “4x populations have

not been discovered in the Colorado Rockies or southcentral British Columbia.”

Knowing the chromosome number of a species is

important from two points of view: chromosome number can give an indication of breeding or hybridization

compatibility, and it can indicate the degree of genetic

recombination potential. For example, a cross between a diploid and a tetraploid would produce a

sterile triploid. Odd ploidy level plants are sterile

because it is not possible during meiosis to divide an

odd number of chromosome sets equally into complete

euploid sets, or in other words, cannot produce balance

gametes from an odd number of chromosomes

(Fairbanks and Andersen 1999). The number of genetic recombination increases from 512 for diploids

plants such as big sagebrush that have a chromosome

set of 9, to 262,144 for tetraploids plants with a

chromosome set of 18. Tetraploids should express

greater genetic diversity and perhaps greater adaptation. However, the expected variation is damped by

polyploid chromosome segregation (McArthur 1989).

McArthur and others (1981, 1998b) give strong evidences that big sagebrush is autopolyploid as opposed

to allopolyploid. Autopolyploid plants are derived from

the same ancestral diploid species, whereas allopolyploid plants are derived from different ancestral

diploid species. Tetraploids plants derived from the

process of autopolyploidy should be morphologically

similar to the diploid plants. Also, their chromosomes

morphology or karyotype should be similar. Tetraploid plants derived from allopolyploidy would look

different (Fairbanks and Andersen 1999). McArthur

and others (1981, p.589) cite the following evidence for

autopolyploidy in big sagebrush: “morphologically indistinguishable 2x and 4x plants, a few mixed ploidy

populations, consistent formation of IVs in 4x PMCs,

a relatively uniform 2x karyotype, which is twice the

2x one.”

Ward (1953) observed that tetraploid big sagebrush

plants were limited to the poorer, rockier soils and

were smaller, slower growing plants than the diploid

big sagebrush plants. Recently, Barker and McKell

(1983), McArthur and Sanderson (1999), and

Sanderson and others (1989) have noted that diploids

of basin and mountain big sagebrush do grow faster

and are generally larger plants, and they grow in

wetter habitats than the tetraploids of Wyoming big

sagebrush (more on this in a later section of this

chapter). However, there is some evidence that

tetraploids of basin big sagebrush are smaller plants

than diploids and are more readily eaten by domestic

sheep (Ovis aries) (McArthur and Welch 1982; Welch

and others 1987).

Kelsey and others (1975) studied chromosome numbers of mountain big sagebrush as related to three

sesquiterpene lactone races. These three races were:

Hot Spring, which produced five sesquiterpene lactones (arbusculin-A,-B,-C; rothin-A, -B; high-elevation, which produced two (artevasin, dehydroleucodin);

and low-elevation, which produced three (arbusculin -

A, -B, -C). Kelsey and others (1975, p. 209) concluded

that “there appears to be no correlation between chromosome numbers and sesquiterpene lactone races.”

They did present data that demonstrated the exchange of genetic material among sesquiterpene lactone races and that this exchange is mainly restricted

to narrow zones of sympatry.

Hybridization ___________________

Ward (1953, p. 170) in his study of basin and mountain big sagebrush stated, “It should be pointed out

that we have been comparing here only the extremes

and that all degrees of intermediacy may be found.”

This observation of intermediacy is a hint that subspecies of big sagebrush can hybridize, although at this

time, only two subspecies of big sagebrush were recognized—basin and mountain. Later, Beetle (1960) found

what he believed were natural crosses between basin

and mountain big sagebrush. Hanks and others (1973)

reported chromatographic evidences of natural hybridization occurring between mountain and basin big
152 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

sagebrush and between these two subspecies of big

sagebrush and other Artemisia species. McArthur and

others (1979) describe big sagebrush as a highly polymorphic, wind-pollinated species, with numerous

ecotypes and biotypes that readily cross both

intraspecifically and interspecifically. However, they

felt their hybridizing data were more suggestive than

definitive.

A more definitive way of identifying hybrids between basin and mountain big sagebrush was discovered by Taylor and others (1964). They found that

seeds of mountain big sagebrush, when soaked in

water, would fluoresce brightly when exposed to longwave ultraviolet light, and seeds of basin big sagebrush do not fluoresce or do so only slightly. Others

have extended this observation to crushed leaves

soaked in water, methanol, or ethanol (Stevens and

McArthur 1974; Winward and Tisdale 1969; Young

1965). The molecules responsible for this fluoresce

have been identified as coumarins (Brown and others

1975; Shafizadeh and Melnikoff 1970) (for more information see chapter IV). However, soaking crushed

leaves in methanol or ethanol resulted in blue fluoresce for mountain big sagebrush and red or brownish

red for basin big sagebrush (Winward and Tisdale

1969; Young 1965). Regardless of the solvent used, the

technique of crushing two or three leaves in water or

alcohol and exposing the mixture to long-wave ultraviolet light provides a genetic marker to separate

mountain and basin big sagebrush or to identify hybrids between the two (fig. 5.4).

Noller and McArthur (1986) were the first to use the

fluoresce test to identify hybrids resulting from artificial hybridization between basin and mountain big

sagebrush. They crossed an accession of basin big

sagebrush from Dove Creek, CO, with an accession of

mountain big sagebrush from Hobble Creek, UT (near

Springville). Dove Creek was used as the maternal

line and Hobble Creek was the paternal line. Seeds

were collected from the maternal line. Because the

maternal line does not contain coumarin compounds

that fluoresce under ultraviolet light, seedlings that

do are the result of hybridization between Hobble

Creek and Dove Creek accessions. Hybridization was

accomplished by collecting pollen from onsite Hobble

Creek mountain big sagebrush plants and transferring this pollen to white pollination bags attached to

Dove Creek plants prior to flower opening. The maternal line was established several years ago in a uniform

garden located at Ephraim, UT, about 56 miles south

of the Hobble Creek site. Seedlings from the maternal

line with the highest fluorescence were selected for a

mass selection garden.

From this mass selection garden, McArthur and

others (1988) reported several lines of evidences that

seedlings collected from the maternal line were intermediates between paternal and maternal parents

(tables 5.1 and 5.2). Coumarin content of hybrids as

measured by percent transmittance—that is the higher

the transmittance the lower the concentration of

coumarins—were intermediate of the parental lines,

69 versus 54 and 86 percent (table 5.1). Methacrolein

content of hybrids was also intermediate of the parental lines as well as camphor, camphene, 1,8 cineole, bthujone, unknown monoterpenoid labeled as unknown

1, and total monoterpenoids (table 5.2). All these

measurements are evidence that the seedlings selected from the maternal line were hybrids and verified that hybridization between basin and mountain

big sagebrush could be achieved through artificial

means.

From this same study, McArthur and others (1988)

recorded evidence of natural hybridization between a

stand of basin and mountain big sagebrush located in

Diamond Fork Canyon, Utah County, UT, about 11

miles southeast of Spanish Fork. There, mountain big

Figure. 5.4—Fluorescing of coumarin compounds

leaching from crushed leaves of mountain big sagebrush into water exposed to long-wave ultraviolet

light. Test tube on left contains crushed leaves of

basin big sagebrush that does not leach coumarin

compounds (photo by Bruce L. Welch).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 153

Table 5.1—Amount of fluorescence produced by maternal and

paternal lines of big sagebrush and their putative

hybrid. The maternal line was an accession of

basin big sagebrush (Artemisia tridentata ssp.

tridentata) collected from Dove Creek, CO, and the

paternal line was an accession of mountain big

sagebrush (A. t. ssp. vaseyana) collected at the

mouth of Hobble Creek Canyon near Springville,

UT. Data are expressed in terms of percentage of

transmittance, or in other words, the greater the

fluorescence the less light that will pass through

the sample and the lower the transmittance. Data

from McArthur and others (1988).

Percentage of transmittance1

Dove Creek maternal line 85.6 ± 1.3a

Putative hybrid 69.1 ±.9b

Hobble Creek paternal line 54.0 ± 6.3c

1 Means and standard error of the means. Values sharing the same

superscripts are not significantly different at the (p <.01) StudentNewman- Keuls means comparison test.

Table 5.2—Monoterpenoid profiles of the maternal and paternal lines in the production of a hybrid line. The maternal line was an accession of basin big

sagebrush (Artemisia tridentata ssp. tridentata) collected from Dove

Creek, CO, and the paternal line was an accession of mountain big

sagebrush (A. t. ssp. vaseyana) collected at the mouth of Hobble Creek

Canyon near Springville, UT. Individual monoterpenoids data are expressed in relative terms to the total monoterpenoid content, which is a

percentage of the total. Total percent of monoterpenoids are expressed

on a dry-weight basis. Data from McArthur and others (1988).

Monoterpenoids Dove Creek Putative hybrid ‘Hobble Creek’

Methacroleina 9.0 ± 1.1b 4.2 ± .5 —

a-pinene — 0.7 ± .2 1.9 ± 10.8

Camphene — 1.4 ± .4 6.1 ± 1.5

1,8 cineole — 2.1 ± .7 16.0 ± 4.7

Unknown 1 27.0 ± 4.6 18.6 ± 2.7 —

Unknown 2 1.1 ± .6 Trace —

b-thujone 56.2 ± 3.8 25.5 ± 3.8 4.7 ± 2.5

Unknown 4c 2.2 ± .9 21.4 ± 3.5 —

Camphor 2.2 ± 1.1 22.8 ± 2.7 59.2 ± 7.1

Unknown 5 — — 4.7 ± 2.6

Unknown 6 2.2 ± 1.1 2.8 ± .6 4.0 ± 2.9

Unknown 7 — 1.4 ± .3 4.1 ± 2.5

Total percent dry weight 0.91 ± .07 1.47 ± 1.0 2.15 ± .17

a

Not a monoterpenoid.

b

Means and standard error.

c

Unknown 3 is listed in table 7 of the McArthur and others (1988) report but is not pertinent

to the above data set.

sagebrush grows on a bench and basin big sagebrush

near the canyon floor or valley bottom. Separating

these two subspecies is a narrow zone or a 250-foot

hillside that supports a population of big sagebrush

that appears to be an intermediate between the two

subspecies. As with artificial hybridization, these natural hybrids were intermediate, for the same chemical

characteristics described earlier, of mountain and

basin big sagebrush (also see Byrd and others 1999).

Narrow hybrid zones between mountain and basin

big sagebrush have been studied at three additional

sites: Orem, UT; Salt Creek Canyon east of Nephi, UT;

and Clear Creek Canyon west of Richfield, UT (Freeman and others 1991; Wang and others 1998). All

three zones were reported as producing stable hybrids

that expressed intermediate characteristics of the

parental subspecies (Freeman and others 1995; Wang

and others 1998).

Graham and others (1995, p. 709) noted, “Stable

hybrid zones are inconsistent with the classical theory

of speciation.” The classical theory of speciation holds

that when two populations come into contact, they
154 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

either remain reproductively isolated, or the populations fuse into one (Graham and others 1995). If,

indeed, these zones of hybridization form a stable

hybrid and are not an artifact of short-term observations, then the factor responsible for hybrid zone

stabilization is either endogenous or exogenous in

nature (Wang and others 1997).

Wang and others (1997, p. 95) explain these two

possibilities. First, endogenous factors: “The ecologically neutral dynamic equilibrium model postulates

that hybridization disrupts coadapted gene complexes,

causing developmental and physiological problems

that reduce the fitness of hybrids. Thus, in this model,

selection results solely from internal genetic factors

and hence is endogenous.” Second, exogenous factors:

“In contrast, the ecologically dependent bounded hybrid superiority model assumes that the selection

stabilizing hybrid zones is due to genotype by environment interactions, and occurs because of environmental heterogeneity. Specifically, this model assumes

that hybrids should be more fit than their parental

taxa within the hybrid zones, and less fit outside the

hybrid zones.”

To test the hybrid superiority model, Wang and

others (1997) conducted reciprocal transplant experiments. They found that hybrids were more fit in the

hybrid zone gardens than in either parental garden,

and paternal taxon were more fit in their respective

gardens than either the hybrids or alien parent. These

observations support the hybrid superiority model.

Earlier, a study conducted by Graham and others

(1995) found that overall fitness of hybrids in terms of

stand density and recruitment, flower, seed production, germination, and herbivore load were equal to,

and in some cases superior to, parents. Wang and

others (1997, p. 101) simply stated, “Our results do not

agree with the predictions of the dynamic equilibrium

hypothesis, which specifically predicts that heterozygotes for genes distinguishing two hybridizing taxa

should have lower fitness than either parent.”

McArthur and others (1998a) measured respiration

and water potential profiles of two parents and hybrids. Even though the three habits differed from one

another, hybrid plants’ respiratory and water potentials profiles were intermediate of the parent’s profiles, or in other words, the study showed no decreases

in adaptation within the hybrid plants. In the ninth

study of narrow hybrid zones between mountain and

basin big sagebrush, Wang and others (1999, p. 1099)

observed, “The concentrations of elements in the leaves

of site-indigenous sagebrush and the biological absorption coefficients differed significantly between the

subspecies and between either parental taxon and

hybrids.” Smith and others (2002) reported metabolic

difference among populations and subspecies of big

sagebrush from a narrow hybrid zone. These differences were expressed in reciprocal transplanted

gardens, thus supporting the fitness of the hybrids in

adapting to the uniqueness of the hybrid zone.

Not only are the parents and hybrid different chemically and morphologically, but the habitats they occupy are also different or unique (Wang and others

1998). Wang and others (1998) measured certain soil

properties within parental and hybrid zones. Properties measured were soil thickness, pH, and the concentration of a number of soil elements. Some of their data

appear in table 5.3. They found that soil thickness, pH,

and levels of certain elements differ among the three

sites. Wang and others (1998, p. 139) concluded: “The

hybrid zone soil is not just a simple blend of the two

parental habitat soils. Rather, it possesses novel characteristics found in neither parental habitat and is

more variable than the parental habitat soils.”

McArthur and others (1988) reported similar results

in an earlier study (also see Miglia and others 2004).

These observations support the hybrid superiority

model. Further support comes from the work of

Freeman and others (1999) and Freeman and others

(2001), who measured the floristic and vegetative

composition of parental sites and hybrid zones in

Clear Creek Canyon near Richfield, UT. Freeman and

others (1999, p. 487) found that:

...the species composition, proportions of annual plants,

perennial forbs and grasses, shrubs, rock, litter, bare

ground and total vegetative cover differ among the

parental sites and hybrid zone. Canonical correspondence analysis and ordination showed that the two big

sagebrush subspecies and their hybrids are each associated with different groups of species, and occupy

edaphically distinct habitats.

Table 5.3—Soil properties—soil thickness (cm), pH, elemental

concentration (mg/kg dry weight)—of a basin big

sagebrush (Artemisia tridentata ssp. tridentata)

site, a mountain big sagebrush (A. t. ssp. vaseyana)

site, and their narrow hybrid zone. Data from

Wang and others (1998)1

.

Soil properties Basin2 Hybrid Mountain

Soil thickness 37a 23b 18c

pH 7.9a 7.7a 6.9b

Ca 3,918ab 5,309c 4,602bc

K 319a 1,474c 687ab

Mg 158a 216ab 528c

Ba 20a 43bc 49bc

Fe 18ab 13b 20ab

Mo 7a 8a 15b

Na 4a 18bc 12c

Se 8a 4ab 3b

Zn 5ab 2b 1b

Cu 3a 3a 3a

1

 Not all data are given.

2 Means within rows with different superscripts are significantly

different from each other (p <.05).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 155

Autopolyploidy and a wind-pollination breeding system that allow gene flow within and among populations of big sagebrush gave this species the necessary

variability to dominate much of Western North America

before the onslaught of Euro-American settlers and

the invasion by cheatgrass (Bromus tectorum) and

other alien weed species. This breeding system has

also allowed big sagebrush to develop into at least

three subspecies that occupy different habitats. Stanton

and others (2002, p. 579) suggest: “differentiation

within the Tridentatae is the result of strong ecotypic

selection over a background of widespread hybridization.” Another possible source of genetic variability is

gene mutation, but this has not been studied in big

sagebrush. The following section covers the variability

for a number of traits and the breeding and selection

schemes that could give rise to superior forms of big

sagebrush.

Variability ______________________

Preference

During in vivo digestibility trials, Smith (1950)

noted that mule deer (Odocoileus hemionus hemionus)

showed definite aversion to individual big sagebrush

plants. This is the first evidence of differential preference of an animal for big sagebrush. Since that time, a

number of researchers have made similar observations

for a variety of animals: mule deer (Hanks and others

1971; Personius and others 1987; Sheehy and Winward

1981; Smith 1959; Wambolt 1995, 1996; Welch and

McArthur 1986b; Welch and others 1981,1983; White

and Welch 1981); elk (Cervus elaphus nelsoni) (Wambolt

1995, 1996); cattle (Bos bovine) (Hanks and others

1971); domestic sheep (Sheehy and Winward 1981;

Welch and others 1987); pygmy rabbits (Brachylagus

idahoensis) (White and others 1982); and sage grouse

(Centrocercus urophasianus) (Remington and Braun

1985; Welch and others 1988, 1991).

A study conducted by Welch and McArthur (1986b)

illustrates the variability of wintering mule deer preference for accessions and subspecies of big sagebrush.

In this study, 21 accessions of big sagebrush were

established on three uniform gardens on three mule

deer winter ranges. Ten accessions were collected

from different populations of mountain big sagebrush,

seven for basin big sagebrush and four for Wyoming

big sagebrush. Each accession was represented by 10

plants, and all 210 plants were planted at random on

a 7- by 7-foot grid. Results of the Welch and McArthur

(1986b) 3-year study are given in tables 5.4 and 5.5. All

plants, accessions, and subspecies received some mule

deer use. Wintering mule deer significantly preferred

mountain big sagebrush over Wyoming big sagebrush,

Table 5.4—Effects of subspecies, site, and year on preference

of wintering mule deer (Odocoileus hemionus

hemionus) for accessions of big sagebrush (Artemisia tridentata). Data expressed as percent of

current year’s vegetative growth eaten (3 years,

630 plants, three uniform gardens). Data from

Welch and McArthur (1986a).

Preference for subspecies

Basin1 Wyoming Mountain

32.6a2 35.3b 44.1c

Effects due to site

Salt Creek Gordon Creek Springville

30.4a1 35.0b 50.2c

Effects due to years

1980 1981 1982

31.6a1 41.7b 42.4b

1 Basin = Artemisia tridentata ssp. tridentata; Wyoming = A. t. ssp.

wyomingensis; mountain = A. t. ssp. vaseyana. 2 Means within rows sharing the same superscript are not significantly different at the 5 percent level.

and Wyoming over basin big sagebrush (table 5.4).

More big sagebrush was consumed at the Springville

site than at the Salt Creek site, and more was consumed at the Salt Creek site than at the Gordon Creek

site (table 5.4). For some reason, more big sagebrush

was consumed in 1981 and 1982 than in 1980. On an

accessional basis, Welch and McArthur (1986b, p. 284)

observed (table 5.5):

Wintering mule deer significantly preferred the Hobble

Creek accession over the other 20 accessions across all

sites and years. Overall use of the Hobble Creek accession was 57.5 percent. Use of Hobble Creek big sagebrush varies significantly among sites. At the Salt

Creek site, the Hobble Creek accession received 47.4

percent use, 52.0 percent use at Gordon Creek, and 73.0

percent use at Springville. The consistency of ranking

for preference of the Hobble Creek accession was not

present for the other accessions and further strengthens our contention that Hobble Creek is the most

preferred.

Wambolt (1996) concluded after a 10-year study

that wintering elk and mule deer preferred mountain

big sagebrush over Wyoming big sagebrush, basin big

sagebrush, and black sagebrush (A. nova). Wambolt

(1996, p. 499) further observed:

Wyoming big sagebrush (A. t. ssp. wyomingensis Beetle

and Young) was narrowly preferred (38.6%) over basin

big sagebrush (A. t. Nutt. ssp. tridentata) (30.3%).

Black sagebrush (A. t. nova Nels.) was least preferred

(17.0%). Differences in preference among taxa were

smallest during the severest winter when more elk

were present thereby increasing total sagebrush utilization. Mule deer diets averaged 52% sagebrush over

the study. Many sagebrush plants were damaged and

even killed by heavy browsing during the study.
156 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 5.5—Preference of wintering mule deer (Odocoileus hemionus hemionus) for

accessions of big sagebrush (Artemisia tridentata) grown in three uniform

gardens. Data expressed as a percent of current year’s vegetative growth

eaten. Data points for gardens represent a 3-year mean (Welch and McArthur

1986a).

Garden

Accession1 Gordon Creek Salt Creek Springville Mean2

- - - - - - - - - - - - - - - - - - - - Percent - - - - - - - - - - - - - - - - - -

Evanston (b) 25.2 18.1 41.6 28.3a

Trough Springs (w) 17.5 30.9 41.9 30.1ab

Dove Creek (b) 26.3 31.3 35.1 30.9abc

Clear Creek Canyon (b) 31.5 19.7 42.7 31.3abcd

Loa (b) 25.0 18.5 51.3 31.6abcd

Kaibab (w) 30.9 27.2 42.4 33.5abcd

Dog Valley (b) 28.6 23.6 49.1 33.8abcde

Brush Creek (b) 35.2 24.6 47.2 35.7abcde

Wingate Mesa (b) 32.5 33.9 42.8 36.4abcdef

Milford (w) 34.5 29.0 47.4 37.1bcdefg

Clear Creek Canyon (m) 34.4 25.6 55.1 38.4bcdefg

Benmore (m) 40.1 39.3 38.4 39.3bcdefg

Pinto Canyon (m) 36.8 27.8 56.2 40.3cdefg

Evanston (w) 31.1 43.8 46.3 40.4defg

Durkee Springs (m) 36.3 27.7 58.1 40.7defg

Salina Canyon (m) 40.5 29.4 55.2 41.7efg

Sardine Canyon (m) 45.8 29.9 58.0 44.6fg

Indian Peaks (m) 40.9 40.9 55.0 45.6fg

Petty Bishop’s Log (m) 46.4 33.8 57.7 46.0g

Colton (m) 43.1 37.9 60.1 47.0g

Hobble Creek (m) 52.0 47.4 73.0 57.5h

1 (b) = basin big sagebrush (Artemisia t. ssp. tridentata); (m) = mountain big sagebrush (A. t. ssp.

vaseyana); (w) = Wyoming big sagebrush (A. t. ssp. wyomingensis). 2 Means sharing the same superscript are not significantly different at the 5 percent level.

Hanks and others (1971) studied the chromatographic profile and preference of 100 populations of

big sagebrush. They described four chromatographic

profiles within mountain big sagebrush and two within

basin big sagebrush. Cattle grazing in the Jackson

Mountains in northwestern Nevada preferred mountain big sagebrush over basin big sagebrush. Cattle

utilized more than 60 percent of the current year’s

growth of mountain big sagebrush but utilized less

than 15 percent of basin big sagebrush current year’s

growth.

Welch and others (1987), using the same three

gardens as described in the wintering mule deer preference study of Welch and McArthur (1986b), studied

the utilization of big sagebrush by wintering domestic

sheep. Five range-experienced domestic sheep were

allowed to graze in the three gardens while having

continuous access to high quality alfalfa hay and 0.28

kg of rolled barley per head per day; thus, feeding on

big sagebrush was out of choice, not out of hunger.

Results of their experiment are given in table 5.6.

