United States

Department of

Agriculture

Forest Service

Grazing on Regeneration Sites

Encourages