Accessions that were most heavily used were Kaibab,

Colton, Trough Springs, Wingate Mesa, Milford, Brush

Creek, and Hobble Creek; three Wyoming, two basin,

and two mountain big sagebrushes. Welch and others

(1987, p.113) noted that “the sheep tend to remove

significant (60 to 70%) amounts of current growth

from the more preferred accessions before removing

even small (15%) amounts of less preferred accessions.” Repeated grazing of an area may result in the

loss of preferred plants (Rodriguez and Welch 1989;

Wagstaff and Welch 1991).

Pygmy rabbits, an obligate of big sagebrush, showed

no preference for either mountain or basin big sagebrush; instead, preference was expressed at the accession or population level (White and others 1982). An

accession called Hobble Creek II was among the most

preferred.

Welch and others (1991) conducted an experiment to

determine sage grouse preference for mountain, Wyoming, and basin big sagebrush and for accessions

within subspecies. This study was carried out by

placing captured sage grouse in a cage supporting

different subspecies and accessions within subspecies
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 157

of big sagebrush. Number of bites per subspecies and

accessions within subspecies were recorded on video

tapes. Results, by order of preference, were mountain,

Wyoming, and basin big sagebrush. On an accessional

basis, Windy Ridge, a mountain big sagebrush, was

preferred over all accessions. The Hobble Creek accession, also a mountain big sagebrush, was the second

most preferred accession. The Windy Ridge accession

was collected from the Strawberry Valley area of

north-central Utah, about 225 km north by northeast

of the sage grouse capture site about 4 miles west of

Loa, UT. Welch and others (1991) had observed birds

in this area eating this accession for a number of years.

The ‘Hobble Creek’ accession was a released accession

of mountain big sagebrush for use on wintering mule

deer and domestic sheep ranges (Welch and others

1986a). ‘Hobble Creek’ was collected about 209 km

north of the sage grouse capture site. Sage grouse are

not present in the collection area; thus, sage grouse

use for this accession was unknown. The third and last

accession representing mountain big sagebrush was

Vance Reservoir. This accession was collected near the

capture site of the sage grouse used in the Welch and

others (1991) study. They had observed sage grouse

use of this accession for several years prior to their

study. If predisposing factors were playing a role in

determining sage grouse preference, then Vance

Reservoir would have been favored. The same could

have been said for the Loa accession of Wyoming big

sagebrush and the Elise accession of basin big sagebrush, but none of these accessions collected near the

capture site were among the most preferred accessions. Therefore, previous exposure did not play an

important role in determining sage grouse preference.

In summary, Welch and others (1991, p. 464) stated:

Sage grouse under the conditions of this study showed

definite preference for mountain big sagebrush and for

certain accessions within this subspecies. However,

when leaves and buds of the preferred plants became

limited, the birds shifted to lesser liked plants. This

shift was not noticeable until after analysis of the video

tapes. We concluded that the birds, while expressing

preference, are capable of shifting their eating habits.

Remington and Braun (1985) reported that wintering sage grouse in their study preferred Wyoming big

Table 5.6—Variation in the utilization of 21 big sagebrush (Artemisia tridentata) accessions by wintering domestic sheep. Plants grown in three uniform gardens.

Data expressed as percentage of current year’s growth eaten. Data from

Welch and others (1987).

Garden

Accession1 Gordon Creek Salt Creek Springville Mean2

- - - - - - - - - - - - - - - - - - - - Percent - - - - - - - - - - - - - - - - - -

Kaibab (w) 100.0 97.8 97.1 98.3a

Colton (m) 93.5 96.0 87.5 92.3a

Trough Springs (w) 96.8 85.5 91.0 91.1a

Wingate Mesa (b) 78.8 88.5 90.5 85.9ab

Milford (w) 76.8 84.5 86.7 82.7ab

Brush Creek (b) 82.5 83.5 79.0 81.7ab

Hobble Creek (m) 79.6 84.1 78.0 80.6ab

Pinto Canyon (m) 78.4 70.5 81.2 76.6b

Sardine Canyon (m) 61.3 59.6 53.5 58.1c

Petty Bishops Log (m) 42.2 48.9 55.3 48.3c

Evanston (w) 46.3 33.8 52.5 44.2cd

Indian Peaks (m) 35.1 45.9 38.3 39.8cde

Clear Creek Canyon (m) 18.7 24.6 21.6 21.6de

Benmore (m) 11.1 18.5 20.6 16.7de

Durkee Springs (m) 12.3 21.4 14.7 16.1ef

Salina Canyon (m) 9.9 12.3 10.4 10.9f

Dog Valley (b) .0 5.2 8.1 4.4f

Clear Creek Canyon (b) .0 3.9 1.7 1.9f

Evanston (b) .0 1.5 .0 .5f

Loa (b) .0 .0 .0 .0f

Dove Creek (b) .0 .0 .0 .0f

1 (b) = basin big sagebrush (Artemisia t. ssp. tridentata); (m) = mountain big sagebrush (A. t. ssp.

vaseyana); (w) = Wyoming big sagebrush (A. t. ssp. wyomingensis). 2 Means sharing the same superscript are not significantly different at the 5 percent level.
158 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

sagebrush over mountain big sagebrush. There were

significant differences in the ways the two studies

were carried out. The plants of the Welch and others

(1991) study were planted at random in a common

garden, meaning the birds had equal access to all

accessions and subspecies. A cage was built over the

garden to maintain the sage grouse. The Remington

and Braun (1985) study was conducted in the field

where the subspecies grow in different habits, such as

the bottom of draws, which may influence the movement of the birds; if so, their perceived preferential use

could be due to uneven bird distribution. Mountain big

sagebrush does not normally grow where Wyoming big

sagebrush does, so preference may become more of an

academic issue than a real issue with sage grouse,

because as Welch and others (1991) observed, the

birds are capable of shifting from preferred big sagebrush plants to lesser preferred big sagebrush plants

without any perceived problems.

Data by Graham and others (2001, table 4) show

that gall-forming insects preferred mountain big sagebrush over basin big sagebrush. For example, the gall

formed by Rhopalomyia ampullaria, a midge, induced

31.2 galls per cubic meter on basin big sagebrush

growing on its native sites verus 5,610 on mountain

big sagebrush growing on its native site. Four species

of gall-inducing insects were found forming galls on

basin big sagebrush, whereas, seven gall-inducing

insects were forming galls on mountain big sagebrush.

Only the fruitfly, Eutreta diana, formed more galls on

basin big sagebrush (2.73 per cubic meter) than on

mountain big sagebrush (0.835 per cubic meter). Welch

and McArthur (1981) and McArthur and others (1988)

showed that mountain big sagebrush contained higher

concentrations of monoterpenoids than basin big

sagebrush. Still Graham and others (2001, p. 245)

state: “The major herbivore deterrents used by Artemisia are terpenes.” How the authors square their

statement with the fact that a host of organisms feed

directly on big sagebrush and that mountain big sagebrush contains higher concentrations of terpenes is

not known (chapters II and III).

Because a number of preference studies were conducted on uniform or common gardens, or in other

words, environmental factors that could influence

preference were kept constant, any differences in

preference would be due to differences in the genetic

makeup of the accessions and or subspecies (Scholl

and others 1977; Welch and McArthur 1986b; Welch

and others 1981, 1983, 1987, 1991,1992a). The heritability of preference is unknown in big sagebrush.

Digestibility

Digestibility is an important characteristic of forage

plants such as big sagebrush. Welch and Pederson

(1981) studied winter in vitro digestibility by mule

deer inoculum of accessions and subspecies of big

sagebrush. Results of their research are given in

table 5.7. In a uniform garden, where environmental

factors were held constant, basin big sagebrush was

more digestible than mountain and Wyoming big

sagebrush. On an accession level, some accessions

were more highly digested than others. In a companion study, Welch and others (1992a) studied the winter

in vitro digestibility of 13 accessions of Wyoming big

sagebrush grown on three uniform gardens. Results of

their study are given in table 5.8. Overall, these

studies demonstrated that big sagebrush is a highly

digestible forage for wintering mule deer and that

digestibility is under genetic control.

Table 5.7—Winter in vitro digestibility among accessions and subspecies of big sagebrush

(Artemisia tridentata) grown in a uniform garden. Data expressed as percent of

digestible dry matter. Data from Welch and Pederson (1981).

Subspecies of big sagebrush Accessions of big sagetrush

Subspecies Percent digested1 Accessions2 Percent digested1

Basin 62.1a Clear Creek (b) 64.8a

Mountain 53.2b Dove Creek (b) 64.6a

Wyoming 51.4b Loa (b) 57.0b

Indian Peaks (m) 55.8b

Benmore (m) 55.2b

Kaibad (w) 54.9b

Milford (w) 54.6b

Sardine Canyon (m) 48.7bc

Trough Springs (w) 44.6c

1 Values sharing the same letter superscript in a column are not significantly different at the

5 percent level. 2 (b) = basin big sagebrush (Artemisia tridentata ssp. tridentata); (m) = mountain big sagebrush (A. t. ssp.

vaseyana); (w) = Wyoming big sagebrush (A. t. ssp. wyomingensis).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 159

Crude Protein

Winter crude protein content of dry matter is also an

important characteristic of forage plants. Welch and

McArthur (1979b) reported that some accessions grown

under uniform conditions contained significantly

higher levels of crude protein than others (table 5.9).

Thus, crude protein of big sagebrush is under genetic

control. They further noted that basin big sagebrush

(table 5.10), the least preferred by wintering mule

deer, contained higher levels of crude protein than

mountain or Wyoming big sagebrush (table 5.11).

They suggested that a high crude protein accession

might be hybridized with a highly preferred accession,

resulting in a superior form of big sagebrush. Welch

and others (1992a) noted that accessions grown within

a subspecies, such as Wyoming big sagebrush, varied

significantly in amount of winter crude protein. In

general, big sagebrush contains higher levels of winter

crude protein than most winter forages (see chapter IV

for more details).

Monoterpenoids

The postulated adverse effects that big sagebrushs’

monoterpenoids might have on mule deer digestion

and preference were proven later to be erroneous

(Welch and others 1982; Welch and Pederson 1981)

Table 5.8—Winter in vitro digestibility of 13

accessions of Wyoming big sagebrush (Artemisia tridentata ssp.

wyomingensis). Data from three

uniform gardens were pooled. Data

expressed as the percentage of

dry matter digested. Data from

Welch and others (1992a).

Accessions Percent digested1

Arco 56.6a

Squaw Butte 55.1ab

South Fredonia 53.7ab

Warren 53.7abc

Gordon Creek 52.8bcd

Oasis 51.7bcd

Brown’s Park 50.8cde

Rush Valley 50.8cde

Glenns Ferry 50.5cde

Loa 50.4de

North Kemmerer 50.1de

Daniel 47.8e

Dinosaur 47.7e

1

Means sharing the same superscript are not significantly different at the 5 percent level.

Table 5.9—Winter crude protein content of current year’s

vegetative growth among accessions of big

sagebrush (Artemisia tridentata) grown in a

uniform garden. Data expressed on a drymatter basis. Data from Welch and McArthur

(1979b) and Welch (1983).

Accessions1 Percent of crude protein2

Dove Creek (b) 16.0a

Clear Creek Canyon (b) 15.3ab

Evanston (b) 15.2b

Dog Valley (b) 14.5bc

Loa (b) 14.5bc

Big Brush Creek (b) 13.1bcd

Evanston (w) 12.9cd

Wingate Mesa (b) 12.8de

Colton (m) 12.0def

Kaibab (w) 11.9def

Clear Creek Canyon (m) 11.7def

Salina Canyon (m) 11.7def

Alton (m) 11.3efg

Milford (w) 11.2efg

Petty Bishop’s Log (m) 11.2efg

Indian Peaks (m) 11.2efg

Trough Springs (w) 11.0fg

Pinto Canyon (m) 11.0fg

Sardine Canyon (m) 10.5fg

Durkee Springs (m) 10.0a

Benmore (m) 10.0g

1 (b) = basin big sagebrush (Artemisia tridentata ssp.

tridentata); (m) = mountain big sagebrush (A. t. ssp. vaseyana);

(w) = Wyoming big sagebrush (A. t. ssp. wyomingensis). 2 Means sharing the same superscript are not significantly

different at the 5 percent level.

Table 5.10—Winter crude protein content of

three subspecies of big sagebrush—basin, mountain, and Wyoming—2-year summary. Plants

grown in a uniform garden; percentages expressed on a dry matter basis. Data from Welch and

McArthur (1979b) and Welch

(1983).

Subspecies1 Percent of crude protein2

Basin 14.5a

Wyoming 11.8b

Mountain 11.1b

1 Basin big sagebrush (Artemisia tridentata ssp.

tridentata); mountain big sagebrush (A. t. ssp.

vaseyana); Wyoming big sagebrush (A. t. ssp.

wyomingensis). 2 Means sharing the same superscript are not significantly different at the 95 percent level.
160 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

(see chapter IV for details). So studies were conducted

to measure the amount of variability among accessions and subspecies of big sagebrush grown in uniform gardens for monoterpenoid concentration. The

idea was to locate accessions or subspecies having low

concentrations of monoterpenoids that might be used

in a breeding and selection program to improve the

nutritive value of big sagebrush. Welch and McArthur

(1981) found that the midwinter monoterpenoid (volatile or essential oils) concentration of big sagebrush

was under genetic control, although there is a strong

seasonal factor (Cedarleaf and others 1983). This

conclusion was based on the results of their study,

Table 5.11—Winter crude protein of 13 accessions

of Wyoming big sagebrush (Artemisia

tridentata ssp. wyomingensis). Data

from three uniform gardens were

pooled. Data expressed as the percentage of dry matter. Data from

Welch and others (1992a).

Accessions Percent of crude protein1

Daniel 13.9a

North Kemmerer 13.5ab

Squaw Butte 13.1ab

Arco 13.1ab

Oasis 12.8bc

Rush Valley 12.5bc

Gordon Creek 11.9cd

Warren 11.9cd

Dinosaur 11.9cd

Glenns Ferry 11.8d

Brown’s Park 11.7de

Loa 11.3de

South Fredonia 10.8e

1 Means sharing the same letter superscript are not

significantly different at the 5 percent level.

Table 5.12—Winter total and individual monoterpenoid concentrations of three subspecies of big sagebrush (Artemisia tridentata)

grown in a uniform garden. Data expressed as the percentage of dry matter. Data from Welch and McArthur (1981).

Monoterpenoids1

Subspecies2 a-pinene Camphene 1,8 cineol a-thujone b-thujone d-camphor Terpineol Unknowns Totals

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Percent - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Mountain 0.02a 0.04ab 0.10b 0.27b 0.47b 0.35a 0.19b 0.73 2.20b

Basin .02a .03a .02a .09a .41b .31a .02a .44 1.40a

Wyoming .08b .08b .04ab .04a .01a .58b .01a .19 1.07a

1 Values of total and individual monoterpenoid levels among the subspecies sharing the same superscript are not significantly different at the 5

percent level. 2 Mountain = Artemisia tridentata ssp. vaseyana; basin = A. t. ssp. tridentata; Wyoming = A. t. ssp. wyomingensis.

which showed that mountain big sagebrush contained

significantly higher concentrations of monoterpenoids

than basin and Wyoming big sagebrush growing in a

uniform garden (table 5.12). In addition, certain

accessions of big sagebrush contained significantly

lower concentrations of monoterpenoids than others.

Total monoterpenoids, expressed on a percentage of

dry-matter basis, varied from 0.93 to 2.95 percent

among 20 big sagebrush accessions grown in a uniform

garden (Welch and McArthur 1981) (table 5.13). Welch

and McArthur (1981, p. 380) concluded: “If

monoterpenoids interfere with digestion or have a

negative impact on palatability, breeding and selection schemes can be developed to capitalize on the

significant variation that exists among accessions of

A. tridentata.”

The inheritance of monoterpenoids and other hydrocarbons in big sagebrush has received limited study.

Inheritance of monoterpenoids involving a cross between basin big sagebrush (Dove Creek accession) and

mountain big sagebrush (‘Hobble Creek’ accession) by

McArthur and others (1988) is illustrated in table 5.2.

As explained in an earlier section, the F1 hybrid’s

monoterpenoid profile was, in general, intermediate

between the two parents. These observations have

been extended to F2 hybrids by Weber and others

(1994). They compared the number of volatile compounds detected by capillary gas chromatography from

parental lines with the number of volatile compounds

produced by the F2 hybrids. Capillary gas chromatography detected 25 compounds, some of which were

monoterpenoids, from the Dove Creek parent, 18 from

the ‘Hobble Creek’ parent, and 22, 27, and 37 from the

F2 hybrids. Weber and others (1994) explained that

such results would be expected from the principles of

genetic recombination. In comparing Dove Creek to

‘Hobble Creek’ there were 37 compounds, 19 common

to both, 17 unique to Dove Creek, and one unique to

‘Hobble Creek’. The number of compounds between

Dove Creek and F2 hybrids was 43, 27 common to both,
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 161

County, CO. Schneegas and Nord (1967) described a

monarch big sagebrush plant at 14 feet 8 inches high

in the White Mountains of eastern California. Pase

(1956) found a big sagebrush 15 feet 7 inches tall east

of Kanab, UT. In his checklist of native and naturalized trees of the United States, Little (1953) described

big sagebrush as a small tree that can be as high as 12

to 20 feet, thus earning its namesake among sagebrushes as big sagebrush. In general, basin big sagebrush is the tallest of the three subspecies of big

sagebrush (Beetle 1960, 1962) with Wyoming the

shortest and mountain intermediate (McArthur and

Welch 1982) (table 5.14).

McArthur and Welch (1982) found that the fastest

growing and largest plants were diploid, 2n = 18, and

the slowest and smallest plants were tetraploid, 2n =

36. McArthur and Welch (1982, p. 396) concluded,

“Comparison of three accessions’ performances at two

uniform gardens and their native sites indicated that

growth parameters, while subject to environmental

influences, are under genetic control.” These observations are illustrated in table 5.15. Barker and others

(1983) and Barker and McKell (1983) support the

findings of McArthur and Welch (1982).

eight unique to Dove Creek, and eight unique to F2

hybrids. For the ‘Hobble Creek’ and F2 hybrids comparison, there were 35 compounds, 20 common to both,

none unique to ‘Hobble Creek’, and 15 unique to the F2

hybrids. When they subjected their data set to cluster

analysis, parents and F2 hybrids clustered separately

from one another. Weber and others (1994, p. 696)

concluded with this statement: “Of particular interest

in the current study is the reduced amount of the bitter

methacrolein in some of the F2s. Lowering methacrolein

in hybrid selections while maintaining the desirable

biomass, palatability, and protein values of one or the

other parental species in those hybrid lines gives

promise to the possibility of selection for A. tridentata

for particular rangeland purposes.”

Growth

Mature plant height in big sagebrush is highly

variable. Pool (1908), in an extensive study of big

sagebrush in Colorado, found that big sagebrush plants

ranged in height from 18 inches to 8 feet. A big

sagebrush plant 10 feet tall was reported by Beetle

(1962) in the Wind River Valley of Wyoming and a

plant about 13 feet tall at Dutch Creek in Rio Blanco

Table 5.13—Winter total and individual monoterpenoids concentrations among 20 accessions of big sagebrush (Artemisia

tridentata) grown in an uniform garden. Data expressed as the percentage of dry matter basis. Data from Welch and

McArthur (1981).

Monoterpenoids1

Subspecies2 a-pinene Camphene 1,8 cineol a-thujone b-thujone d-camphor Terpineol Unknowns Totals

Kaibab (w) 0.11d 0.11c 0.02a 0.00a 0.00a 0.63cd 0.01a 0.05 0.93a

Clear Creek (b) .00a .00a .02a .05b .31b .24bc .01a .32 .95a

Milford (w) .05c .03abc .01a .13cd .04a .22bc .00a .33 .99a

Wingate (b) .04c .08bc .01a .02a .02a .71cd .02a .07 1.01a

Big Brush (b) .02bc .08bc .04ab .00a .06a .42bc .02a .38 1.02a

Colton (m) .01b .01ab .01a .02ab .48bc .15b .00a .34 1.02a

Trough Springs (w) .09d .09bc .08bc .00a .00a .89d .02 .24 1.41ab

Dog Valley (b) .02bc .02abc .01a .24d .33b .26bc .03a .60 1.51ab

Pinto Canyon (m) .04c .08bc .06b .04b .01a .54cd .37b .29 1.63ab

Evanston (b) .01b .00a .00a .09bc .89d .13b .01a 0.53 1.66ab

Dove Creek (b) .00a .00a .02a .07bc .71bc .13b .00a .77 1.70bc

Indian Peaks (m) .00a .04abc .12c .03ab .02a .31bc .01a 1.19 1.72bc

Sardine (m) .02bc .11c .06b .25d .58c .62cd .05ab .05 1.74bc

Clear Creek (m) .00a .00a .09c .00a .75cd .00a .18ab .80 1.82bcd

Loa (b) .01b .03abc .09c .13cd .55c .28bc .05ab .76 1.91cd

Alton (m) .04c .07bc .11c .01a .29b .58cd .19ab .69 2.03cd

Petty Bishop (m) .00a .00a .01a .74e .60c .00a .33b 0.88 2.58d

Salina (m) .00a .00a .02a .63c .47bc .00a .31b 1.12 2.60d

Benmore (m) .00a .00a .09c .96f .49bc .05ab .32b .90 2.89d

Durkee Sp. (m) .05c .08bc .41d .00a .85d 1.20d .16ab .12 2.95d

1 Values of total and individual monoterpenoid levels among accessions sharing the same superscript are not significantly different at the 5 percent level. 2 (m) = mountain big sagebrush (Artemisia tridentata ssp. vaseyana); (b) = basin big sagebrush (A. t. ssp. tridentata); (w) = Wyoming big

sagebrush (A. t. ssp. wyomingensis).
162 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Davis and Stevens (1986) also studied the vegetative growth rate of subspecies and accessions within

subspecies grown in uniform gardens. However, their

experimental design differs from the pervious studies

in that they measured growth in terms of grams of dry

matter per centimeter of leader length as compared to

length of vegetative leader or current year’s growth.

They were unable to demonstrate a statistical difference among subspecies, but their data did show a

trend that favored mountain big sagebrush (0.346 g/

cm) over basin (0.303 g/cm) and basin over Wyoming

(0.293 g/cm). When their values (grams of dry matter

per centimeter of leader length) for the three subspecies of big sagebrush are combined or multiplied with

the values for vegetative leader length (table 5.14),

basin big sagebrush was 9.00 g per leader length,

which exceeded mountain at 7.06 g, which in turn

exceeded Wyoming at 5.07 g. Still valid are the observations by previous workers that in general basin big

sagebrush is a larger subspecies than mountain, and

mountain is larger than Wyoming (Barker and McKell

1983; Barker and others 1983; McArthur and Welch

1982; Welch and McArthur 1986a).

The influence of genetics on growth rates among

subspecies and accessions of big sagebrush is illustrated in a greenhouse study conducted by Booth and

others (1990). They were able to grow big sagebrush

plants representing three subspecies that were, in

turn, represented by four or five accessions in a

nonlimiting environment for 25 weeks. Results of this

study are shown in figure 5.5. Three points are apparent: (1) over an extended period and in a nonlimiting

environment, the rate of seedling growth in Wyoming

big sagebrush approached zero and was less than that

of seedlings of basin and mountain big sagebrush; (2)

basin and mountain big sagebrush continued to have

nonnegligible growth rates even at the end of the 25-

week growing period; and (3) Wyoming big sagebrush

reached its point of maximum growth rate approximately 2 weeks earlier than did the other two subspecies. Because this study was conducted in a nonlimiting

environment, they concluded that genetic factors, not

environmental factors, were responsible for limiting

seedling growth of Wyoming big sagebrush. It would

appear that evolutionary pressures, mainly dryness

and shallow soils, resulted in the development of

genetic control for smallness in Wyoming big sagebrush plants. Smallness would allow Wyoming big

sagebrush to survive on xeric sites, where basin and

mountain big sagebrush cannot.

Results of the Booth and others (1990) study disagree with the report of Harniss and McDonough

(1975). They were unable in a 10-week study to differentiate the rate of growth of seedlings among the three

subspecies.

Table 5.14—Subspecies mean annual

vegetative leader lengths

of big sagebrush (Artemisia tridentata) plants

grown for 5 years in three

uniform gardens. Data expressed as centimeters of

current year’s growth. Data

from Welch and McArthur

(1986a).

Subspecies1 Length2

cm

Wyoming 17.3a

Mountain 20.4b

Basin 29.6c

1 Wyoming = Artemisia tridentata ssp.

wyomingensis; mountain = A. t.ssp.vaseyana;

basin = A. t. ssp. tridentata. 2

 Means sharing the same superscript are

not significantly different at the 5 percent level.

Table 5.15—Mean vegetative leader lengths of 21

accessions of big sagebrush (Artemisia tridentata) plants growth on two

uniform gardens for 5 years. Data expressed as centimeters of current year’s

growth. Data from Welch and McArthur

(1986a).

Accession1 Length2

cm

Petty Bishop’s Log (m) 15.3a

Trough Creek (w) 15.5a

Evanston (w) 15.8a

Big Brush Springs (b) 16.7ab

Colton (m) 17.2ab

Milford (w) 17.2ab

Benmore (m) 18.8bc

Clear Creek Canyon (m) 20.1cd

Sardine Canyon (m) 20.2cd

Durkee Springs (m) 20.6cde

Kaibab (w) 20.7cde

Wingate Mesa (b) 20.9cde

Indian Peaks (m) 22.4def

Salina Canyon (m) 23.0ef

Hobble Creek (m) 23.1ef

Pinto Canyon (m) 23.2f

Clear Creek Canyon (b) 30.8g

Evanston (b) 30.9g

Dog Valley (b) 33.0h

Loa (b) 33.1h

Dove Creek (b) 41.4i

1 (m) = mountain big sagebrush (Artemisia tridentata ssp.

vaseyana); (w) = Wyoming big

sagebrush (A. t. ssp. wyomingensis); (b) = basin big sagebrush (A. t. ssp. tridentata). 2 Means sharing the same superscript are not significantly

different at the 5 percent level.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 163

In a companion study to that of Booth and others

(1990), Welch and Jacobson (1988) reported that for

the first 10 days after germination the rate of root

growth of Wyoming big sagebrush significantly exceeded that of basin and mountain big sagebrush. Part

of this faster root growth was attributed to a faster

germination rate for Wyoming big sagebrush. At 20

and 30 days, the rate of root growth of Wyoming and

basin big sagebrush was not significantly different,

but both significantly exceeded mountain big sagebrush. At 40 days, the rate of root growth of basin big

sagebrush significantly exceeded that of Wyoming,

which, in turn, exceeded mountain. At 174 days, basin

(926 mm) and Wyoming (876 mm) big sagebrush root

lengths were significantly longer than mountain (680

mm), but were not different from each other.

Thus, it appears that Wyoming big sagebrush has

evolved to achieve maximum aboveground growth

rate early in the growing season but limits the amount

of aboveground growth. Limiting aboveground growth

would allow the plant to assign energy to rapid root

growth and development, characteristics that are important for surviving a xeric site. There appears to be

exploitable genetic variability among subspecies and

accessions within subspecies for growth that may be

incorporated in a selection and breeding program

aimed at combining rapid growth with other desirable

characteristics. However, rapid growth cannot be supported by all environments that big sagebrush live in.

Germination

There appear to be genetic factors involved in the

expression of germination patterns among subspecies

and accessions within subspecies. Meyer and Monsen

(1992) found that mountain big sagebrush contained a

higher percentage of dormant seeds that germinated

slower than basin and Wyoming big sagebrush seeds.

McDonough and Harniss (1974) noted lower mean

percent germination for mountain big sagebrush as

compared to basin and Wyoming big sagebrush and

that stratification increased seed germination for all

accessions of mountain big sagebrush and for some

accessions of basin and Wyoming big sagebrush. Young

and others (1991) found differences in germination

profiles among accessions of big sagebrush. Meyer and

Monsen (1992, p. 87) were able to relate some of these

germination profile differences to environmental

Figure 5.5—The growth rate of seedlings of three subspecies of big sagebrush

(Artemisia tridentata) in a non-limiting water environment (after Booth and others

1990).
164 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

differences: “Collections from severe winter sites required up to 113 days to germinate to 50% at 1° C,

while collections from mild winter sites required as

few as 6 days.” Details on germination patterns among

big sagebrush subspecies and accessions within subspecies are given in chapter VI.

Summary

An alternate title for this section on variability could

be “Not All Big Sagebrush Are Created Equal.” Due to

the large variability expressed among subspecies and

accessions within subspecies of big sagebrush for preference, digestibility, crude protein, monoterpenoids,

growth or biomass production, and germination, it is

apparent that big sagebrush has a rich, variable

germplasm. A rich, variable germplasm is the foundation on which successful selection and breeding programs are based. In the next section, I will discuss the

feasibility of improving big sagebrush through selection and breeding (Welch and McArthur 1979a).

Selection and Breeding __________

Voigt (1975, p. 42) stated in the Improved Range

Plants Symposium, “Species that are aggressive,

productive, and persistent are the ones most likely to

benefit from increased forage quality and possibly

from increased palatability.” Perhaps few Western

native range plants are more aggressive, productive,

and persistent than big sagebrush. Big sagebrush

contains a rich array of characters (McArthur 1981).

This genetic diversity provides the opportunity for

finding (selection) or building (breeding) superior big

sagebrush germplasms and cultivars that could better meet the needs of land managers (Plummer 1972;

Welch and others 1986b). Success of a big sagebrush

improvement program depends on the degree that

improved big sagebrush germplasms and cultivars

meet specific management needs (Plummer 1972;

Welch 1994). A precise description of management

needs is therefore basic. These needs vary but fall

into three general categories: soil stabilization, animal habitat, and esthetics (Blaisdell 1972). For soil

stabilization, evaluation criteria would include: rooting characteristics such as depth, distribution, and

soil binding ability; potential resistance to disease

and insect problems; ease of establishment such as

direct seeding, site preparation, competitiveness, and

seedling vigor; palatability (for some needs, unpalatable big sagebrush may be desirable); longevity; and

adaptation to the environmental conditions detailed

in the description of management needs. Animal

habitat needs include forage and cover. Forage must

meet the nutritional requirements of target animals

(Welch and McArthur 1990). These requirements are

digestibility, minerals, vitamins, protein, and biomass production (see chapter IV for more details).

Cover requirements of target animals include thermal, escape, nesting, and breeding. Evaluation criteria for cover include not only basic survival characteristics, but also form (height, spread) and

compatibility with other plant species.

The heart of a big sagebrush selection and breeding

program is the performance of subspecies and accessions in uniform gardens. Uniform gardens standardize the environmental effect on character expression,

and any differences are due to genetic differences that

may be exploitable (McArthur and others 1985). Exploitable variability for a host of important characteristics has been discussed in the previous section (tables

5.4 through 5.15).

Selection

A need that has been worked on for some years is to

raise the nutritive level of forage plants on critical big

game winter ranges (Blaisdell 1972). Because of its

superior winter nutritive content (see chapter IV for

details) big sagebrush became the leading candidate

to meet this need. “No matter how abundant or how

nutritious a plant may be, it has no value as fodder

unless animals eat it” (Everist 1972). The search for

palatable forms of big sagebrush that could be used on

big game winter ranges began in the late 1960s with

the establishment of uniform gardens at Gordon Creek

near Helper, UT, and at the Snow Field Station at

Ephraim, UT (Hanks and others 1971; Plummer and

others 1968). This search resulted in the release,

through the Utah Crop Improvement Association, of a

named selection of mountain big sagebrush collected

at the mouth of the Hobble Creek Canyon east of

Springville, UT, named ‘Hobble Creek’ (Welch and

others 1986a).

‘Hobble Creek’ Mountain Big Sagebrush

‘Hobble Creek’ mountain big sagebrush was released for use on mule deer and domestic sheep winter

ranges, sage grouse habitat, and restoration projects

(McArthur 1988; Welch 1992, 1993; Welch and others

1986a). Of the 186 big sagebrush accessions tested in

Utah, ‘Hobble Creek’ was the most preferred by wintering mule deer (Welch and others 1986a) (table 5.5).

In studies conducted in Colorado, Idaho, Oregon, and

Washington, winter mule deer preferred ‘Hobble Creek’

over native big sagebrush (Welch 1993; Welch and

others 1986a, 1992b). It was also preferred by winter

mule deer over an unknown selection of antelope

bitterbrush (Purshia tridentata) (Welch and Wagstaff

1992). Wintering domestic sheep, on the other hand,

ranked ‘Hobble Creek’ high but not as most preferred

(Welch and others 1987) (table 5.6). Similar results
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 165

were obtained for sage grouse (Welch and others

1991). In Utah and Oregon, pronghorn antelope ate a

high percent of the current year’s growth of ‘Hobble

Creek’ plants (Welch and others 1992b).

Winter crude protein content of ‘Hobble Creek’ big

sagebrush is 11 percent of dry matter, which is well

above the maintenance requirement of 7 to 8.9 percent. This ranks high among winter forages, in general, but as a big sagebrush its winter crude protein

level is below the average of those tested in table 5.9.

Winter phosphorus content of ‘Hobble Creek’ is 0.21

percent of dry matter, which, like crude protein, ranks

high for a winter forage but somewhat average for a

big sagebrush. Winter in vitro digestibility of ‘Hobble

Creeks’ dry matter is 52.6 percent, just below the

average of big sagebrush accessions tested in table 5.7.

‘Hobble Creek’ big sagebrush productivity, expressed

as length of vegetative leader growth, was exceeded

only by five accessions of basin big sagebrush tested

(table 5.14). ‘Hobble Creek’ productivity, expressed as

grams per centimeter of vegetative stem, ranked third

out of 20 accessions tested (Davis and Stevens 1986).

‘Hobble Creek’ big sagebrush can be grown or

established on sites with the following physical

characteristics:

1. Mean annual precipitation of 14 or more inches.

2. Deep, well-drained soils with an effective rooting

depth of at least 4 feet.

3. Soil no finer than clay loam (40 percent clay or

less). On sites with heavy clay soils, ‘Hobble Creek’

appears to be predisposed to root rot and vascular wilt

type pathogens.

4. Soil pH between 6.6 and 8.6.

5. Growing season of 90 days or more.

Because of shallow soils and lower precipitation, trying to establish Hobble Creek on Wyoming big sagebrush sites is not recommended.

‘Hobble Creek’, like other types of big sagebrush, can

be established on suitable sites by direct seeding onto

properly prepared seedbeds and by transplanting

bareroot or containerized stock (see chapter VI for

details).

Gordon Creek Wyoming Big Sagebrush

For dryer habitats, 10 to 13 inches of precipitation

per year, uniform gardens of Wyoming big sagebrush

were established on three mule deer winter ranges in

Springville, UT, Glenns Ferry, ID, and Taylor Flats in

Brown’s Park, UT, about 12 mile east of Dutch John

(Welch and others 1992a). Thirteen accessions were

collected from geographically distinct sites in the States

of Utah, Idaho, Arizona, Oregon, Colorado, Montana,

and Wyoming (Welch and others 1992a). Each accession was evaluated in terms of current year’s growth of

vegetative leaders, winter mule deer preference, winter crude protein, phosphorus content, and in vitro

digestibility.

Based mainly on the preference measurements, an

accession of Wyoming big sagebrush collected from the

Gordon Creek area near Helper, UT, was chosen as a

superior tested germplasm of Wyoming big sagebrush

(Welch and others 1992a). While not as preferred as

‘Hobble Creek’ big sagebrush, wintering mule deer

utilized a significantly higher percentage of its current

year’s vegetative growth as compared to the remaining Wyoming big sagebrushes (Welch and others

1992a). Sage grouse also will eat it (Welch and others

1991). Its nutritive value ranked in the middle of the

accessions tested for crude protein at 11.9 percent of

dry matter, in vitro digestibility at 52.8 percent, and

phosphorus at 0.21 percent (tables 5.8 and 5.11) (Welch

and others 1992a). While these nutritive values exceed most winter forages, as a big sagebrush, they are

about average (Welch 1989).

Gordon Creek Wyoming big sagebrush germplasm

appears to be widely adapted and can be grown on sites

with the following physical characteristics:

1. Mean annual precipitation of 10 to 13 inches.

2. Deep to shallow, well-drained soils.

3. Clay content to 55 percent.

4. Soil pH between 6.6 and 8.8.

5. Growing season of at least 80 days.

Breeding

Pendleton and others (1989) described the breeding

system of big sagebrush as wind-pollinated, perfect

flower producing a dry fruit called an achene that is 2

to 3 mm in diameter (also see McArthur 1984, 1989).

McArthur (1984) observed that self-pollination is possible, but outcrossing leads to a higher production of

viable achenes or seeds and greater population variability. Pendleton and others (1989) classified the

dispersal of big sagebrush achene as microwind, meaning that the achenes are dispersed by wind because

they are light and small but lack any special structures that would enhance floating or moving with the

wind.

Not all superior characteristics are expressed in a

single accession or subspecies of big sagebrush (see

tables 5.5 through 5.15). For example, ‘Hobble Creek’,

an accession of mountain big sagebrush, is most preferred by wintering mule deer, but Dove Creek, an

accession of basin big sagebrush, is more digestible,

contains higher amounts of crude protein, and produces greater vegetative leader growth or biomass. In

addition, both ‘Hobble Creek’ and Dove Creek are

diploids and have compatible chromosome numbers

(McArthur and others 1981; McArthur and Sanderson

1999). Therefore, a superior form of big sagebrush
166 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

could be achieved if the nutritive characteristics of

Dove Creek could be combined with the high preference of ‘Hobble Creek’.

Hybridization between ‘Hobble Creek’ and Dove

Creek has been described in a previous section. Resultant hybrids are for the most part intermediates of the

two parental lines. However, hybrid growth performance is subject to environmental x genotype interaction; F2 plants grew at intermediate rates (fig. 5.6;

McArthur, unpublished data) at the Upper Colorado

Environmental Plant Center at Meeker, CO, but

demonstrated equal growth rates to parental plants

at Green Canyon, near Logan, UT (Messin and

others 2002). Unfortunately, hybrids have not been

evaluated either for nutritive characteristics or for

their environmental adaptation. Leaf shape of the

hybrid is broadly cuneate, like that of the paternal

line—‘Hobble Creek’ (fig. 5.6).

An accession of Wyoming big sagebrush, a tetraploid, has been successfully hybridized with silver sagebrush (Artemisia cana; McArthur and others 1998b;

McArthur and Sanderson 1999). The idea behind this

cross is to combine the widespread adaptability of

Wyoming big sagebrush with the root-sprouting firetolerance ability of silver sagebrush as a means of

maintaining woody species on areas exposed to frequent fires due to the presence of cheatgrass (Bromus

tectorum) and other alien annual weeds.

Figure 5.6—Maternal (Dove Creek—basin big sagebrush—Artemisia tridentata ssp. tridentata–large

photo left) and paternal(‘Hobble Creek’—mountain big sagebrush—A. t. ssp. vaseyana–bottom right

photo) used to produce F2 hybrid (top right photo). All three plants are shown growing in a uniform garden

(photos by E. Durant McArthur).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 167

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Temperature profiles for germination of big sagebrush seeds from

native stands. Journal of Range Management. 44: 385–390.
170 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Notes

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Chapter

VI

Putting Big Sagebrush

Back Into Its Ecosystem

This chapter covers the principles of establishing big sagebrush stands in areas where

they have been destroyed; the production, harvesting, cleaning, and storage of big

sagebrush seeds; and seed dispersal.

Establishment ____________________________________________________

Big sagebrush can be established on suitable sites by direct seeding, by transplanting

bareroot or containerized stock, or by a technique termed “mother plant.” Descriptions

of these techniques follow (McArthur and others 1974; Plummer and others 1968; Welch

and others 1986, 1992).

Direct Seeding

Direct seeding is the most practical method of establishing big sagebrush on areas

larger than 10 acres. The first step in establishing a big sagebrush stand is obtaining

high-quality, certified (source-identified and pathogen-free) seed. Chapter I noted that

the three major subspecies of big sagebrush discussed in this work grow on vastly

different sites or habitats. Wyoming big sagebrush occupies the driest and hottest big

sagebrush habitats, whereas mountain big sagebrush occupies the wettest and coolest

habitats, with basin somewhat intermediate between the two. Therefore, the first job

in any attempt to reestablish big sagebrush is to determine what subspecies of big

sagebrush the prospective site supported. Mountain big sagebrush will do poorly on the

dry and hot Wyoming big sagebrush sites and, conversely, Wyoming big sagebrush will

do poorly on mountain big sagebrush sites.

Selection of Seed Source

Several studies show that seeds of the different big sagebrush subspecies germinate

differently. McDonough and Harniss (1974a), studying the germination rate of seed

collected from the three subspecies of big sagebrush, noted that basin big sagebrush

germination percentages were significantly higher than those of Wyoming and mountain big sagebrush, and Wyoming was significantly higher than mountain big sagebrush

under the conditions of their experiment. Evans and Young (1986) studying germination

profiles for five populations of big sagebrush reported higher germination percentages
172 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

for seeds of basinbig sagebrush compared to mountain

big sagebrush (also see Young and others 1991). Unfortunately, there was no indication that ungerminated

seeds were checked for viability; thus, the differences

noted among subspecies may be due to the presence of

dormant seeds that may require additional treatments to break dormancy. In fact, stratification of

mountain big sagebrush seeds for 30 days increased

their germination percentage well above those of basin and Wyoming big sagebrush (McDonough and

Harniss 1974a). McDonough and Harniss (1974b),

characterizing seed dormancy of mountain big sagebrush, found that removal of pericarp from achenes

stimulated germination to 95 percent; in addition, the

germination rate, that is the number of days to reach

one-half of final percentage germination, was reduced

to 1 day as compared to 8 to 12 days for other treatments. McDonough and Harniss (1974, p. 19) concluded: “Under natural conditions, the combined effects of winter stratification on the promotion of

growth of the embryo and erosion of the pericarp by

weathering and by the action of soil micro-organisms

probably insure prompt and nearly complete germination by the time of snowmelt in spring.” The point

is that mountain, basin, and Wyoming big sagebrush

all evolved under different environmental conditions

and do not grow well or compete well in the others’

environment.

Meyer conducted several experiments in the early

1990s (Meyer 1990; Meyer and Monsen 1990, 1991,

1992; Meyer and others 1990) that compared the

germination rate of big sagebrush subspecies and

sources or populations within subspecies from sites

varying in winter severity. She defined germination

rate as the number of days to reach 50 percent of final

germination and severity of winter as the mean January temperature. Her results showed a strong negative relationship between mean January temperature

and germination rate and percent of dormant seeds.

That is, the warmer the mean January temperature,

the fewer days needed to reach 50 percent of final

germination, and a smaller percent of the seeds were

dormant. Those subspecies and sources or populations

within subspecies from the severest winter sites required the greatest number of days to reach 50 percent

germination at 1 °C and, in the case of mountain big

sagebrush, exhibited the greatest percentage of dormant seeds. These relationships for mountain big

sagebrush are illustrated in table 6.1. For all subspecies and sources or populations of big sagebrush studied, the number of days to 50 percent varied from 16 to

113. She also noted that basin and Wyoming big

sagebrush seeds were essentially nondormant compared to mountain big sagebrush.

Allen and Meyer (1998, p. 183) explained the significance of Meyer’s work:

Population from severe winter sites, where the major

risk to seedlings is frost, tend to have long chilling

requirements or to germinate very slowly at low temperatures. Populations from warmer sites, where the

major risk is drought, are non-dormant and germinate

very rapidly under these same conditions. Seed populations from intermediate sites exhibit variation in dormancy levels, both among and within plants, which

spreads germination across a considerable time period.

Therefore, it is important to determine not only

what subspecies of big sagebrush a prospective rehabilitation site supported or would support but also

whether the site represents a severe, intermediate, or

warmer winter site and to obtain big sagebrush seed

that match these criteria (Meyer and Monsen 1993).

Because the inflorescences of big sagebrush are

indeterminate, achene or seed quality varies with

temperature, moisture, and time; therefore, all seedlots

must be checked for viability of achenes or seeds (see

plate V, fig. 75, of chapter I). Achenes harvested too

early will not be filled and will show signs of shrinkage. Proper cleaning should remove most, if not all, of

these shriveled nonviable achenes. Bai and others

(1996) found that heavier Wyoming big sagebrush

seeds exhibited higher germination and germination

rates (also see Senft 1996). Viability tests by tetrazolium chloride (Weber and Wiesner 1980) should be at

least 80 percent. Once an adapted and viable seed

source has been collected or selected, the next task in

restoring big sagebrush is seedbed preparation.

Seedbed Preparation

Seedbed preparation has two basic goals: firming

the soil and reducing competing vegetation (Blaisdell

1949; Meyer 1994; Plummer and others 1968; Shaw

and Monsen 1990). Because of the small size of big

sagebrush seeds and limited energy reserves, seeds

must germinate near or on the surface of the soil

(Jacobson and Welch 1987). If big sagebrush seeds are

planted or buried too deep in the soil, they could run

out of energy before emergence. In the case of populations requiring light for germination, buried seed may

not receive the necessary quantity of light needed for

germination (McDonough and Harniss 1974b; Meyer

and others 1990; Shaw and Monsen 1990; Weldon and

others 1959). However, Meyer and others (1990) showed

that the light requirement is almost completely relieved with stratification for 2 weeks at 1 °C. Shaw

and Monsen (1990) suggested delaying planting in

fall/winter until after a rainstorm, which firms soil

surfaces. The use of a cultipacker or land-imprinting

implement can also help to firm loose soil surfaces and

prevent soil sloughing and burying big sagebrush

seeds too deep.

Young and Martens (1991) noted that big sagebrush

seeds germinating on the surface of the seedbed must

satisfy two important conditions: first, uptake of
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 173

moisture from the soil surface must be faster than it is

lost to the atmosphere, and second, seedling radicle

must grow into the soil and begin absorbing water as

soon as possible. Young and Martens (1991, p. 438)

also observed that “achenes of big sagebrush are not

truly mucilaginous, but the achene coat becomes gelatinous when imbibed, which may aid moisture relations.” During a microphotographic study of big sagebrush radicles and hypocotyls emergence, Young and

Martens (1991) observed the development and rapid

growth of hypocotyl hairs during the early phases of

germination. These hairs form a dense ring around the

lower region of the hypocotyl and the radicle emerges

through this ring. They believe that the hairs attach

the germinating seedling to the surface of the soil, thus

aiding the radicle to penetrate into the soil. Mucilagelike substance was found among the hairs, which

probably help cement the hairs to soil particles. Young

and Martens (1991, p. 438) further observed: “In most

studies, dislodging the seedling and breaking the

contact of the hypocotyl hairs to the substrate reduced seedling survival and increased the number of

surviving seedlings with abnormal geotropism.”

Chambers (2000) noted that seeds lacking appendages

and with small surface areas, such as big sagebrush,

do not experience significant horizontal movement.

Thus, it appears that big sagebrush has evolved certain germination processes that allow it to cope with

the rigors of a surface environment.

Competition can be reduced by using three basic

methods: fire, herbicide, or mechanical cultivation

(Boltz 1994; Fisser 1981; Plummer and others 1968).

Fires are the least costly and are effective in reducing

competition, but fires are nondiscriminating; that is,

tree, shrub, and forb species are all killed or thinned,

and highly intense fires can remove needed litter,

reduce water infiltration, increase erosion, decrease

available moisture, and create an unstable seedbed

(Monsen and McArthur 1985). Herbicides, on the

other hand, are expensive but effective and can be

selected to kill all types of vegetation or certain segments such as dicots (woody and other broadleaf

plants) or monocots (grasses) without the negative

effects of high-intensity fires. Mechanical cultivation

Table 6.1—Comparison of 24 mountain big sagebrush (Artemisia tridentata ssp. vaseyana)

populations as to severity of winter (as defined by mean January temperature)

percent of dormant seed, and germination rate at 1 °C (defined by number of days to

50 percent of final germination) (after Meyer and Monsen 1992).

Mean Percent dormant Germination

Location State January temperature seed rate

°C Days

Kemmerer WY –8.9 45 107

Nebo Overlook UT –8.9 30 103

Huntsville UT –8.3 13 90

Scow’s Hollow UT –8.3 58 112

Daniel WY –8.3 27 113

Reynolds Creek ID –7.8 58 108

Maple Canyon UT –7.8 60 110

Mirror Lake Road UT –6.7 36 100

Park City UT –6.1 31 98

Thorn Creek Junction ID –6.1 1 50

Hailstone Junction UT –5.6 9 88

Squaw Butte OR –4.4 3 54

Lucky Peak ID –3.9 8 54

Wheeler Guard Station CA –3.3 0 60

Lee Vining CA –3.3 3 41

Hiko NV –2.8 0 26

Pine Valley UT –2.2 0 52

Bootleg Campground CA –2.2 0 40

Nephi UT –1.7 0 45

Gardinerville NV –1.1 0 34

Browse Offramp UT –0.2 0 44

Upper Kyle Canyon NV 1.1 0 32

Lower Kyle Canyon NV 2.6 0 16

Utah Hill UT 2.8 0 30
174 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

is also expensive but can be a selective or broad

spectrum in the killing or thinning of competitive

vegetation (see chapter VII for more details concerning fire, herbicides, and mechanical cultivation) (Boltz

1994; Plummer and others 1968).

Planting

After seedbed preparation, the next step is planting.

The best time to plant big sagebrush seed is in the late

fall (late November early December), about the same

time that the seeds are naturally dispersing

(Deitschman 1974; Ferguson and Frischknecht 1981;

Fisser 1981; Meyer and Monsen 1990; Rosentreter

and Jorgensen 1986; Shaw and Monsen 1990; Stidham

and others 1980; Van Epps and McKell 1977; Vories

1981; Welch and others 1986, 1992; Young and Evans

1986). Klott and Ketchum (1991) demonstrated that

big sagebrush can be seeded successfully on a burned

site by broadcasting the seeds onto snow that is 4 to 8

inches deep. Payne (1957) found that big sagebrush

seeds sown in greenhouse flats in January and placed

out of doors under snow cover germinated 2 days after

snowmelt (April 12), and he concluded (p. 42): “This

early germination was considerably ahead of the germination of other plants which may be a factor accounting for the dominance of big sagebrush in certain

areas.” Planting after February is extremely risky,

particularly on the drier Wyoming big sagebrush sites

and for ecotypes of mountain big sagebrush that require long stratification periods.

Jacobson and Welch (1987) conducted a greenhouse

study to determine the optimal planting depth for big

sagebrush seeds. Their results showed that the optimal planting depth is 0.2 inch or less (table 6.2). These

results are in general agreement with the recommendations of other workers (Deitschman 1974; Fisser

1981; Kelsey 1986; Meyer 1994; Rosentreter and

Jorgensen 1986; Shaw and Monsen 1990; Vories 1981).

Apparently, frost heaving or expansion and contraction of the soil surface due to wetting and drying is

enough to cover surface-sown big sagebrush seeds

sufficiently for germination and establishment. Young

and others (1990) found that big sagebrush seeds

placed on the soil surface may be buried by a process

called winnowing.

Big sagebrush seeds can be planted with any planter

that will deposit the seeds on the surface of a firm

seedbed. These include aerial seeders, cyclone seeders, dribblers, and drills that have been adjusted to

drop the seeds into furrows onto the soil surface

without covering them (Welch and others 1986, 1992).

When using a drill to plant big sagebrush with other

species, Richardson and others (1986) and Rosentreter

and Jorgensen (1986) recommend that the big sagebrush seeds be placed in separate compartments of the

drill, and these compartments adjusted to place the

seeds on the surface of the seedbed. This lessens

intrarow competition between big sagebrush seedlings and seedlings of other species. To prevent clogging of the drill tube, much of the trash usually

associated with big sagebrush seed will need to be

removed. Preparation or planting methods that create

a loose, sloughing seedbed must be avoided. Thus,

under certain situations the use of drills must be

avoided (Meyer 1994).

The amount of big sagebrush seed to plant on a peracre basis has not been well studied. Recommendations vary from 0.065 to 1.33 pounds of pure live seed

per acre (Boltz 1994; Cotts and others 1991; Plummer

and others 1968; Meyer 1994; Quinney and others

1996; Richardson and others 1986; Rosentreter and

Jorgensen 1986; Shaw and Monsen 1990; Skousen and

others 1989; Welch and others 1986, 1992). Richardson

and others (1986) measured the influence of varying

seeding rates of grasses-forbs, shrubs, and mountain

big sagebrush, and the effects of grazing on the establishment of mountain big sagebrush on mine disturbances. The results of their research are given, in part,

in table 6.3. Protected plots yielded a greater number

of mountain big sagebrush plants, and treatments

containing zero amounts of grass and forb seeds also

resulted in the greatest number of mountain big sagebrush plants. A seeding rate of 14.96 pounds per acre

of pure live seed (pls) of grass and forbs, with 5.95

pounds pls of shrubs of which 0.42 pounds pls was

mountain big sagebrush, yield one mountain big sagebrush plant for about each 10 feet2

. These workers

used a Brillion grass-seeder to plant the various mixtures (also see Richardson and Trussell 1981). This

seeder has two sets of cultipacker type rollers, and the

seeds are metered out between the front and rear sets

of rollers, which firms the seedbed but probably buries

Table 6.2—Optimal planting depth for mountain big sagebrush

(Artemisia tridentata ssp. vaseyana) stratified and

unstratified seeds. Data are expressed as a mean

and standard deviation per depth for five pots

containing 15 seeds per pot (after Jacobson and

Welch 1987).

Seed treatment

Stratified Unstratified

Depth seeds germinated1 seeds germinated1

Surface 9.6 ± 1.02a 7.0 ± 0.89a

0.07 inch 9.8 ± 0.81a 5.4 ± 3.01a

0.2 inch 9.0 ± 0.89a 6.6 ± 1.10a

0.4 inch 0.0 ± 0.00b 1.8 ± 1.17b

0.6 inch 0.0 ± 0.00b 0.4 ± 0.80b

1 Means sharing the same superscript within a seed treatment are not

significantly different at the 5 percent level.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 175

some of the mountain big sagebrush too deep. Therefore, a greater quantity of seeds may be required to

achieve the same number or density of plants compared to a broadcast type of planter, which would not

create a firm seedbed, so establishment could be lower

and seed requirement greater.

Vicklund and others (2004) studied the influence of

grass seeding rates on Wyoming big sagebrush plant

density on mine spoils. They (Vicklund and others

2004, p. 42) noted: “Sagebrush seedling density after

three growing seasons was not significantly different

among grass seeding rates..., although, sagebrush

seedling density within the 14 kg PLS per ha [12.474 lbs

per acre] grass seeding rate was less than half that

observed at the lower grass seeding rates.” Grass

seeding rates above 4 kg PLS/ha (3.564 lbs PLS/a) did

have a significant negative impact on canopy volume

of Wyoming sagebrush seedlings. On completion of

their study, Vicklund and others (2004), recommended

the following seeding rate: 2 kg PLS per ha (1.782 lb/

acre) of Wyoming big sagebrush and 4 kg PLS per ha

(3.564 lb/acre) of grasses.

Interseeding

Van Epps and McKell (1977) have established big

sagebrush by direct seeding in stands of native and

introduced perennial grasses by a technique known as

interseeding (also Shaw and Monsen 1990; Stevens

1994). The steps are basically the same as those

outlined earlier in the planting section, except the

whole area or plant community is not altered; only

strips or spots are treated with herbicides or by mechanical means such as pitters, scalpers, rototillers, or

plows to reduce competition and firm the seedbed

(Pendery and Provenza 1987; Shaw and Monsen 1990).

Van Epps and McKell (1977) noted that scalps should

be at least 24 inches wide for native perennial grasses

and greater (40 inches) for the more aggressive grass

species such as crested wheatgrass (Agropyron

cristatum).

Owens and Norton (1992) studied the survival of

basin big sagebrush seedlings in ungrazed pastures

and in pastures with protected and unprotected seedlings that were spring grazed by cattle and sheep.

They found that unprotected seedlings in grazed pastures suffered the greatest mortality due mainly to the

trampling effects of the grazing animals. Owens and

Norton (1990) reported that small (less than 50 cm2

crown area) juvenile basin big sagebrush plants suffered the greatest mortality due to livestock grazing.

Larger plants suffered much less. However, Austin

and Urness (1995) found that horse grazing in spring

benefited big sagebrush seedling survival and seedling recruitment. All three of these studies were conducted on sites having mature big sagebrush plants

already present; protection of newly seeded sites of

big sagebrush for 2 to 3 years seems the prudent

thing to do.

Transplanting Bareroot and Containerized

Stock

Because of the expense, the usefulness of transplanting bareroot or containerized stock is limited to

small, critical areas such as seed-increase gardens,

demonstration plots, and roadsides (Everett 1980;

Shaw 1981; Shaw and Monsen 1990). The same principles of source selection (subspecies and types of

winters) must be adhered to as outlined in the direct

seeding section. Planting stock should be from 4 to 8

inches tall with a well-developed root system that

completely binds the growing medium together, and

overwintered in a nonheated nursery bed or lathhouse

Table 6.3—Number of established mountain big sagebrush (Artemisia tridentata

ssp. vaseyana) plants per acre per seeding rate treatment and for

grazed and protected sites (after Richardson and others 1986). Seeding

rate treatments are expressed as pounds of pure live seeds planted per

acre.

Seeding rate Mountain big sagebrush plants

Grass-forb Shrub Big sagebrush Grazed Protected

9.87 1.18 0.08 54 81

14.96 1.18 .08 37 0

41.62 1.18 .08 46 0

14.96 5.95 .42 3,538 4,530

.00 1.18 .08 no data 2,207

.00 13.41 .95 1,742 7,663

.00 14.91 1.06 2,439 5,343
176 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

(Ferguson and Frischknecht 1981). Methods outlined

by Nelson (1984) should be followed to produce disease-free stock. Actual transplanting of properly hardened planting stock can occur as soon as the frost has

left the soil and the soil is tillable (Ferguson and

Frischknecht 1981). Early spring transplanting of

properly hardened (this takes 3 to 6 weeks) planting

stock is highly recommended (Shaw 1981; Shaw and

Monsen 1990). Advantages of early spring planting

include: (1) maximum soil moisture, (2) minimal frost

heaving, (3) transplants still dormant, (4) temperatures low, and (5) high probability of spring storms

(Stevens 1994). However, summer transplanting of

containerized stock can be successful if the transplants receive adequate irrigation during the first

growing season. Fall planting of bareroot or containerized stock is not recommended because of the

danger of frost heaving and the lack of dependable soil

moisture. Nonhardened, containerized planting stock,

such as containerized stock grown in greenhouses

during the winter, needs to receive a couple of water

stress treatments before being planted out (Welch and

others 1986).

For each transplant, an area of 0.5 to 1 foot2 needs to

be cleared, one time only, of all grass, forb, and shrub

competition (Pendery and Provenza 1987). The key to

proper competition reduction is the mixing of the soil

and the killing of tops, roots, stolons, and rhizomes.

This can be done with hand shovels, posthole diggers,

or similar tools. Holes must be at the proper depth to

allow the roots to be straight, and the root collar placed

at ground level except for containerized stock (Stevens

1994). The growing medium of containerized stock

should be covered by 0.5 inch of native soil to prevent

wicking of moisture into the atmosphere by the growing medium and thus drying out the transplant (Shaw

and Monsen 1990; Welch and others 1986). Soil must

be packed firmly around the transplant to eliminate

air pockets (Stevens 1994). To enhance survival, a

basin about 0.5 foot in diameter with the transplant at

the bottom, 1 to 3 inches deep, could be constructed

(Ferguson and Frischknecht 1981). The basin would

serve as a water catchment or be filled with water

during dry periods. Shaw and Monsen (1990) suggest

the use of mulching material, furrowing, snow harvesting, and other water harvesting techniques as a

means of enhancing seedling survival (also see Senft

1996). Using polyacrylamide as a soil amendment was

found to be ineffective in aiding the establishment,

growth, or seed production of big sagebrush transplants (Al-Rowaily and West 1994).

Care must be exercised during the planting process

to avoid excessive drying of exposed roots of both

bareroot and containerized stock (Stevens 1994). Roots

need to be kept damp and cool at all times. Stevens

(1994, p. 303) emphasized that “mishandling most

commonly occurs just before placing the transplant in

the soil. Transplants must be moved rapidly from the

protected holding area into the soil to minimize root

exposure.”

When using scalper equipment to reduce competition, Stevens (1994) makes two recommendations:

first, scalping should be perpendicular to direction of

prevailing winter storms (this will harvest snow along

the scalp), and second, scalping depth should be deep

enough to reduce competition but not so deep as to

remove the most fertile portion of the soil. Stevens

(1994) further noted that a tractor-mounted reinforced tree planter works well in combination with a

scalper to plant both bareroot and containerized stock

of big sagebrush. Ferguson and Frischknecht (1981)

suggest that the scalp should be at least 36 inches wide

(also see Van Epps and McKell 1977). Where possible,

the transplants should be protected from heavy grazing for two or three growing seasons (Austin and

others 1994; Shaw and Monsen 1990; Stevens 1994;

Welch and others 1986). Pendery and Provenza (1987,

p. 514) suggest, however, that “it is probably more

important to reduce interspecific competition than to

modify grazing practices when planting shrubs in a

crested wheatgrass stand.” First-year survival rates

should be about 80 percent or higher, assuming normal precipitation (Evans and Young 1990; Shaw and

Monsen 1990; Welch and others 1986).

A cautionary note: Welch (1997) compared the seed

production of big sagebrush plants established from

containerized seedlings to plants established by direct

seeding. He found that seed-derived plants produced

more seeds, larger top growth, deeper roots, lateral

roots nearer the soil surface, heavier root systems, and

a lower death rate than containerized-derived plants.

Therefore, bareroot or containerized-derived big sagebrush plants may not perform as well as seed-derived

big sagebrush plants.

Areas heavily infested (688 plants per square meter)

(Young and others 1976) with exotic annual grasses

such as cheatgrass (Bromus tectorum) will limit, if not

outright eliminate, natural recruitment of big sagebrush; or in other words, these areas have crossed over

thresholds that resulted in the domination of cheatgrass

and will not allow the natural recovery of big sagebrush without human intervention (Young and

Longland 1996). Young and Evans (1989) found in

their study, occurring over 4 years and five sites, that

emerged seedlings of big sagebrush failed to establish

themselves on cheatgrass-dominated sites. Wagstaff

and Welch (1990) also reported failure of big sagebrush recruitment on mule deer winter ranges whose

understory was dominated by cheatgrass and where

mature big sagebrush plants were heavily browsed by

deer.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 177

Heavy browsing on big sagebrush plants will reduce

the number of seed stocks (Rodriguez and Welch

1989). Wagstaff and Welch (1991) found that recruitment could occur if the competition from cheatgrass

was reduced around remnant maternal plants by

tillage after the fall greenup of cheatgrass. Recruitment could also be enhanced by protecting mature

plants from heavy mule deer browsing (see table 6.4

for details). This experiment shows that big sagebrush

can be established on sites dominated by cheatgrass,

as on any other site, when competition has been

reduced per instructions outlined in previous sections.

However, the catch is in maintaining the stand once

establishment has been achieved. Cheatgrass domination is quickly reestablished, along with its frequent

fire cycle, far too frequently for big sagebrush stand

maintenance (Whisenant 1990).

For big sagebrush stand maintenance, cheatgrass

cover must be reduced to the point where it cannot

carry fire. This will undoubtedly require repeated

treatments, starting with burning infested sites before seed dispersal (table 6.5). Even then, some of the

seeds or caryopses survive (table 6.6) and if left unchecked can eventually dominate the site again (Hassan

and West 1986; Monsen and McArthur 1985; Young

and others 1976). Surviving cheatgrass caryopses

can be eliminated through deep burial where soil

conditions would permit the use of a plow or other

tillage equipment such as a disk-chain (Boltz 1994)

that would bury the caryopses at least 1 inch deep.

Repeated burning with a propane field flamer may

further reduce the number of surviving cheatgrass

caryopses (Boltz 1994). An alternative or additional

method would be to allow surviving caryopses to germinate and then use a grass herbicide to kill the

seedlings, keeping in mind that the herbicide would

also kill other grass species but leave woody species

and broadleaf forbs unaffected. A sequence of events

Table 6.4—Number of mountain big sagebrush (Artemisia tridentata ssp. vaseyana) seedlings

counted around mature plants. Treatments were no tillage, early fall tillage before

cheatgrass greenup (Bromus tectorum), and late tillage after cheatgrass greenup

(after Wagstaff and Welch 1990).

Sites

Treatment Pleasant Grove Hobble Creek Diamond Fork Total

No tillage

Number of mature plants 32 34 18 84

Seedlings 0 0 0 0

Early tillage

Number of mature plants — 40 18 58

Seedlings — 0 0 0

Late tillage

Number of mature plants 64 28 — 92

Seedlings 164 557 — 721

Table 6.5—Number of cheatgrass (Bromus tectorum) seedlings per square meter from burned and unburned

big sagebrush communities (after Young and others 1976).

Seedling density

Site Burned Unburned Percent reduction

7 560 5,400 90

8 320 4,800 93

9 46 3,300 99

10 1,100 6,400 86

11 860 5,100 83

12 470 8,600 94
178 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Figure 6.1—A mother plant—white tag—of mountain big sagebrush (Artemisia tridentata ssp.

vaseyana) surrounded by her offspring after protection from excessive browsing by wintering mule deer.

Grass competition—mainly cheatgrass (Bromus

tectorum)—was reduced through tillage after fall

green-up. Photograph taken 3 years after treatment

(photo by Bruce L. Welch).

Table 6.6—Survival of cheatgrass (Bromus tectorum) caryopsis after a burn. Data

expressed as means and standard deviations of caryopsis per square foot

(after Monsen and McArthur 1985).

Treatments Date of burn Number of caryopsis

Highway 6 Juab County, UT June 1984

Burned 1,131 ± 713

Unburned 2,669 ± 2,124

Desert Mountain, Juab County, UT July 1984

Burned 502 ± 366

Unburned 2,746 ± 1,976

Yuba Lake, Juab County, UT August 1984

Burned 186 ± 179

Unburned 2,895 ± 2,433

for cheatgrass control could be: (1) fire, (2) seedbed

preparation, (3) fall planting of broadleaf forbs and

shrubs, (4) spring treatment with grass herbicide,

(5) repeat step 4 when needed, (6) fall planting of

native perennial grass species, and (7) the use of

specific biological control agents, such as head smut,

when available (Meyer and others 1999).

Mother Plant Technique

Plummer and others (1968, p. 85) observed: “Since

wildlings and seedlings are transplanted easily, big

sagebrush can be used widely for stabilizing gullies

and eroding spots on hillsides. Such transplants reproduce and spread easily from seed within a 3- to 7-

year period.” Thus, the mother plant technique is a

combination of transplanting and natural seed dispersal (Shumar and Anderson 1987; Wagstaff and

Welch 1990; Welch and others 1986). This technique

could be used after a fire or some other process that has

destroyed native sagebrush stands. “Mother plants”

are planted as containerized, bareroot, or wildlings on

a grid (50 by 50 feet or greater) or established by handbroadcasting seed to produce “source islands” throughout a site (Quinney and others 1996). The direction of

spread from the mother plants would be dependent on

prevailing fall and winter winds (Wambolt and others

1989). Energy is then directed toward the establishment, maintenance, growth, and protection of the

mother plants on an individual plant basis. This may

include fertilization, irrigation, fencing, and so forth.

Once the mother plants are producing seeds, mechanical or chemical means, if needed, can be used to reduce

competition either in strips or spots as an aid in stand

thickening.

Wagstaff and Welch (1990) described success in

using the mother plant technique to rejuvenate mountain big sagebrush stands on mule deer winter ranges

heavily infested with cheatgrass by using onsite plants

as a seed source. The onsite plants were protected from

heavy browsing and by controlling cheatgrass around

the mother plants (fig. 6.1).

Seed Production ________________

Reproductive Growth

Reproductive or inflorescence growth starts in late

spring to early summer and reaches its maximum rate

during late summer with florets fully developed by

late summer to early fall (DePuit and Caldwell 1973;

Evans and others 1991; Fisser 1986; Sauer and Uresk

1976). Flowering or pollination occurs during late

summer to mid-fall with fruit development commencing almost simultaneously with flowering and achenes
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 179

(dry single-seeded fruit) (Meyer 1994) maturing during midfall to midwinter (DePuit and Caldwell1973;

Everett and others 1980; Fisser 1986; Pitt and Wikeem

1990; Sauer and Uresk 1976). Thus, reproductive

growth occurs when water supplies and temperatures

are not particularly favorable; in fact, during this

period, big sagebrush plants have started shedding

ephemeral leaves from vegetative shoots and neighboring plant species are largely dormant (Miller and

others 1983). Evans and Black (1993) found, through

the use of carbon isotopes, that vegetative fixed

carbon does not transfer to reproductive structures.

Further, they found that inflorescences of big sagebrush generate positive net photosynthesis at a time

when the whole plant is in a water conservation

mode, that is, leaf abscission is occurring and stomata are exerting control over water loss. Evans and

Black (1993, p. 1524) further noted that: “Vegetative

and reproductive modules both responded to the

limited availability of water and increased evaporative demand by abscising leaves and decreasing stomatal conductance. Reproductive modules, however,

consistently had higher transpiration rates.” They

reported that supplemental watering stimulated inflorescence, but not vegetative growth (also see Carpenter and West 1988; Evans and others 1991). Evans

and others (1991, p. 676) stated:

Expanding inflorescences during summer may enhance

competitive ability because biomass can be allocated

solely toward vegetative growth during spring, increasing the capacity of Artemisia tridentata to acquire

resources when they are most abundant. Conversely,

inflorescences that are photosynthetically self-sufficient can better respond to favorable soil moisture or

intermittent precipitation during summer, because

photosynthesis can be increased without investing

resources into further vegetative growth.

Inflorescences are produced from short shoots’ terminal soft buds at the distal end of 1-year-old long

shoots (see chapter I for a detailed discussion of inflorescence morphology) (Bilbrough and Richards 1991;

Hoffman and Wambolt 1996). This allows inflorescences to be elevated, enhancing wind pollination and

wind dispersal of achenes (McArthur and others 1988;

Pendleton and others 1989). One-year-old leader, long

shoots produce more new long shoots and inflorescences than 1-year-old lateral, long shoots, making big

sagebrush less tolerant of browsing than other shrub

species (Bilbrough and Richards 1991; Wambolt and

Hoffman 2004). Therefore, browsing of current year

long shoots will reduce seed production (Booth and

others 2003; Rodriguez and Welch 1989; Wagstaff and

Welch 1990, 1991).

Seed Dispersal

The small mature achenes or seeds are wind dispersed

from midfall to midwinter; however, big sagebrush

achenes lack special structures that would aid in long

distance dispersal, 100 feet being maximum (Everett

and others 1980; Meyer 1994; Pendleton and others

1989; Pitt and Wikeem 1990; Sauer and Uresk 1976;

Welch 1999; Welch and others 1990; Young and Evans

1989). Most achenes are dispersed within 3 or 4 feet

from the mother plant, and achenes are not dispersed

evenly but are heavily influenced by wind direction.

Assuming that it takes 2 to 4 years (Young and others

1989) for a big sagebrush plant to reach maturity, it

would take about 105 to 211 years for big sagebrush to

spread 1 mile across a large grass seeding or burn.

Surviving plants would serve as a seed source that

could speed the recovery of big sagebrush from a burn

or some other disturbance (Frischknecht and Bleak

1957; Johnson and Payne 1968; Marlette and Anderson

1986).

Blaisdell (1953) speculates that big sagebrush

seeds can be dispersed with the wind across snow.

There are a number of problems with this: first, snow

and especially crusted snow is not a smooth surface,

and seeds of big sagebrush do settle into small pits,

cracks, and other surface irregularities where winds

cannot move them; second, the dark-colored seeds

absorb solar energy and melt deeply into the snow

pack (Welch 1999); and third, the seeds can be quickly

buried into the snow through a process known as

winnowing (Young and others 1990).

Evidences for persistence of big sagebrush seeds in

soil seed banks are contradictory. Hassan and West

(1986) and Mueggler (1956) found a small fraction of

viable seeds in the soil seed bank samples after a burn;

Young and Evans (1989) did not (see Meyer 1994). At

any rate, the recovery of big sagebrush from fires or

grass seedings is slow but can be speeded up through

artificial seeding as described earlier.

Seed Increase Gardens

A single mountain big sagebrush plant growing on a

seed increase garden can produce more than 500,000

achenes per year (Meyer 1994; Welch, and others

1990). Production from native stands of big sagebrush

can range from 0 achenes or seeds per acre to about 20

million seeds per acre (Young and others 1989). Achene

or seed production, however, can be influenced by a

number of factors: genetic potential expressed at the

subspecies and populations level, site differences, years

(wet versus dry), intra- and interspecific competition,

diseases, insects, excessive browsing, and plant age

(Booth and others 2004; Carpenter and West 1988;

Hoffman and Wambolt 1996; Meyer 1994; Rodriguez

and Welch 1989; Wagstaff and Welch 1991; Welch 1997;

Welch and Nelson 1995; Young and others 1989).

To obtain the necessary volume of big sagebrush

seeds for seeding onto a large disturbance where just
180 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 6.7—Comparisons of 1993 to 1995 seed production

years and vegetative measurements of Gordon

Creek Wyoming big sagebrush (Artemisia

tridentata ssp. wyomingensis) plants established

from direct seeding and from containerized stock.

Data are expressed as means ± standard deviations of grams of pure live seed (after Welch 1997).

Seed1 Containerized1

Seed production

1993 (g) 39 ± 16a 25 ± 17b

1994 (g) 34 ± 17a 9 ± 6b

1995 (g) 64 ± 23a 33 ± 10b

Vegetative measurements

Aboveground biomass (g) 2,080 ± 306a 1,531 ± 472b

Root mass (g) 946 ± 99a 679 ± 201b

Root depth (cm) 231 ± 11a 191 ± 27b

Depth to first root (mm) 38 ± 14a 71 ± 20b

Death rate (%) 0 13

1 Row means with the same superscripts are not significantly

different (p ≤ 0.05) paired t-tests.

a limited number of remnant plants exist, seed production gardens may be needed. For populations of big

sagebrush possessing desirable characteristics, seed

production gardens may also be needed (Meyer 1994;

Welch and others 1986, 1992).

Garden sites should be chosen that have deep, welldrained soils, low salt, a pH near neutral, and the

possibility of supplementing natural rainfall with irrigation water during a drought or when growing subspecies of big sagebrush that may require more water

than that provided by normal precipitation. Clean

cultivation will help to conserve moisture for the

production of seeds. For most populations and subspecies, planting on a 7- by 7-foot grid will provide enough

space for cultivation, harvesting, and other operations. However, some larger basin big sagebrush

populations may require a 10- by-10-foot grid.

As pointed out earlier, Welch (1997) compared the

seed production of big sagebrush plants established

from containerized seedlings to plants established by

direct seeding. Welch (1997) found that seed-derived

plants produced more seeds, larger top growth, deeper

roots, lateral roots nearer the soil surface, heavier root

systems, and a lower death rate than container-derived plants (table 6.7). Therefore, bareroot or container-derived big sagebrush plants may not perform

as well as seed-derived big sagebrush plants. Also,

seed increase gardens must be protected from browsing ungulates because browsing will reduce the number of seed stalks and overall plant vigor (Rodriguez

and Welch 1989; Wambolt and Sherwood 1999).

Big sagebrush seed increase gardens can be established by hand placing five to 10 seeds on a firm soil

surface and then carefully pressing the seeds into the

soil by stepping on them with a smooth-soled shoe.

Yields from these gardens should range from 40 to 70

pounds of pure live seed per acre in 2 to 3 years (Welch

and others 1990).

As a cautionary note, care must be exercised when

collecting big sagebrush seeds to be used in the establishment of seed increase gardens. Hild and others

(1999) studied characteristics of seedlings derived from

maternal Wyoming big sagebrush plants occupying

upslope, core, and downslope positions. They found that

these seedlings differed significantly in a number of key

growth characteristics. Sampling across ecotones may

not be desirable (see chapter V for more details).

Harvesting and Cleaning Big Sagebrush

Seed

Harvesting—Nearly all big sagebrush seed sold

have been collected from wildland stands (Meyer 1994).

It is important that the stand location be clearly noted

so that seeding sites may be matched to the characteristics of the collection site as noted earlier.

Seeds are usually harvested by beating the inflorescences with a wooden paddle or tennis racket, which

detaches the achenes or seeds from the seed heads and

drives them into canvas hoppers or other containers

(Deitschman 1974; Plummer and others 1968; Shaw

and Monsen 1990; Wasser 1982). Achenes cannot be

detached from the seed heads with tennis rackets or

wooden paddles until they have reached the proper

degree of maturity, or dryness. Thus, potential collection sites must be checked several times to ensure

readiness, which can vary from the first of October to

the end of December, depending on subspecies, population, weather conditions, and so forth (Payne 1957).

If collections are attempted too soon, achenes are not

harvestable; if too late, some of the achenes have

shattered. Under certain circumstances, it may be

necessary to harvest before the achenes are mature

enough to detach them from the seedheads. In this

case, entire inflorescences may be removed or clipped.

When this is done care must be exercised to avoid the

buildup of heat and humdity within inflorescence

storage piles. When the immature embryos are tan

color, inflorescences may be clipped without shrinkage or damage to unripened achenes. It is extremely

important to dry all material collected to less than 9

percent moisture as quickly as possible, regardless of

harvesting technique (Welch and others 1996). Drying big sagebrush seed during the cold, wet weather

of the harvesting period creates special challenges

for commercial suppliers that can only be solved by

the use of forced-air driers (Welch and others 1996).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 181

Big sagebrush achenes can tolerate temperatures up

to 140 °F (Payne 1957; Welch 1996). After proper

drying, the next step is cleaning.

Seed Cleaning—The first step in cleaning of big

sagebrush achenes or seeds is to pass the harvested

mixture of inflorescences, achenes, seed bracts, small

twigs, leaves, and so forth through a debearder. Welch

(1995) and Booth and others (1996a,b) reported that

passing achenes or seeds through a debearder does not

damage the achenes or lower seed germination or

viability. This is illustrated in table 6.8. It is clear from

the data presented in this table that seed viability was

not adversely affected even with two passes through

the debearder; however, when the exit door was tied in

such a manner as to force harvested material through

a small opening, then and only then was seed viability

reduced (Welch 1995). Passing harvested materials

through a debearder not only aids in the thrashing of

seeds or achenes from the seedheads but also breaks

fine stems and other trash into small pieces that can

be readily removed by most commercial fanning-screening seed cleaners. A single pass of harvested material

through a debearder is enough (Welch 1995).

Welch (1995) reported that purity of 50 percent or

greater could be achieved by using a two-screened

Crippen model XV-242-LH seed cleaner with air lift.

He equipped the cleaner with a 14 by 14 mesh screen

in the top screen position and a 36 by 36 mesh screen

in the bottom position and adjusted the air lift to

maximum without picking up fully ripen achenes or

seeds. After four passes through this cleaner purities

ranged from 51 to 59 percent. This cleaning procedure

is illustrated in figure 6.2. Use of a gravity table or

Table 6.8—Effects of debearder on big sagebrush seed viability. Data expressed as a percent of live seeds (after

Welch 1995).

Percent of

viable seeds1

Experiment 1 (Wyoming big sagebrush)

Before debearder 93.3 ± 1.79a

After first debearder pass 93.0 ± 1.87a

After second debearder pass and cleaning 93.0 ± 0.71a

Experiment 2 (mountain big sagebrush)

Before debearder 87.8 ± 3.11a

After first debearder pass 89.0 ± 3.74a

After second debearder pass and cleaning2 40.8 ± 8.26b

1 Means and standard deviations sharing the same superscripts in

columns of the same experiment are not significantly different (p < 0.05). 2 This experiment was conducted in the same manner as experiment

1, except when the mixture of seeds, achenes, and so forth, were

passed through the debearder the second time the exit door was tied

so the material could exit only a small opening (about 10 percent of the

usual opening). Materials that passed through the debearder a second

time were warm to the touch. This treatment exposed the seeds to the

maximum harshness of the debearder.

Figure 6.2—A flow chart outlining the movement of

a big sagebrush seed lot, weighing 107.35 lbs,

through an air/screen seed cleaner. Before cleaning, the seed lot was passed once through a

debearder. Trash was separated from seeds by

being carried over a 14-by-14 mesh screen, being

air lifted from the seed, passing through a 36-by-36

mesh screen, or being lost as flying dust. The final

product was obtained by running the material carried off the 36-by-36 mesh screen five time through

the seed cleaner. Final product had a purity of 65.9

percent and a seed viability of 93 percent (after

Welch 1995).
182 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Table 6.9—Viability of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) seed stored at different humidities

and for various lengths of time. Data expressed as means and standard deviations of the percent of live seed

as determined by tetrazolium staining method. Three replications per humidity-time cell; 300 seeds tested per

replication. Starting (0 days) viabilities were compared to the various humidities and times by unpaired, uppertailed T-test (p = 0.05) (after Welch 1996).

Percent humidity

Days 01 Open2 32 45 56 66 86 100

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Viability3 (percent) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

0 90 ± 0.8a 91 ± 1.4a 92 ± 0.9a 91 ± 1.3a 92 ± 1.6a 91 ± 0.5a 91 ± 2.2a 92 ± 0.0a

60 90 ± 0.5a 91 ± 2.2a 91 ± 2.5a 93 ± 2.5a 64 ± 0.5b 6 ± 1.7b 0 0

120 86 ± 2.5a 91 ± 2.7a 91 ± 3.7a 92 ± 1.6a 57 ± 5.8b 0 00

180 86 ± 2.3a 89 ± 1.7a 90 ± 1.7a 90 ± 2.5a 51 ± 1.9b 0 00

240 90 ± 0.4a 91 ± 2.6a 92 ± 1.3a 88 ± 2.6a 54 ± 3.4b 0 00

300 90 ± 0.0a 89 ± 0.8a 89 ± 2.6a 86 ± 3.7a 24 ± 3.7b 0 00

360 92 ± 2.1a 93 ± 2.8a 93 ± 1.9a 89 ± 1.2a 00 00

1 Zero humidity = seeds stored over regenerated anhydrous calcium sulfate.

2 Open = seeds stored in open containers in a growth chamber (humidity about 26 percent).

3 Values in columns with an a are not significantly different from the starting (0 days) seed viability. Those with a b or 0 are significantly

different from the starting (0 days) seed viability.

other equipment can increase purity to 80 percent or

greater (Welch 1995)—purities greater than published

standards of 8 to 12 percent (Stevens and Meyer 1990).

Purities greater than the standard of 8 to 12 percent

save money well beyond the extra cost of cleaning the

seed lots (Welch 1995) by reducing the amount of

material that needs to be handled, stored, and shipped.

For example, 1,000 pounds of pure live big sagebrush

seed at 50 percent purity and 80 percent seed viability

would weigh 2,500 pounds compared to 10,417 pounds

for the same weight of pure live seed at 12 percent

purity and 80 percent viability. Welch (1995) estimated a savings of at least $1,176 in shipping, storage,

and handling costs at the higher purity with a sizable

reduction in the amount of dust produced when handling the seed sacks. Also, less material would be

required to pass through planting equipment when

seeding at higher purities.

Seed Storage

After seed cleaning, storing the seed under proper

conditions is absolutely critical to be able to maintain

high levels of viability (75 percent) and for many years (at

least 9 years) (Welch and others 1996). Humidity is the

enemy of stored seeds (Welch 1996) (table 6.9). Welch

(1996) concluded that big sagebrush seeds should not be

stored in environments with humidities over 40 percent.

Welch and others (1996) studied the effects of storing

big sagebrush seeds at constant humidity (20 percent)

but in three environments: cool, constant temperature

(refrigerator 50 °F); room temperature (58 to 76 °F);

and a nonheated warehouse (–18 to 112 °F). They

found a significant drop in seed viability occurred first

in the seed lots stored in the nonheated warehouse and

then in seeds stored at room temperatures (table 6.10).

Seed viability stored in a cool environment dropped

the least. Even in the nonheated warehouse, high seed

viability (75 percent or more) was maintained for 6

years; and 7 years for seed stored at room temperature; and 9 years for seeds stored at a constant cool

temperature of the refrigerator (table 6.10). These

storage years of high seed viability compare to the

reports of Hull (1973), Stevens and others (1981), and

Stevens and Jorgensen (1994) of 2 and 3 years.

The keys to storing big sagebrush seeds at high

levels of viability beyond 3 years are: drying to a

minimum of 9 percent, reducing seed moisture as soon

as possible after harvesting, and storing in a dry

environment with less than 40 percent humidity and

with low constant temperature. Bewley and Black

(1985) noted that seed moisture content greater than

30 percent would cause nondormant seed to germinate

in storage and that moisture contents between 18 to 30

percent caused rotting of seeds by microorganisms.

They further explained that seeds stored at 18 to 20

percent will respire but seeds stored below 8 to 9

percent moisture will not respire and will not be

attacked by insects. Haws and others (1996) found

that 6 to 45 percent of big sagebrush seeds from 26 seed

lots examined were damaged by insects, perhaps due

to storing big sagebrush at a high moisture content.

Bewley and Black (1985, p. 392) stated: “below 4-5%

moisture content seeds are immune from attack by

insects and storage fungi, but they may deteriorate

faster than those maintained at a slightly higher

moisture content. The activities of seed storage fungi

are ultimately more influenced by the RH (relative

humidity) of the inter-seed atmosphere than by the

moisture content of the seeds themselves.”
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 183

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Table 6.10—Big sagebrush seed viability under three storage

environments with humidity held constant at 20

percent. Cool storage was in a refrigerator 50 °F

with little temperature fluctuation. Room storage

was in a heated and air-conditioned room with

temperature fluctuation about 18 °F. Warehouse

storage was in a nonheated warehouse where

temperatures fluctuated about 130 °F. Data are

expressed as means and standard deviations of

the percent of live seed (after Welch and others

1996)

Year Cool1 Room1 Warehouse1

1986 96.7 ± 1.5a 96.3 ± 1.2a 96.0 ± 1.6a

1987 97.2n ± 1.4a 95.5n ± 2.2a 97.8n ± 1.1a

1988 96.2n ± 2.0a 96.3n ± 1.8a 87.3 ± 4.82

1989 96.3n ± 1.6a 96.0n ± 1.9a 95.7n ± 1.7a

1990 95.7n ± 2.0a 95.2n ± 1.8a 93.5n ± 1.9a

1991 96.5n ± 1.9a 95.1n ± 2.3a 91.9s ± 4.2b

1992 95.2n ± 2.2a 94.6n ± 1.9a 89.3s ± 4.7b

1993 95.5n ± 2.1a 81.2s ± 16.3b 71.8s ±12.3c

1994 93.8s ± 2.1a 70.2s ± 17.2b 51.0s ±17.5c

1995 92.1s ± 3.3a 53.8s ± 20.2b 25.9s ±14.5c

1 Means in rows sharing the same superscripts are not significantly

different at the 5 percent level.Means in columns with an n are not

significantly different at the 5 percent level from the 1986 seed viability.

Those with an s are significantly different. 2 An anomaly in the data set, cause unknown.
184 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

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USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 187

Chapter

VII

Consequences of

Controlling Big Sagebrush

Reflecting on a previous publication of mine (Welch 2002, p. 6), I noted that: “I have

never liked the term controlling big sagebrush because it infers that big sagebrush is out

of control. Who has the ecological insight to determine when big sagebrush is out of

control?” In this chapter, I explore the ecological and political issues of managing big

sagebrush and what has happened ecologically when there have been efforts to control

the species.

A brief look at attitudes toward big sagebrush found in the literature sets the stage.

Welch (1999) pointed out that for the six range management textbooks he read (Heady

1975; Heady and Child 1994; Holechek and others 1989; Stoddart and others 1975;

Vallentine 1989, 1990), 68 percent of the comments made concerning big sagebrush he

considered negative, including: “unpalatable to livestock,” “high levels of volatile oils,”

“invader,” “undesirable,” “reduces the production of better plants,” “causes rumen

disorders,” “uses up water,” “woody,” “noxious,” “poisonous,” “low value,” “little used,”

“control,” “eradicate,” “convert,” “suppress grasses,” and so on. Only 9 percent of the

comments on big sagebrush were positive, including: “provide mule deer (Odocoileus

hemionus hemionus), pronghorn antelope (Antilocapra americana), and domestic sheep

(Ovis aries) with winter feed,” “food for jack rabbits (Lepus californicus),” “food for sage

grouse (Centrocercus urophasianus),” and “nesting sites for Brewer’s sparrow (Spizella

breweri).”

Such contrasting views continue today, and the negative attitudes are used to justify

the killing of big sagebrush. However, Peterson (1995, p. 38) concluded: “Removing

sagebrush in an effort to improve forage for livestock does not automatically equate to

benefits for wildlife.” And Fischer and others (1996) noted that their research findings

did not support the idea that killing big sagebrush through the use of fire enhanced sage

grouse brood-rearing habitat.

Upon Euro-American settlement of the Western United States, the rationale for

destroying big sagebrush was directly related to enhancing the livestock industry, or as

Vallentine (1989, p. 1) states: “Range improvements are special treatments, developments, and structures used to improve range forage resources or to facilitate their use

by grazing animals. Range seeding, control of undesirable range plants [big sagebrush

being one], applying fertilizer, and pitting, furrowing, and waterspreading are direct
188 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

means of developing and improving range forage resources.” Further, Vallentine (1989, p. 58) lists big

sagebrush as one of the individual problem plants.

West and Hassan (1985, p. 131) stated: “If fire destroys

a large fraction of the undesirable brush and is relatively undamaging to the desired herbaceous species,

then a landscape that is better for livestock production

and water shed may be created.” However, many

wildlife species depend on big sagebrush including

sage grouse, Brewer’s sparrows, sage sparrows

(Amphispiza belli), sage thrashers (Oreoscoptes

montanus), pygmy rabbits (Brachylagus idahoensis),

sagebrush vole (Lagurus curtatus), 52 species of aphids,

and so on (see chapters II and III).

There are some signs that a different philosophy and

policy are emerging. For example, the USDI Idaho

Bureau of Land Management lifted its ban on the

planting of big sagebrush in the mid-1980s and today

is purchasing tens of thousands of pounds of big

sagebrush seed to be used on fire rehabilitation projects.

Also, the USDI Utah Bureau of Land Management is

encouraging higher big sagebrush production on critical mule deer winter range by allowing heavy livestock

grazing (Wambolt and Watts 1996). And there is this

statement of Heady and Child (1994, p.301), authors of

a range management textbook: “The word ‘undesirable’ is difficult to eliminate from a discussion of

vegetational modification because a plant may be both

desirable and undesirable depending upon the use to

be made of it. One example, Artemisia ssp. in thick

stands are generally undesirable for livestock but

furnish food and cover for wildlife species.”

Negative Impacts of Big Sagebrush

Control ________________________

Daubenmire (1970) listed six concerns he has with

big sagebrush control. These six concerns are discussed here, with additional observations by other

researchers.

First concern is that increase in grass production is

not a long-lived phenomenon and could be the effect of

dead big sagebrush roots supplying a greater quantity

of nutrients—that is a “green-manure effect.”

Daubenmire points out that fire itself stimulates grass

production. Thilenius and Brown (1974) observed: “On

three summer cattle ranges in the Bighorn increased

herbage production after sagebrush control with 2,4-

D was a relatively short-lived phenomenon. Declines

in production and in the proportion of graminoids in

the herbage did not appear to be related to reinvasion

of sagebrush as this was minimal on all three sites

even after 10 to 11 years.” Also, Clary and others

(1985) reported no significant increase in the production of perennial grasses in spite of a significant

reduction in shrub production (mainly mountain big

sagebrush, killed by tebuthiuron treatments) of some

73 to 99 percent.

The second concern is that, by its physical presence

alone, big sagebrush protects grass from total destruction, and elimination of big sagebrush could lead to the

total destruction of grass during periods of overgrazing such as during a drought. Pechanec and Stewart

(1944a, p. 1) observed: “Even when they [livestock]

force their way into the shrubby growth, half the

palatable grasses and weeds beneath the sagebrush

are likely to be unavailable to them.”

The third concern is about fertility of the earth. Due

to the deep-rooted nature of basin and mountain big

sagebrush (Artemisia tridentata ssp. tridentata and

vaseyana) and in some locations Wyoming big sagebrush (A. t. ssp. wyomingensis), islands of fertility are

formed across the land by extracting minerals far

deeper in the soil profile than grasses or forbs can.

Sagebrushes’ constant removal could easily affect soil

fertility and grass production itself.

Fourth, controlling big sagebrush can destroy wildlife habitat of birds, small mammals, reptiles, insects,

spiders, and so forth, that depends upon big sagebrush.

Fifth, some big sagebrush controlling projects use

herbicidal sprays that kill nontarget plant species

such as broadleaf forbs.

And sixth, big sagebrush helps to promote the uniform accumulation of snow, deeper depth of snow,

delays its melting, and retards the development of ice

sheets, thus benefitting deep soil water storage (also

see Hutchison 1965).

Daubenmire (1970, p. 79) summarized:

The more diversified the biota of an area, the more

completely the environmental resources are being used,

and the better the community is buffered against disease and weather hazards. Simplification of shrubsteppe vegetation by removing a major component that

contributes a distinctive life-form and phenology, and

is necessary for other species to remain in the community, cannot fail to have significant consequences.

One of these consequences is expressed by Nelle and

others (2000, p. 586): “No benefits for sage grouse

occurred as a result of burning sage grouse nesting

and brood-rearing habitats. Burning created a longterm negative impact on nesting habitat because sagebrush required over 20 years of postburn growth for

percent canopy cover to become sufficient for nesting.”

(Also see the following supporting articles by Benson

and others 1991; Connelly and others 2000; Fischer

and others 1996.) Further, Kochert and others (1999)

noted that the burning of big sagebrush had a negative

effect on golden eagles (Aquila chrysaetos) in southwestern Idaho.

Pechanec and others (1965) noted that plant species

such as rabbitbrush (Chrysothamnus spp.), horsebrush
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 189

(Tetradymia ssp.), cheatgrass (Bromus tectorum), and

halogeton (Halogeton glomeratus) may increase sharply

after big sagebrush control. They caution (p. 4): “Care

must be taken in sagebrush control work to avoid

exchanging one problem for a more difficult one.”

Figure 7.1 illustrates this possibility, where just

west of Trout Creek located in the Strawberry Valley

of central Utah, land managers conducted a prescribed

burn during the fall of 1999. In the fall of 2000,

following the 1999 fall burn, I constructed a belt

transect 400 feet by 2 feet starting at the photo point

of figure 7.1. Half the transect was in the burn area

and half in the mountain big sagebrush stand. Canopy

cover of mountain big sagebrush exceeded 30 percent.

Within this transect, I counted, in the burned proportion, 37 (36 in 2003) musk thistle plants, all at the

rosette stage of development (fig. 7.2), meaning that

the plants had established themselves during the

spring of 2000 and would bolt and flower the following

summer of 2001. In the mountain big sagebrush stand,

I counted two (five in 2003) small rosette plants. The

burn had the undesirable effect of increasing the

distribution and abundance of a noxious weed.

Figure 7.1—A view (north to south) along a 400 ft by 2 ft belt transect from a prescribed fire (fall 1999) of

mountain big sagebrush (Artemisia tridentata ssp. vaseyana) into unburned mountain big sagebrush having

a canopy cover greater than 30 percent. The prescribed fire was located just west of Trout Creek in the

Strawberry Valley of central Utah. Two hundred feet of the transect was in the burned area and the remaining

200 feet was in the unburned area. The burned portion of the transect contain 37 plants in 2000 and 36 in 2003

of the noxious weed musk thistle (Carduus nutans) and unburned area 2 small plants in 2000 and 5 in 2003

(photo by Bruce L. Welch fall 2000).
190 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Does Killing, Thinning, or

Controlling Big Sagebrush Increase

Grass Production? ______________

Kissinger and Hurd (1953) and Hedrick and others

(1966) studied the improvement of perennial grass

production by killing big sagebrush. I interpreted

their findings as comparing grazed-out big sagebrush

plots, to treated plots, with treated plots showing a

substantial gain in perennial grass production—some

two or threefold or more increase. The conclusions

from these and many like studies were that big sagebrush suppresses perennial grass production. Yet, the

possible contribution of poor grazing practices in suppressing perennial grass production has not been

factored out. A comparison between treated big sagebrush plots and nongrazed big sagebrush plots would

help to ascribe how much of the observed perennial

suppression was due to the presence of big sagebrush

and how much was due to poor grazing practices.

Do we have data available to allow for such a comparison. Yes, to a limited degree. In table 7.1, I have

listed the results of 29 studies that were conducted to

determine the amount of perennial grass production

that was achieved by killing big sagebrush by various

means, on varying sites, and for varying lengths of

times after treatment. Some of the studies involved

seeding perennial grasses (mostly nonnative) and forbs

after the treatments, and others did not. Table 7.2

displays the production of perennial grasses on

ungrazed kipukas and relicts from the study of Passey

and others (1982). Data in both tables are based on

pounds of air-dried perennial grass forage per acre.

The yearly means (1, 2 to 3, 4 to 5, 6 or more years after

treatment) for the 29 studies were 283, 421, 609, and

438 pounds. The range for these studies was 42 to

1,805. These values compare fairly close with the

overall mean of 455 and range of 90 to 1,169 for the

Passey and others (1982) study of ungrazed kipukas

and relicts (also see, Passey and Hugie 1963; Pechanec

and Stewart 1949). These data support the proposition

Figure 7.2—A closeup view in the burned area of figure 7.1 showing at least 7 plants of musk thistle (Carduus nutans)

and a few blacken stump of mountain big sagebrush (Artemisia tridentata ssp. vaseyana); (photo by Bruce L. Welch

fall 2000).
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 191

Table 7.1—Production of perennial grass on big sagebrush (Artemisia tridentata) controlled plots. Data expressed as pounds

per acre of air-dried grass. Perennial grass production was grouped according to number of years after treatment

1, 2 to 3, 4 to 5, and 6 years or more.

Perennial grass production Big sagebrush

Study Treatments 1 2–3 4–5 6+ Study range subspecies

lb/acre

Baxter 1996 Teb 495 — —

Olson and others 1996 Teb 725 582–819 —

Halstvedt and others 1996 Teb 536 368–750 —

Kay and Street 1961 24D 970 90–970 —

Miller and others 1980 24D 267 550 — — Mountain

615 579 — — Mountain

Clary and others 1985 Teb 218 524 — — 135–885 Mountain

Sturges 1986 24D 281 426 347 — 261–521 Mountain

Wambolt and Payne 1986 Burn 206 240 382 379 93–672 Wyoming

24D 162 550 428 289 157–664 Wyoming

Plow 144 255 365 200 74–540 Wyoming

Rotocut 145 331 333 200 88–567 Wyoming

Murray 1988 Teb — 331 493 — 160–605 Mountain

Thilenius and Brown 1974 24D ——— 267 174–359 —

Evans and Young 1975 24D 276 503 508 — 339–677 —

24D+Picl 588 913 1274 — 588–1381 —

Robertson 1969 24D 143 450 1163 — 143–1163 —

291 429 798 — 291–798 —

Johnson 1969 24D — 253 187 255 182–294 —

Tabler 1968 24D 310 400 800 410 — —

Hedrick and others 1966 24D 375 343 743 358 300–910 —

Rotobeat 388 405 643 276 285–725 —

Peek and others 1979 Burn 85 215 — — — Wyoming

West and Hassan 1985 Burn 80 259 — — — Wyoming

Alley 1956 24D — — — — 769–1347 —

Schumaker and Han. 1977 24D — 259 — — — Wyoming

Grubbed — 308 — — — Wyoming

24D — 411 — — 400–473 Mountain

Grubbed — 412 — — 400 –424 Mountain

Tueller and Evans 1969 24D — 325 461 517 110–910 —

Picoram — 308 971 510 250–1805 —

Olson and others 1994 Teb ——— 724 582–819 —

Miller 1957 24D — 780 — — — —

Kissinger and Hurd 1953 245T — 530 — — 460–590 —

Hyder and Sneva 1956 245T 501 324 — — — —

Grubbed 474 333 — — — —

McDaniel and others 1991 24D 442a 338a — 554a 327–554a Wyoming

Metsulfuron 510a 716a — 558a 315–1185a Wyoming

McDaniel and others 1992 Teb — 6781 540a 492a 42–1344a Wyoming

Raper and others 1985 Burn 192 — — — 144–240 Mountain

Blaisdell 1953 Burn ——— 305 290–321 Mountain

Burn — — 367 — 365–369 Wyoming

Harniss and Murray 1973 Burn 139 448 — 254 — Wyoming

Means 283 421 609 438 (42–1805) —

a

 Values based on total herbaceous standing crop.
192 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

that ungrazed or undisturbed big sagebrush sites

produce about the same amount of perennial grasses

as treated sites where the big sagebrush has been

destroyed. Big sagebrush canopy cover of the kipukas

ranged from 14 to 34 percent (table 4.14; see chapter

IV for a discussion concerning big sagebrush canopy

cover and grass production).

Peterson (1995, p. 34) has suggested that: “Sagebrush is a product of the range, range condition is not

a product of sagebrush.” Differences in perennial grass

production in big sagebrush stands have less to do

with shrub cover than it has with soils, moisture (wet

or dry years), grass species, and especially grazing

history differences (Peterson 1995; Pechanec and others 1937; Pechanec and Stewart 1949; Piemeisel 1945).

Johnston (2003) observed: “CCOV (canopy cover of big

sagebrush) is not significantly correlated (at ∝ = 0.05

or 0.01) with either graminoid cover, forb cover, or

bare soil cover.” Thilenius and Brown (1974) observed:

“On three summer cattle ranges in the Bighorn increased herbage production after sagebrush control

with 2,4-D was a relatively short-lived phenomenon.

Declines in production and in the proportion of

graminoids in the herbage did not appear to be related

to reinvasion of sagebrush as this was minimal on all

three sites even after 10 to 11 years.” Sneva’s (1972)

figure 2 shows a close relationship between herbage

production and precipitation. In fact r and R2 values

are high at +0.9649 and 0.9311, respectively. Passey

and Hugie (1963) noted on an ungrazed kipuka dramatic difference in the yield of perennial grasses and

forbs on different soils within the kipuka. The Brunt

silt loam soil yields 227 pounds of herbage per acre

compared to 524 pounds of herbage per acre of the

Newdale silt loam soil. Precipitation was slightly below average during the study period. So, it appears

that the recurrence of perennial grass after big sagebrush control may be a reestablishment of potential

grass production, without big sagebrush.

The Harniss and Murray (1973) report is often cited

by those trying to justify the use of fire to improve

grass production in the big sagebrush ecosystem. If

you read and study just the figures or graphs in their

report, it appears fairly obvious that burning big

sagebrush increases grass yield substantially. Their

figures or graphs are constructed based on four data

points of vegetation production for the years 1937,

1939, 1948, and1966, all of which are related back to

the so-called base year of 1936 or 100 percent. I do not

believe that four data points representing 30 years of

vegetative growth constitute an adequate sampling

size, nor is expressing the data in relative terms of the

1936 year or 100 percent appropriate because weather

conditions vary greatly among years. In fact, Pechanec

and Stewart (1949, p. 23) noted: “Records from these

range pastures and from detailed plot studies showed

Table 7.2—Production of perennial grasses, forbs, and total herbage on ungrazed kipukas and relict

areas as determined by Passey and others (1982). Data expressed as pounds of air dried

forage per acre and represents a 10-year mean, with arithmetic range in parentheses per

exhibit or stand.

Exhibit or Big sagebrush 10-year mean 10-year mean 10-year mean

stand subspecies grasses lbs/acre forbs lbs/acre herbage

3A Basin 563 (301–901) 131 (79–206) 694

4A Basin 544 (245–781) 120 (42–211) 664

6A Wyoming 160 (90–300) 92 (13–246) 252

8A Basin 790 (435–1149) 212 (100–504) 1002

9A Basin 453 (168–764) 181 (45–331) 634

10A Basin 672 (347–1169) 166 (37–337) 838

11A Wyoming 390 (225–713) 172 (51–289) 562

12A Wyoming 369 (195–553) 205 (58–398) 574

13A Wyoming 426 (266–632) 80 (5–173) 506

14A Wyoming 299 (152–424) 65 (15–164) 364

15A Basin 665 (362–1033) 100 (28–189) 765

16A Wyoming 439 (271–612) 296 (175–463) 735

17A Wyoming 307 (171–420) 138 (54–223) 445

18A Wyoming 316 (208–480) 200 (122–290) 516

19A Wyoming 426 (288–732) 180 (53–304) 606

Means Basin 616 (168–1169) 152 (28–504) 767

Wyoming 348 (90–732) 159 (5–463) 507

Overall 455 (90–1169) 156 (5–504) 611
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 193

that not until 1937 had perennial bunchgrasses fully

recovered from the effects of the 1934 drought.” My

interpretation of their (Harniss and Murray 1973)

table 1 suggests an interesting contradiction to their

figures. While their figures may portray accurately

the relationship of grass production of 1936 to the

other 4 years, I do not think they accurately represent

the effects of burning or the killing of big sagebrush on

grass production. Their table 1 shows that half of the

data points of the unburned plots (1937 and 1966)

produced more grass than burned plots, yet big sagebrush production was substantially lower in the burned

plots that produced less grass. It should be pointed out

that during 1966, precipitation was 75 percent of the

long-term average (NOAA 1966) and that they cannot

separate the alleged negative effects of big sagebrush

on grass production from the negative effects due to

drought. Also, there is a high probability that Harniss

and Murray (1973) misidentified the big sagebrush in

the study area; 11 inches of annual precipitation is

more characteristic of Wyoming big sagebrush than

mountain big sagebrush (Blaisdell 1953; see chapter I

for details).

Peterson and Flowers (1984, p. 7) used a simulation

model to predict the effects of fire on range production

(grasses and forbs) in a number of ecosystems. One

model was for the sagebrush ecosystem. They state:

“The information used to simulate the effects of fire on

sagebrush range is derived from long-term studies on

sagebrush-grass range in Idaho (Blaisdell 1953,

Harniss and Murray 1973, Mueggler and Blaisdell

1958) and Oregon (Hedrick and others 1966, Sneva

1972).” However, two of these five studies used for

their model development were not burns. Both Oregon

studies used 2,4-D to kill big sagebrush. The relationship between burning big sagebrush stands and spraying with 2,4-D is unknown.

In their model, Peterson and Flowers (1984) chose a

prefire production level of 280 pounds of grasses and

forbs per acre and a gain of 800 pounds of grasses and

forbs per acre until sagebrush allegedly establishes

dominance and reduces herbaceous production to the

prefire level. In my opinion, there are a number of

erroneous assumptions that the authors made in developing their model. First, the 280 pounds per acre of

grasses and forbs probably reflects the production of

degraded big sagebrush stands. If they had used the

study average of Passey and others (1982) conducted

in ungrazed big sagebrush stands, the prefire production level would have been 611 pounds of grasses and

forbs per acre instead of the 280 pounds. Second, study

average production of grasses and forbs for the five

studies cited were: Blaisdell (1953), 507 pounds per

acre for his Fremont County site and 512 pounds per

acre for his Clark County site; Harniss and Murrary

(1973), 534 pounds per acre for 1939, and 508 pounds

per acre for 1948; Mueggler and Blaisdell (1958), 602

pounds per acre; Hedrick and others (1966), 438 pounds

per acre; and Sneva (1972), about 681 pounds per acre.

The Peterson and Flowers (1984) postfire production

of 800 pounds per acre seems much too high (the

average of the studies cited above is 540 pounds per

acre). Third, the authors did not build into their model

the effects of precipitation on grass and forb production. Holecheck and others (1989, p. 21) state: “Precipitation is the most important single factor determining

the type and productivity of vegetation in an area.”

This relationship is illustrated in the Sneva (1972)

citation. In fact r and R2 values are high at +0.9649 and

0.9311, respectively. If the authors (Peterson and

Flowers 1984) had analyzed grass and forb yield for

the years 1963 to 1969, where Sneva (1972) claimed

that big sagebrush was reestablishing itself on the

sprayed plots to the years 1954 to 1962, they would

have discovered that the mean yields under the influence of big sagebrush was 680 pounds per acre as

compared to 672 pounds per acre with reduced big

sagebrush.

A common practice before a prescribed fire is to rest

the proposed treatment area from livestock grazing

for a year or two, to allow the buildup of fine fuels

(grasses and forbs); or in other words, grasses and

forbs increase in pounds per acre and/or cover without

prekilling big sagebrush (Bunting and others 1987).

This could be considered as range improvement without killing big sagebrush.

Peek and others (1979), in their table 3, show no

significant increase in grass production 1, 2, and 3

years after a burn on Wyoming big sagebrush winter

range. Similar results occurred in the study conducted

by Raper and others (1985) 1 year after a burn in

mountain big sagebrush. West and Hassan’s (1985)

report in their table 2 shows that perennial grass

production decreased after wildfire. Blaisdell (1953)

found no significant increase in total perennial grass

production due to burning, 15 years after the burn, on

his Fremont County site but did detect a significant

increase in total perennial grass production due to

burning, 12 years after the burn, on his Clark County

site. Out of 12 data points, four sites and 3 years, Cook

and others (1994) found that perennial grass yields

were higher on burned sites versus unburned sites six

times for 50 percent. Wambolt and others (2001, p.

243) studying 13 burned sites versus paired unburned

sites in Montana noted: “Total perennial grass canopy

coverage was not different (P< 0.05) between treatments over the 13 sites. Managers considering prescribed burning of big sagebrush communities should

be aware that herbaceous plant responses may be

minimal while shrub values will likely be lost for many

years.” Even where overall grass production has shown

an increase, certain important species for wildlife and
194 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

livestock (Idaho fescue, Festuca idahoensis) are frequently reduced (Peterson 1995).

Several studies showed that total vegetative production—that is, pounds of air-dried forage for all classes

of plants—is reduced with big sagebrush control

(Blaisdell 1953; Britton and Sneva 1983; Harniss and

Murray 1973; Mueggler and Blaisdell 1958; Murray

1988; Pechanec and Stewart 1944a,b; Schumaker and

Hanson 1977; Sturges 1986; Tabler 1968). Sites with

big sagebrush are not only more productive, but the

big sagebrush itself is important for the entire vegetative community by providing protection for understory

plants, storing more snow, improving soil conditions

at greater depth through root decay, and recycling

deep soil moisture and nutrients (Peterson 1995; see

also chapter IV).

There are natural abiotic and biotic forces at work in

all big sagebrush stands that affect shrub density and

age structure over time. See previous chapters for

discussion of most of these natural agents, such as

Aroga moth (Aroga websteri), leaf beetles (Trirhabde

pilosa), snow mold, wilt diseases, voles, mule deer, and

so forth (Austin and Urness 1998; Ganskopp 1986;

Gates 1964; Hall 1963; McArthur and others 1988;

Mueggler 1967; Nelson and Krebill 1981; Nelson and

Sturges 1986; Partlow and others 2004; Pringle 1960;

Smith 1949; Sturges 1989; Wambolt and Hoffman

2004). These agents act to create interspaces within

the big sagebrush stand where new seedlings can be

established, thus resulting, if given enough time, in a

multiage stand that contains more diversity.

Does Killing, Thinning, or

Controlling Big Sagebrush Increase

Biodiversity? ___________________

Olson and Whitson (2002, p. 146) observe: “Late

successional, dense Artemisia tridentata (big sagebrush) stands restrict associated plant species production, resulting in a monotypic, shrub-dominated community that threatens biodiversity preservation and

ecosystem function.” This statement raises three issues: (1) dense stands of big sagebrush reduce yields of

associated plant species, meaning grasses and forbs;

(2) dense stands reduce biodiversity; and (3) big sagebrush is a highly competitive, dominating, suppressive plant species.

The effect of big sagebrush canopy cover on grass

production has been addressed in an earlier section of

this chapter and also in the big sagebrush canopy

cover versus bare ground cover and perennial grass

cover section in chapter IV. The second and third

issues listed above will be addressed here.

Olson and others (1994) reported that in their big

sagebrush control plots, the number of plant species

increased by three to four species over untreated big

sagebrush plots. However, they did not name the plant

species and their origins, so we do not know if they

were desirable or undesirable species. Other questions arise. Are their comparisons between overgrazed

big sagebrush sites versus treated sites proper, or

should the comparisons be between undisturbed or

never grazed by livestock big sagebrush sites versus

treated sites?

Should the measurement of biodiversity be determined only on number of plant species present or on

total number of species of all life forms? Killing of big

sagebrush certainly reduces the frequency and perhaps the number of lichen species in a treated area,

thus resulting in a loss of biodiversity. In chapters II

and III of this manuscript we see that a host of

organisms feed directly and indirectly on big sagebrush, including large and small mammals, birds,

insects, fungi, parasitic vascular plants, and so forth—

definitely an expression of biodiversity.

I calculated correlation coefficients and coefficients

of determination for the data (plant community composition) published in Tart (1996), including data

between canopy cover of mountain big sagebrush and

number of perennial grass species, number of forb

species, and total number of plants (table 4.15). No

significant relationships were detected. In the Tart

(1996, p. 42) study is found a description of a mountain

big sagebrush community with a canopy cover of 46

percent with 48 species of grasses and forbs; this

compares to a description of a mountain big sagebrush

community with a canopy cover of 17 percent with 33

species of grasses and forbs (his p. 26). On his page 74

is a description of a mountain big sagebrush community with a canopy cover of 17 percent with 35 species

of grasses and forbs.

The Goodrich and Huber (2001) study also demonstrates a lack of relationship between big sagebrush

canopy cover and number of grass and forb species:

31-4-exclosure 32.4 percent big sagebrush canopy

cover-41-grasses & forbs-46-total plants,

32-66-grazed 16.4 percent big sagebrush canopy

cover-38-grasses & forbs-41-total plants,

32-67-grazed 15.1 percent big sagebrush canopy

cover-44-grasses & forbs-47-total plants,

31-35A-grazed 5.0 percent big sagebrush canopy

cover-43-grasses & forbs-46-total plants,

32-78-grazed and burned 0.2 percent big sagebrush canopy cover-42- grasses & forbs-46 total

plants.

Perryman and others (2002, p. 419) studying the

response of vegetation to prescribed fire in Dinosaur

National Monument, Utah, found: “ Mean number of
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 195

[plant] species on combined control and burn areas

were 17 and 18, respectively.” Only one comparison

out of 20 showed a significant increase in number of

plant species for the burned site versus the unburned

site. Tiedeman and others (1987) and Baker and

Kennedy (1985) reported similar results. It appears

highly unlikely that dense big sagebrush canopy cover

suppresses or reduces biodiversity.

Big sagebrush is the mother of biodiversity. It is

what supports life in Bailey’s (1896, p. 359) description: “One never recovers from his surprise that there

should be so much life where apparently there is so

little to support it.”

Is Big Sagebrush a Highly

Competitive, Dominating,

Suppressive Species? ___________

Winward (1991, p. 5) answers this question:

Mountain and basin big sagebrush sites in best condition have cover values between 15-20 percent. Those

numerous sites that support cover values in the 30-40

percent category have a much restricted herbaceous

production and are essentially closed to recruitment of

new herbaceous seedlings. Some type of shrub removal

process will be needed before understory forbs and

grasses can regain their natural prominence in these

communities.

He also states that Wyoming big sagebrush stands

with canopy cover over 15 percent would, also, have “a

much restricted herbaceous production.”

During the 1940s and 1950s the range management

community recognized that the canopy cover of big

sagebrush provided a protective barrier for grasses

and forbs from excessive livestock grazing (Pechanec

and Stewart 1949). Big sagebrush forms such an

effective protective cover for grasses and forbs that

Pechanec and Stewart (1944a) estimated that 50 percent of the palatable grasses and forbs under big

sagebrush is unavailable to grazing livestock. This is

illustrated in figure 4.2.

There is an untested hypothesis proposed by some in

the range management community that states: the

surface roots of big sagebrush roots in the interspaces

among big sagebrush plants have the capacity to

capture water and nutrients to the point that they

starve out associated herbaceous plant species. Data

within Tart’s (1996) report refutes this hypothesis (see

table 4.15, chapter IV, and the previous section).

Stands of mountain big sagebrush with the highest

canopy cover at 46 percent had grass and forb cover

above the study averages (Tart 1996, p. 42). Conversely, stands of mountain big sagebrush with the

lowest canopy cover at 17 percent (p. 26) had below

average grass and forb cover. Also, this hypothesis

ignores a number of ecological facts concerning the

interactions of big sagebrush with its associated herbaceous plant species.

This untested hypothesis brings up the question: If

big sagebrush roots are so competitive, why is it that

in grazed-out big sagebrush stands, the only place

grasses and forbs can be found is under the protective

cover of big sagebrush plants (fig. 4.2)? Daddy and

others (1988) found that the greatest root concentration is under the canopy cover of big sagebrush. Why

do the roots of big sagebrush not starve out grasses and

forbs under its canopy?

Four scientific articles show that when grazing is

eliminated or reduced, grass cover increases in spite of

high or increasing big sagebrush canopy cover. McLean

and Tisdale (1972), studying the time it requires for

land to recover from overgrazing, found inside their

West Mara (British Colombia) plot that perennial

grass cover increased from 51 to 67 percent in 9 years

with (probably mountain) big sagebrush canopy cover

of 31 to 34 percent. Outside, big sagebrush canopy

cover was 38 percent, and the cover of perennial grass

increased from 35 to 51 percent. Branson and Miller

(1981) found that after 17 years of improved grazing

management canopy cover of (probably Wyoming) big

sagebrush increased from 23 to 30 percent, and grass

cover increased from 3 to 41 percent. Three other study

sites showed similar trends: below hill top—big sagebrush canopy cover increased from 15.1 to 30.7 percent, perennial grass cover increased from 2.8 to 33.3

percent; big sagebrush-big sagebrush canopy cover

increased from 12.6 to 39.3 percent, perennial grass

cover increased from 1 to 27.9 percent; and sagebrush

strip-big sagebrush canopy cover increased from 31.9

to 36.6 percent, perennial grass cover increased from

10.1 to 36.3 percent. Pearson (1965) found big sagebrush canopy cover inside of an 11-year-old exclosure

to be 34 percent with 39 percent cover of perennial

grasses. Outside his exclosure, canopy cover of big

sagebrush was 11 percent with a perennial grass cover

of 22 percent. Anderson and Holte (1981) reported big

sagebrush canopy cover increased with more than 25

years of protection from grazing from 15 to 23 percent

with perennial grass cover increasing from 0.28 to 5.8

percent. What I found interesting about this study was

that perennial grasses showed any signs of recovery

after starting at a cover value of less than three-tenths

of a percent. Also, of interest is Daddy and others

(1988) citation of the Anderson and Holte (1981) study.

Daddy and others (1988, p. 415) stated: “Anderson and

Holte (1981) reported that canopy cover of big sagebrush increased 54% with little change in cover of

understory grasses after 28 years of complete protection from grazing in southern Idaho.” They expressed

the increase of big sagebrush canopy cover as a percentage, and changed the terms for expressing grass
196 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

cover increase as “little change.” Percentage increase

in grass cover was 2,071 percent (from 0.28 percent to

5.8 percent). These studies showed that as canopy

cover of big sagebrush increased, perennial grass

cover also increased.

Richards and Caldwell (1987) found that big sagebrush has the capacity to draw water from deep, moist

soil layers and at night redistribute water into the

drier upper layers of the soil. Here nonbig sagebrush

plants may parasitize this water (Caldwell and

Richards 1989). They termed this phenomenon hydraulic lift. Caldwell and others (1991) listed the

following advantages for hydraulic lift as prolonging

the activities of fine roots, mycorrhizae, and nutrient

uptake in drying soils. Ryel and others (2002) listed

another advantage, a delay in the development of

xylem embolisms. They estimated that as much as 20

percent of the water used by nonbig sagebrush plants

can come from hydraulic lift on a given day.

A number of studies show that big sagebrush is a soil

builder (Chambers 2001; Charley and West 1975,

1977; Doescher and others 1984; Fairchild and

Brotherson 1980). The nutrient content—such as nitrogen, phosphorus, potassium, calcium, and so forth—

directly under the canopy of big sagebrush is higher

than the nutrient content in the interspaces. For

nitrogen, Charley and West (1975) suggested that

three factors may be operating in concert to account for

the accumulation: first, enhanced fixation by freeliving microorganisms in or under litter; second, animal activity; and third, canopy-capture of wind-transported solids. Mack (1977) describes a fourth factor,

that of absorbing minerals deeper in the soil and

depositing them on the soil surface as litter. As a result

big sagebrush creates islands of fertility that can be

utilized by other plant species. Krannitz and Caldwell

(1995, p. 166) note: “Contrary to expectations, when

roots of any test species contacted, or were in the

vicinity of, Artemisia roots, their growth rate was not

significantly affected.”

Finally, from the allelopathic section (chapter IV),

Daubenmire (1975, p. 31) states: “Field observations

in Washington indicate that not only is there no

allelopathic influence from the species of Artemisia,

but that it has a beneficial effect on other plants.”

Wight and others (1992) describe one of these “beneficial effects on other plants” as water conservation (also

see Chambers 2001) and extending water near the soil

surface by 2 weeks versus interspaces between plants.

They noted that big sagebrush canopies reduce solar

radiation and prolong the period favorable for seedling

establishment for perhaps as long as 28 days (also see

Pierson and Wight 1991 and Chambers 2001 for favorable soil temperatures under big sagebrush).

Recovery of Big Sagebrush After

Fire and Fire Interval _____________

Recovery After Fire

The length of fire interval in the big sagebrush

ecosystem remains an active debate. Mueggler (1976,

p. 6) stated: “Judging from the reports of early explorers, these fires were not frequent enough to alter the

vegetation in favor of more fire-enduring grasses.”

Winward (1991, p. 4) argued for a short interval of 10

to 40 years but acknowledges “...that I perhaps could

not back-up if I were asked for specific figures.”

Winward (1984, p. 3) states: “Normally sagebrush

survives fires through rapid regeneration of seedlings

and in this sense it may be called fire tolerant.”

How rapid can fire-intolerant big sagebrush reestablish itself after a fire? Winward (1984, p. 3) says: “In

most cases it is well on its return to the site 5-10 years

after a burn. Normally enough sagebrush seed remains in the soil surface for rapid recolonization.”

None of 13 mountain and Wyoming big sagebrush

burned sites studied by Wambolt and others (2001)

support Winward’s (1984) statement. Hanson (1929)

noted that grasses were dominant over (probably

mountain) big sagebrush 5 to 10 years after a fire.

Pechanec and Stewart (1944b, p 13) stated the following concerning the recovery of big sagebrush after a

burn: “Eleven years after burning almost no sagebrush has reoccupied the area.” Blaisdell (1950), studying what was probably a mountain big sagebrush

stand, noted some reestablishment 15 years after a

fire. Blaisdell (1953) found little reestablishment of

what was probably a Wyoming big sagebrush stand 12

years after a fire. Harniss and Murray (1973) noted

that full big sagebrush recovery had not occurred even

after 30 years. Bunting and others (1987, p. 4) set

mountain big sagebrush recovery at 15 to 20 years and

observed that “Wyoming big sagebrush will establish

readily from seed if seed is available. Slow growth,

however, reduces the rate at which it recovers compared to other big sagebrush subspecies.” Eichhorn

and Watts (1984, p. 32) reported: “burning removed

big sagebrush (Artemisia tridentata wyomingensis)

from the site and it has not reinvaded after 14 years.”

Wambolt and Payne (1986) reported that 18 years

after a fire, Wyoming big sagebrush canopy cover was

only 16 percent of control and significantly below other

control methods. Fraas and others (1992) found little

recovery of mountain big sagebrush on an 8-year-old

burn. Wambolt and others (1999), studying the production of three subspecies of big sagebrush 19 years

after a fire on the northern Yellowstone winter range,

found that “recoveries of burned compared to unburned
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 197

Wyoming, mountain, and basin big sagebrushes

were...0.1, 1.4 and 11% for production of winter forage, respectively.” They further studied seven other

burn sites of mountain big sagebrush on the northern

Yellowstone winter range and found no significant

recovery of mountain big sagebrush 9 and 13 years

after prescribed burning. West and Yorks (2002, p.

175) noted after 19 years: “Artemisia [Wyoming big

sagebrush] has been slow to reestablish at our burned

locations.” Humphrey (1984), studying the patterns

and mechanisms of plant succession after fire in the

big sagebrush habitat, found a pronounced delay of

some 18 to 32 years in the establishment of big sagebrush. He attributed this delay to big sagebrush dependency on the dispersal of its propagules, achenes,

or seeds. Seed dispersal of big sagebrush as explained

in chapter VI could take some 105 to 211 years to

spread 1 mile (Chambers 2000; Noste and Bushey

1987).

However, Mueggler (1956, p. 1) on probably a Wyoming big sagebrush site noted: “Establishment of

thick stands of big sagebrush (Artemisia tridentata)

seedlings the year following planned burning of sagebrush-grass range sometimes occurs despite all known

precautions.” The key word in his statement is “sometimes.” Unfortunately, workers such as Burhardt and

Tisdale (1976, p. 478) have changed the word “sometime” to “generally,” which gives the misleading impression that most burned big sagebrush stands can

regenerate quickly; or in the case of Winward (1984,

p. 3) most of the time as would be inferred by his

statement that big sagebrush is well on its return 5 to

10 years after a fire.

Somewhat supportive of the Mueggler (1956) study

is the data set I collected from a recent fire near

Provo, UT. In August 1999, a wildfire swept across

the northern half of West Mountain located about 7 miles

southwest of Provo. The fire killed all big sagebrush

plants in its path. The big sagebrush population on the

study site seemed to be a mixture of mountain big

sagebrush and a Wyoming big sagebrush introgressed

by mountain big sagebrush (McArthur and Sanderson,

personal communication). Prior to the fire, summer

1997, I established two line intercepts to determine

big sagebrush canopy cover. The area where these two

line intercepts had been established were burned.

GPS coordinates (elevation 5,000 feet in a 14 to 16

inch precipitation zone) for the start of the first line

intercept was N 40° 07.357; W 111° 48.997 and went

1,500 feet due west. The intercept was divided into

five 300 foot sections. Canopy cover of big sagebrush

was 31.6 ± 4.45 percent. In spring of 2004, canopy

cover was 0 percent. During the spring 2004, I established six 1-acre plots along the intercept and counted

the number of big sagebrush plants growing within

the boundaries of each plot. The 1-acre plots were

established south and north of the intercept for a total

of eight plots. The closest seed source for big sagebrush

was 0.4 mile away; therefore, all big sagebrush plants

counted in the 1 acre plots were from residual seed

surviving the fire. Production of seed stalks were

noted 5 years after the fire in autumn 2004. Results on

a per plot bases were: 0, 0, 0, 2, 3, 14, 21, 47 big

sagebrush seedlings.

GPS coordinates (elevation 6,000 feet in a 14 to 16

inch precipitation zone) from the start of the second

line intercept was N 40° 06.815; W 111° 49.214 and

went 900 feet due south. Canopy cover of big sagebrush

was 32.4 ± 4.9 percent. In spring 2004, canopy cover

was 0.05 percent. Five 1-acre plots were established

along the intercept as described above. Results on a

per plots bases were 1, 1, 3, 11, 121 seedlings.

The above data set suggests that in some cases big

sagebrush can give the appearance of being well on its

return 5 to 10 years after a fire but in most cases it is

not. All this on the same fire. I define, some cases or

sometimes, as being an event that occurs with a

frequency of 20 percent or less. Plots that would give

appearance of rapid recovery of big sagebrush after

the 1999 West Mountain Fire contained 47 and 121, 4-

year-old big sagebrush plants derived from residual

seeds surviving the fire, or 15.4 percent of the plots

showing signs of a possible rapid recovery. I intrepret

this data set not to support Winward’s (1984, p. 3)

statement: “In most cases...”

In addition to the scientific articles previously cited,

I have measured the reestablishment of mountain big

sagebrush on an approximately 360 acre, 14-year-old

burn known as the Grandine Fire located some 3 miles

northeast of Stone, ID (Klott and Ketchum 1991). I

established a point at N 42° 01.545'; W 112° 38.283';

300 feet from the western edge of the Grandine Fire

and constructed a line running due east into the

burned area for 3,300 feet (the line could have been

continued for an additional 3,000 feet or more) and

used this line to determine percent canopy cover of

mountain big sagebrush and sprouting shrubs such as

rabbitbrush (Chryothamnus ssp.), snakeweed

(Gutierrezia ssp.), and horsebrush (Tetradymia spp.).

Mountain big sagebrush canopy cover for the unburned area—the first 300 feet—was 30 percent and 4

percent for the sprouting shrubs. For the first 300 feet

into the burned area, mountain big sagebrush canopy

cover was 3 percent and 2 percent for the sprouting

shrubs. Three percent mountain big sagebrush canopy

cover continued to 600 feet and from 600 feet to the

3,300-foot point; that is, for 2,400 feet my line did not

intercept a single big sagebrush plant. Sprouting shrubs

canopy cover varied over the same distance from 8 to

26 percent. The rate of mountain big sagebrush reestablishment on this burn from the west to the east was

about 42 feet per year. Reestablishment from the east
198 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

to the west and from the north to the south was

essentially nil, and the reestablishment rate from the

south to the north was half of that of the west to the

east. Based on these measurements, recovery of big

sagebrush on the burn would take some 71 years just

to reach the 3,300-foot point and would not include

the time needed for full canopy recover. There were

widely scattered mountain big sagebrush plants

throughout most of the burn site that would help to

reduce the 71-year recovery rate, but they too are

subject to 42 feet per year spread in an easterly

direction and even shorter distance in a northerly

direction. These scattered plants were probably derived from soil-borne seeds that survived the burn.

Fire Interval

In an often-cited article by Winward (1991, p. 4), he,

in reference to the big sagebrush ecosystem, states:

“These ecosystems, which have developed with an

historical 10-40 year fire interval, were dependent on

this periodic removal or thinning of sagebrush crowns

to maintain their balanced understories.” However, a

31-year study of a mature big sagebrush stand in the

Gravelly Mountains in Montana demonstrated the

ability of a big sagebrush ecosystem to maintain itself

without the occurrence of fire (Lommasson 1948).

Others estimate a much longer fire interval.

Houston (1973) estimated the fire interval in what

he termed “bunchgrass steppes” of northern

Yellowstone National Park winter range to be from 53

to 96 years. Feeling that modern humans have influenced the fire interval through fire suppression activities, he adjusted the interval by subtracting 80 years

from the ages of living trees and came up with adjusted

fire intervals of 32 to 70 years in the big sagebrush

steppes of northern Yellowstone National Park. I

believe that Houston (1973) was overly optimistic in

his estimate on how soon modern humans could significantly suppress fires. This ability may not have

occurred until the 1950s (see “Fire Statistics-Average

number of fires and acres burned by decade” on http:/

/www.nifc.gov/stats/wildlandfirestats.html-Wildland).

Even Houston’s (1973) adjusted fire interval of 32 to 70

years exceeds the interval suggested by Winward

(1991). Wright and Bailey (1982, p.159) suggested fire

interval of 50 years “based on the vigorous response of

horsebrush (Tetradymia canescens) to fire and the 30-

plus years that are needed for it to decline to a low level

after a fire in eastern Idaho.” They further observed (p.

160): “If fires occurred every 20 to 25 years, as Houston

[1973] implies, many sagebrush-grass communities in

eastern Idaho could be dominated by horsebrush and

rabbitbrush (Chrysothamnus ssp.).” (Also see Young

and Evans 1978b and Britton 1979.) For Wyoming big

sagebrush ecosystems, Wright and Bailey (1982) suggested a fire interval as long as 100 years. Whisenant

(1990, p. 4) stated: “Prior to the arrival of white

settlers, fire intervals in the sagebrush (Artemisia)-

steppe probably varied between 60 and 110 years,”

and that due to the presence of cheatgrass (Bromus

tectorum), on what was big sagebrush steppe, these

areas can burn at intervals of less than 5 years,

resulting in a total loss of big sagebrush.

Winward (1984) suggests that mountain big sagebrush, which usually grows at higher elevations, has

a burn cycle of 20 to 30 years. This is based on higher

vegetative productivity of the mountain big sagebrush

sites, or in other words, higher fine fuel accumulation

and higher frequency of lightning strikes, which he

believes results in a shorter fire cycle as compared to

basin and Wyoming big sagebrush sites that produce

less fine fuels and experience fewer lightning strikes.

However, I believe that the greater accumulation of

biomass and higher number of lightning strikes on

mountain big sagebrush sites could be offset somewhat by lower temperatures and higher humidity that

occur on these sites.

Arno and Gruell (1983) found that the fire interval

prior to 1910, at ecotones between mountain big sagebrush ecosystems and forest ecosystems, ranged from

35 to 40 years (also see Gruell 1983). Miller and Rose

(1999) suggest a fire interval of 12 to 15 years based on

fire scars found on ponderosa pine (Pinus ponderosa).

Neither Arno and Gruell (1983) nor Miller and Rose

(1999) have linked fire scarring of trees to fire interval

in mountain big sagebrush communities. On the ridge

just west of Brown Lake in the Great Basin National

Park, I have found basal fire scarring of limber pine (P.

flexilis) and Engelmann spruce (Picea engelmannii)

growing on talus that is not capable of carrying ground

fires. These scars were caused by lighting strikes.

Perhaps fire scarring due to ground fires can be identified from scars due to lighting strikes.

Soil characteristics of the ponderosa pine clusters

used in the Miller and Rose (1999) study may be

dramatically different from those of the adjacent mountain big sagebrush stands (Billings 1950; Delucia and

others 1989; Gallardo and Schlesinger 1996;

Schlesinger and others 1989). If so, what effects these

differences might have on fire intervals on either plant

community were not addressed. Also, Miller and Rose’s

(1999) sampling method was not done in a randomized

manner; they chose only trees bearing fire scars. In

fact, they (Miller and Rose 1999, p. 553) stated: “In

clusters I and IV, trees with the maximum number of

fire scars visible on the surface were selected for

sampling.” Would this tend to overestimate number of

fires for a given period? Baker and Ehle (2001, p. 1205)

state: “Inadequate sampling and targeting multiplescarred trees and high scarred densities bias mean FI
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 199

toward shorter intervals.” They suggest mean fire

interval for ponderosa pine may be 22 to 308 years.

The Miller and Rose (1999) report does present data

that show a major fire event occurring at a 50-year or

more cycle. These major fire events could have burned

over a significant amount of mountain big sagebrush

area. A fire interval of greater than 50 years is probably compatible with maintaining a mountain big

sagebrush community (Lommasson 1948).

There are 10 biological and ecological characteristics of mountain or any other big sagebrush that do not

support the idea that this big sagebrush evolved in an

environment of frequent fires: (1) a life expectancy of

70+ years (Daubenmire 1975; Ferguson 1964; Fowler

and Helvey 1974; Passey and Hugie 1963); (2) highly

flammable bark (the stringy bark makes excellent fire

starting material); (3) production of highly flammable

essential oils (Buttkus and Bose 1977; Cedarleaf and

others 1983; Charlwood and Charlwood 1991; Kelsey

1986; Kinney and others 1941; Powell 1970); (4) a

low-growth form that is susceptible to crown fires

(Beetle 1960; McArthur and others 1979); (5)

nonsprouting (Peterson 1995; West and Hassan 1985;

Wright and others 1979); (6) seed dispersal occurs in

late fall or early winter long after the fire season has

ended (Beetle 1960; Young and Evans 1989); (7) lack

of a strong seed bank in the soil (Beetle 1960; Meyer

1990, 1994; Young and Evans 1989), although sometimes big sagebrush can express a strong seed bank

(Mueggler 1956); (8) seed has no anatomical fire resistance structures or adaptations, that is, it has no thick

seed coat (Diettert 1938); (9) seeds must lie on the soil

surface, which exposes them to higher temperatures

than seeds that are deeper in the soil (Hassan and

West 1986; Jacobson and Welch 1987); and (10) seeds

lack any adaptations for long-distance dispersal, hence,

mountain big sagebrush lack the ability for rapid

reestablishment (Astroth and Frischnecht 1984; Chambers 2000; Frischknecht 1979; Johnson and Payne

1968; Walton and others 1986; Wambolt and others

1989; Young and Evans 1989).

Effects of Fire on the Big Sagebrush

Ecosystem _____________________

Effect of Fire on Soil Chemistry

The effects of fire on soil-surface (0 to 5 cm) chemistry have been studied by a number of workers (Acker

1992; Blank and others 1994a, 1995; Britton and

Ralphs 1979; Daubenmire 1968; Hobbs and Schimel

1984; Mueggler 1976; Nimir and Payne 1978; Young

1983b). In general, these effects on burned sites are

increases in the amounts of phosphorus, potassium,

calcium, magnesium, micronutrients, and an increase

in soil pH, and decreases in the amounts of sulfur and

total nitrogen. It seems after a fire that nitrogen lost

through volatilization is more than replaced by an

increased output of nitrifying bacteria and increased

nitrogen mineralization; thus, more nitrogen is available to the plants for at least a couple of years after the

fire. Part of this increase in nitrogen comes from the

green manure effect of dead big sagebrush and other

species roots mentioned earlier by Daubenmire (1970).

Acker (1992) detected no change in soil organic matter

as a result of fire, but his sampling depth of 10 cm may

have been too deep to measure changes that may have

occurred at the surface. Blank and others (1995),

however, found organic carbon to be significantly

lower on soil surfaces of burned sites than unburned

sites. They further found the following soil surface

attributes to be significantly lower on burned sites:

cation exchange capacity, cooper, zinc, and nitrate

nitrogen. Attributes that were significantly higher on

burned sites were: iron, sulfate, acetate, formate, and

water drop penetration time or wettability of the soil.

Water Repellency

Water repellency induced by the burning of big

sagebrush litter was studied by Salih and others

(1973). They found that water repellency did not occur

until temperatures reached about 704 to 760 °C, and

above 982 °C there was no repellency at all. Blank and

others (1995) also described a decrease in moisture

infiltration due to water-induced repellecy as a result

of burning big sagebrush. Water repellency can also be

induced by burning litter of plant species other than

big sagebrush (DeByle 1973; de Jonge and others

1999; Everett and others 1995; Robichaud and

Hungerford 2000). Blank and others (1994b, p. 220)

noted in their study concerned with the production of

the organic acid from four different soil litters (big

sagebrush, squirreltail [Elymnus hystrix], cheatgrass,

and medusahead [Taeniatherum caputmedusae ssp.

Asperum]): “The lack of variation in levels of certain

organic acids among the soil-litters, however, suggest

they were synthesized via pyrolysis of the soil humic

fraction, rather than originating from the plant litter

itself.”

Other Fire Effects

In addition, fires can change the soil fabric of seedbeds in the following five ways: (1) caused the compaction of mineral grains through loss of organic detritus,

(2) carbonized plant litter to a depth of approximately

5 cm, (3) caused the loss of fluoresecent compounds in

sagebrush litter, (4) coated mineral particles with

organic compounds, and (5) cleaved micaceous minerals (Blank and others 1995). Wicklow-Howard (1989)

presents data suggesting that vesicular-arbuscular

mycorrhizae fungi require 2 years to recover from the
200 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

effects of fire. The overall effects of these changes on

plant reestablishment on burned sites are not fully

understood.

Islands of fertility occur under the canopy of big

sagebrush plants (see chapter IV for details). According to work done by Halvorson and others (1997), these

islands are detectable 9 years after a fire. In general,

their unburned sites were significantly higher in most

of the soil variables measured, and differences were

greatest near the location of a big sagebrush plant or

charred stump. They further noted (p. 287): “In contrast, burned soil was not distinguishable from unburned soil at distances greater than 50 cm away from

a live A. tridentata axis or a charred stump indicating

that soil patterns were most affected by removal of the

plant and not by the fire.” Soil factors that showed

significantly higher levels, 9 years after a fire, closer to

charred stumps, were: total organic carbon, total nitrogen, water soluble carbon, electrical conductivity,

and soil microbial biomass carbon. Therefore, it is

apparent that big sagebrush plants build soil fertility

while alive, and these islands of fertility remain for

years after their death.

There is some evidence that, for a few years after a

fire, crude protein levels of grasses and forbs are

higher on burned sites than unburned sites (Bunting

1989; Cook and others 1994; Hobbs and Spowart

1984). It should be noted, however, that any increases

in crude protein levels are generally negated by late

summer and fall when green foliage becomes desiccated and dormant (Peterson 1995).

Removing Big Sagebrush ________

Big sagebrush can be killed or thinned by a variety

of techniques that can be classified into three basic

categories: prescribed burning, chemical, and mechanical (Alley 1965; Pechanec and others 1954, 1965;

Vallentine 1989). An additional method involves flooding (Ganskopp 1986; Pechanec and others 1954;

Vallentine 1989).

Prescribed Burning

Guidelines for burning of big sagebrush have been

published by Bunting and others (1987) and cover

season of the year, size of fire, rest and deferment,

prescription development, and safety.

Season of the Year—Cool season grasses such as

bluebunch wheatgrass (Agropyron spicatum) are damaged the least by fall burns, and warm season grasses

such as blue grama (Bouteloua gracilis) are damaged

the least by spring burns. In the northern portion of

the big sagebrush range no warm season grasses are

present, thus eliminating the conflict between spring

and fall burning. Bunting and others (1987, p. 9)

stated: “In our experience, the perennial herbaceous

species are most resistant if they are burned when

completely dormant. In much of the Great Basin,

spring fires are frequently not feasible due to the

abundant moisture in late winter and spring.” Late

winter burning may often be feasible in eastern Idaho

and western Montana. Caution should be taken when

there has been sufficient late summer or early fall

precipitation to cause fall green-up, because under

these conditions, fire mortality of grasses can be much

higher than burning during periods of complete

dormancy.

Fall burning is the most common time to burn in the

northern Great Basin, but due to possible fall greenup, managers also consider late summer burning when

perennial grasses are dormant. This maximizes the

number of burning days, and the drier conditions

allow the carrying of fire with lower fuel loads and

larger fire size. Also, due to drier conditions, late

summer fires have a greater risk of fire escape. Spring

burnings, due to high moisture and compacted fuels,

are usually smaller and leave more unburned patches.

Neuenschwander (1980) describes a method for burning in the winter that requires no fire control or mopup

and burns only small patches.

Size of Fire—Bunting and others (1987, p. 15)

point out: “Consideration should also be given to the

amount of area that can be burned in a single burning

period (normally 4 to 6 hours). In continuous fuels this

limits the maximum size to about 500 to 2,000 acres

when hand firing, and 1,000 to 3,500 acres when aerial

ignition is used. Of course, where natural fire breaks

do not occur, fire lines will have to be constructed to

restrict fires to the desired size.”

Rest and Deferment—The common plan for burning a given site is to rest the site from grazing to allow

the buildup of fine fuels that are needed (600 to 700

pounds per acre) (Wright and others 1979) to carry the

fire through the big sagebrush stand, or in other

words, no pretreatment is needed to reduce big sagebrush canopy cover to increase grass yields to the point

that grass would be able to carry a fire. After the burn,

rest is recommended for at least 1 year and preferably

2 years.

Prescription Development—Bunting and others

(1987) list weather factors for a prescribed big sagebrush burn: (1) relative humidity 15 to 35 percent; (2)

temperature 60 to 85 °F; and (3) midflame wind 4 to15

miles per hour. Of these three factors, the most important is windspeed, which influences flame lengths and

rate of spread. Bunting and others (1987, p. 16) noted:

“When the relative humidity is greater than 30 percent, the temperature is less than 60 °F, and the

midflame windspeed is less than 4 mi/h, it is unlikely

that fire will spread satisfactorily unless fine fuels
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 201

exceed 600 lb/acre.” They further observed (p. 16):

“When the relative humidity is less than 15 percent

and the temperature is greater than 85 °F, fire control

becomes more difficult. Windspeeds greater than 15

mi/h not only create fire control problems but also limit

the effectiveness of fire within the burn area. At high

windspeeds, the lateral spread of the fire is limited,

and long narrow stringers of burned areas result.”

Slope does influence the rate of spread. A 30 percent

slope will increase the rate of spread of a fire by a factor

of two to three times over the same conditions on level

ground, and 50 percent slope by a factor of four to seven

times. Slopes increase the effective reach of a fire and

lower the need of fuel loads and windspeed.

Safety—Bunting and others (1987, p. 17) warn:

“Burning under hotter and drier conditions increases

the risk of escape and the need for suppression forces.”

The fire crew needs to be briefed as to the overall plan

and each individual’s assignment. Personnel in charge

of holding firelines need to be aware of critical points

along the fire perimeter. The contingency plan in case

of fire escape must be outlined. Location of water

sources should be identified for all engine operators.

Finally, escape routes for all personnel must be clearly

identified.

Other factors that need to be discussed include:

communication, what to do in case of changing weather

conditions, and self-generating fire winds. Publications concerning fire behavior and modeling in big

sagebrush ecosystems are available (Brown 1982;

Frandsen 1983; Sapsis and Kauffman 1991).

Chemical Control

The literature on chemical control of big sagebrush

is voluminous, as will be seen in this section.

Nine chemicals have been used to kill big sagebrush:

• 2,4-D [(2, 4-dichlorophenoxy) acetic acid]

• 2,4,5-T [(2,4,5-trichlorophenoxy) acetic acid]

• dicamba (2-methoxy-3,6-dichlorobenozic acid)

• tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3, 4

thiadiazol-2-yl]-N, N’-dimethylurea)

• clopyralid (3, 6-dichloro-2-pyridinecarboxylic acid

monoethanolamine salt)

• picloram (4-amino-3,5,6-trichloropicolinic acid)

• karbutilate [tert-butylcarbamic acid ester with

3(m-hyroxyphenyl)-1, 1-dimethylurea]

• metsulfuron [2-[[[[(4-methoxy-6- methyl-1,3,5-

triazin-2yl) amino]carbonyl]amino]sulfonyl] benzoic acid]

• fluroxypyr

(Baxter 1996; Cornelius and Graham 1951; Evans and

others 1983; Pechanec and others 1954; Whisenant

1986; Whitson and Nix 1989; Young and Evans 1978a).

The first three are synthetic auxins (Hopkins 1999)

and are more resistant to oxidative enzymes than

natural auxins. At low concentration they behave like

auxins, that is, control or regulate plant cell growth

and stem elongation, and can be used to enhance

rooting of cuttings, development of seedless fruit,

setting of fruit, and so forth. But at higher concentrations they kill broadleaf plants without harming grasses

and other nonbroadleaf plants (Hamner and Tukey

1944; Hopkins 1999; Young 1983a). The herbicide

2,4,5-T has been banned by many jurisdictions because of high concentrations of dioxin, a highly carcinogenic substance; therefore, I will not discuss its uses

any further in this publication (Hopkins 1999).

2,4-D is perhaps the most widely used herbicide for

the control of big sagebrush. Its use as an herbicide

was first proposed in 1941 in the form of a personnel

communication by Kraus, as referenced by Hamner

and Tukey (1944). The first successful uses of 2,4-D to

kill big sagebrush were reported by Cornelius and

Graham (1951) and Hull and Vaughn (1951). This

started an avalanche of reports and studies that continued into the mid-1980s.

2,4-D can be manufactured as three esters: butyl,

isopropyl, and ethyl (Hyder and others 1958a). Hyder

and others (1958a) tested the different formulations

and concluded that the isopropyl form was not as

effective against big sagebrush as the butyl and ethyl

esters. They suggested that 1.5 ai (active ingredient)

pounds per acre emulsified in water would kill in

excess of 75 percent of the big sagebrush plants. Alley

and Bohmont (1958) recommended 2 ai pounds per

acre of butyl ester mixed in oil. Cook (1963, p. 194),

studying the effectiveness of a mixture of equal parts

isopropyl and butyl esters of 2,4-D in water at 1.5, 2.0,

and 3.0 ai pounds per acre applied on three dates

(about May 15, May 30, and June 15), found that

“when growing conditions were favorable, all three

rates gave satisfactory results; when growing conditions were unfavorable none of the rates gave satisfactory control.” Cook (1963) showed that the two May

dates were usually more effective in killing big sagebrush than the June date in work performed in Utah.

The difference between satisfactory and unsatisfactory results seems to lie with temperatures and percentage of soil moisture—maximum temperatures

above 70 °F and minimum temperatures above 40 °F

with soil moisture above 12 percent on the day of

treatment, or in others words, during periods of favorable growing conditions. For California, Cornelius and

Graham (1958) found best control of big sagebrush

occurred using butyl ester of 2,4-D at a rate of 2 ai

pounds per acre during active big sagebrush growth

that usually occurs from late May to mid-June. Hyder

(1953, 1954), Hyder and others (1956, 1962), and Hyder

and Sneva (1955) reported similar results in Oregon.

Cornelius and Graham (1958) further noted that the

spray must be distributed to all the leaves of a plant

for a total kill. Hormay and others (1962, p. 326)
202 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

confirmed the effective distribution: “More often than

not the unsprayed portion continued to live, indicating

the chemical was not translocated in amounts enough

to affect growth of the unsprayed portion.”

Bartolome and Heady (1978), studying the rate of

big sagebrush establishment after plowing and spraying with 2,4-D, found that “reinvasion begins immediately after treatment.” Unlike a burn in which fire

kills all big sagebrush plants in its path (Cluff and

others 1983), spraying big sagebrush with 2,4-D kills

some plants totally, others partly, and a few are totally

missed, all at random. These partial killed and total

escaped plants can recover quickly and become a seed

source, which results in a quicker recovery of big

sagebrush under these kinds of treatment than with

fire.

This point is illustrated by Wambolt and Payne

(1986) who compared four methods of Wyoming big

sagebrush control. Wyoming big sagebrush recovered

faster from plowing, rotocutting, and spraying with

2,4-D than when burned. Weldon and others (1958, p.

303) noted: “Rangeland on which 75 per cent or more

of the sagebrush has been chemically controlled may

be expected to remain relatively free from sagebrush

seedlings for at least a 4-year period after chemical

treatments.” Gardner (1961) estimated the life of 2, 4-

D spraying projects to be about 12 years, Johnson

(1969) estimated less than 14 years, and Thilenius and

Brown (1974) estimated 3 to 4 years. Thilenius and

Brown (1974, p. 224) observed: “On three summer

cattle ranges in the Bighorn, increased herbage production after sagebrush control with 2, 4-D was a

relatively short-lived phenomenon. Declines in production and in the proportion of graminoids in the

herbage did not appear to be related to reinvasion of

sagebrush as this was minimal on all three sites even

after 10 to 11 years.”

In additional to killing big sagebrush when spraying

with 2,4-D, this method can and does kill other broadleaf plants such as forbs, thus reducing the productivity of these valuable plants (Anderson 1969a;

Blaisdell and Mueggler 1956; Miller and others 1980;

Schumaker and Hanson 1977; Tabler 1968; Wilbert

1963). As a result of reduced biomass production of

shrubs and forbs on 2,4-D sprayed big sagebrush

ecosystems, a reduction also occurs in total biomass

production of the treated site (Schumaker and Hanson

1977; Sturges 1986, 1994; Tabler 1968).

Often after spraying big sagebrush ecosystems with

2,4-D, grass production is increased two or threefold or

more when compared to unsprayed areas (Alley 1956;

Cornelius and Graham 1951; Hull and others 1952;

McDaniel and others 1991; Miller and others1980;

Sturges 1986, 1994; Tabler 1968; Wilbert 1963). Some

of the workers seemed to be comparing treated sites

with untreated sites, the latter appearing, in their

photos, to be heavily overgrazed. This issue was discussed earlier (Evans and Young 1975; Hedrick and

others 1966; Hull and others 1952; Hyder and Sneva

1956; Johnson 1969) (tables 7.1 and 7.2). Hull and

Klomp (1974) noted in their study that to obtain the

two- or threefold increase in grass production that

nearly 100 percent of the big sagebrush needed to be

killed, which would be devastating to the obligates of

big sagebrush and would result in an overwhelming

reduction in the biodiversity of the treated sites (Welch

2002; Welch and Criddle 2003; see chapters II and III

for more details).

The effects of spraying mountain big sagebrush sites

with 2,4-D on soils have been studied by Burke and

others (1987, p. 1337), whose results or conclusions are

somewhat confusing in that they claim that “Essentially, control of big sagebrush, in the absence of

grazing, has no effect on site fertility.” This conflicts

with their earlier statement (p. 1337) that “undershrub net N mineralization rates were higher under

shrubs in the sagebrush vegetation than under former

shrubs in the grass vegetation,” and that in the grass

vegetation, N mineralization rates were similar under

former shrub sites versus former interspace sites

among shrubs. Nitrogen is the most limiting of all the

plant mineral nutrients in arid and semiarid soils;

therefore, decreases in nitrogen mineralization due to

the loss of big sagebrush would greatly affect soil

fertility.

Tebuthiuron is a nonselective herbicide that is surface broadcast onto soil where it moves with water into

the rooting zone of plants and is absorbed by plant

roots. Once absorbed, tebuthiuron is translocated to

stems and leaves where it inhibits photosynthesis.

Klauzer and Arnold (1975) were among the first to

demonstrate the ability of tebuthiuron to kill big

sagebrush on native wildlands. Due to its nonselective

properties, tebuthiuron not only reduced the productivity of big sagebrush but also herbaceous productivity at all application rates—0.22 to 3.57 ai pounds per

acre (Britton and Sneva (1981, 1983). Clary and others

(1985), working in a mountain big sagebrush site,

found no significant increases in grass or forb production 3 years after using tebuthiuron at the rates of 0.53

to 2.41 ai pounds per acre, even though big sagebrush

production was dramatically reduced. Whitson and

Alley (1984) reported similar results. Marion and

others (1986, p. 123) also reported satisfactory control

of big sagebrush using tebuthiuron at levels from 0.25

to 1.50 ai pounds per acre and observed: “Sandberg

bluegrass reduction due to the herbicide was not

significant at any rate tested.” Whitson and others

(1988) reported, 7 years after treatment with

tebuthiuron (0.27 to 0.98 ai pounds per acre), a significant increase of cheatgrass on one site and a significant increase of western wheatgrass on the other site.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005 203

Not all perennial grasses showed an increase. Murray

(1988) reported no significant increase in grass production 2 and 3 years after treating a mountain big

sagebrush site with tebuthiuron (0.11 to 0.35 ai pounds

per acre) but found a significant increase in grass

production the fourth year. Forb production was unaffected by the treatment, while big sagebrush production was greatly reduced at all levels of tebuthiuron

and for all 3 years. Wachocki and others (2001) reported no significant increase in understory vegetation due to treating mountain big sagebrush sites with

tebuthiuron. McDaniel and others (1992), however,

reported significant increases in understory vegetation due to treating primary Wyoming big sagebrush

sites with tebuthiuron. They found a few big sagebrush seedlings 8 to 10 years after tebuthiuron treatments were applied, suggesting a long big sagebrush

recovery period.

Tebuthiuron appears to be an effective herbicide

against big sagebrush, but because of its nonselective

characteristic it may harm nontarget plants such as

grasses and forbs.

Other chemicals that can control big sagebrush but

have received limited study are dicamba, clopyralid,

picloram, karbutilate, metsulfuron, and fluroxypyr

(McDaniel and others 1991; Whisenant 1986, 1987;

Whitson and Nix 1989; Young and Evans 1978a).

More information on this topic can be found in the

literature listed in table 7.3.

Mechanical Control

Mechanical control techniques involve uprooting,

shredding of aerial parts, crushing, or trampling of big

sagebrush plants that result in the death of a high

percentage of the plants. Names of mechanical control

techniques reflect the type of equipment used: plowing/disking, disk-chaining, root plowing, anchor chaining, railing, harrowing, and rotobeating (Davis 1983;

Parker 1979; Pechanec and others 1954, 1965; Plummer

and others 1968; Sampson and Schultz 1957; Vallentine

1989). The first three techniques not only destroy big

sagebrush but also the herbaceous vegetation to such

a degree that seeding after treatment is required. Any

control method conducted near or after big sagebrush

seed have matured (mid-October and on) will help to

speed up the recovery of big sagebrush and reduce the

amount of big sagebrush seeds needed to seed after

treatment (Bleak and Miller 1955; Johnson and Payne

1968).

Plowing/Disking—Several kinds of equipment are

used in this method of big sagebrush control: standard

disk, wheatland diskplow, brushland diskplow, and

the offset disk. The standard disk and wheatland

diskplow are too light to hold up under the rigors of

wildland tillage. The brushland plow and heavier

versions of the offset disk are built strong enough to

avoid excessive breakage (Vallentine 1989). The brushland diskplow is a heavy duty plow where each disk

pair is connected by a common shaft and bearing

assembly to a single spring-loaded arm, which allows

a given pair of disks to ride over obstructions, such as

rocks, or to move down into small holes without

interfering with the workings of other disk sets. Plowing near or after big sagebrush seed have matured

(mid-October) will help to speed the recovery of big

sagebrush and reduce the amount of big sagebrush

seeds needed to seed after treatment. Sprouting shrubs

are not killed by brushland plowing.

Disk-Chain—The disk-chain represents the combination of two pieces of equipment: an anchor chain

and a disk. It was developed in Australia during the

early 1960s by welding large disks 22 inches in diameter and 0.75 inch thick to alternate links of an anchor

chain about 100 feet long that was pulled diagonally by

two crawler tractors. This implement works like a disk

plow but with the flexibility and lower cost of an

anchor chain. In addition to the diagonal pulling

configuration, a triangular configuration has been

developed that is pulled by a single crawler tractor.

The base of the triangle is a flexible, packer-rolling

brace attached to the two trailing ends of the disk

chains. The packer-rolling brace aids in seedbed preparation by firming the treated soil. Broadcast seeders

can be attached above the implement or the treated

area can be seeded aerially. The disk chain is ineffective against sprouting shrubs.

Root Plow—This implement is constructed by attaching a wedge shaped blade to two sturdy upright

shanks usually mounted behind a crawler tractor.

Riser fins are welded on top of the blade to aid in

cutting rhizomes and heaving roots and crowns toward the surface of the soil. The root plow is not useful

in rocky or uneven soil.

Table 7.3—Literature not cited in text on controlling big sagebrush with herbicides.

Anderson 1969b

Hyder and Sneva 1962

Hyder and others 1958b

Johnson and others 1980

Johnson 1964

Johnson 1958

Kay and Street 1961

Kituku and others 1993

Lord and Sanderson 1962

Mangan and Autenrieth 1985

Robertson and Cords 1956

Schroeder and Sturges 1980

Sneva and Hyder 1966
204 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-144. 2005

Anchor Chain—The anchor chain is probably the

most used implement for the control of big sagebrush.

It consists of an anchor chain usually 200 to 500 feet

long dragged in a U-shape behind two crawler tractors

traveling parallel to each other. Vallentine (1989)

recommended a chain length to swath width ratio of

2:1 to 3:1. For a 300-foot chain, the swath width should

be from 100 to 175 feet for effective control of big

sagebrush. Also, higher speeds give a higher kill rate.

The weight of chain links varies from 40 to 90 pounds.

Heavier chains kill greater numbers of big sagebrush

plants but also cause greater damage to nontarget

plant species. The anchor chain is ineffective against

sprouting shrubs. Plummer and others (1968, p. 25)

noted: “Chaining efficiently thins and opens dense

stands of big sagebrush, and it covers seed well. This

allows establishment of perennial herbs or permits

development of suppressed understory herbs, yet

retains sufficient big sagebrush for use as a satisfactory browse component.” Chaining allows litter to

remain on the soil surface, thus providing a protective

layer for both soil and seedlings.

Railer—A railer is constructed of a heavy railroad

rail, H-beam, or channel iron attached to a rigid Aframe with the apex being the pulling point. The rail

is dragged over the big sagebrush resulting in uprooting and breaking off mature big sagebrush plants with

little adverse effect on most grasses and forbs and

young big sagebrush plants. The railer is ineffective

against sprouting shrubs.

Pipe Harrow—A pipe harrow is built by welding

spikes in a spiral pattern to a 4-inch steel pipe. Several

such pipes are attached to a spreader bar by means of

individual swivels, which allow the pipe to rotate as

debris comes in contact with the harrow. It is then selfcleaning and usable on rocky sites. It is effective in

thinning big sagebrush stands but does some damage

to perennial grasses and forbs. Enough soil is disturbed to effectively cover broadcast seeds. This implement is ineffective against sprouting shrubs.

Rotobeater—Rotobeaters are simply heavy duty

rotary mowers with single or double blades. They are

effective on mature big sagebrush plants but ineffective on seedlings and young plants under 12 inches

high and on sprouting shrubs. Perennial grasses and

forbs are not damaged when rotobeaters are properly

adjusted to cut about 3 inches above the soil surface.

Combining Burning and Mechanical

Control Techniques

On the Curlew National Grasslands a combination

of techniques is used to control bulbous bluegrass (Poa

bulbosa) and mountain big sagebrush. These techniques consist of fall burning and deep plowing, summer fallowing (disking), fall planting of dry land wheat,

harvesting, and then planting exotic forbs and grasses

with a rangeland drill.

In May 2001 I visited one such treatment site (800+

acres) called the North Hess-Haws field, 9 years after

treatment. Here a 1,500-foot line intercept vegetive

analysis was conducted to determine the cover of

bulbous bluegrass. The line started at N 42° 12.887'; W

112° 34.929 in the southern half of the field and went

west. Cover of bulbous bluegrass ranged on a per 100-

foot basis from 10 to 48 percent for an overall cover of

22 percent. Bulbous bluegrass cover in the north half

of the field appeared to be doubled that of the 1,500-

foot line intercept of the south half. So controlling

bulbous blue grass appears to be questionable at best.

But control of mountain big sagebrush was extremely effective; that is, the number of mountain big

sagebrush plants on the 800+ acres of treated land was

nearly zero. However, there were a few small sites

(islands) that escaped treatment. The young mountain big sagebrush plant that had established itself

the farthest into the treated area was 217 feet east of

a stand of mountain big sagebrush. Meaning that in 9

years mountain big sagebrush was advancing at a

maximum rate of 24 feet per year, or in other words, it

would take mountain big sagebrush about 220 years to

reoccupy the 1-mile-wide treated site.

One effect of this type of control method is a reduction in the number of birds and in the number of

species of birds that used the treated area as compared

to nontreated big sagebrush (Welch 2002). I conducted

a 1-mile-long bird census in the treated area and in the

adjacent big sagebrush stand (east of treated site; see

Welch 2002 for study details and for information on

other areas). The starting point for the treated site

was: N 42° 12.709'; W 112° 35.066' and went north

(Welch 2002, transect 5, Idaho, Holbrook). A total of 10

birds of three species were spotted (Welch 2002). The

starting point for the big sagebrush stand was: N 42°

13.510'; W 112° 34.795' and went south (Welch 2002,

transect 6). A total of 44 birds of 11 species were

spotted (Welch 2002).

More information concerning the various methods

to control big sagebrush can be found in Vallentine

(1989).

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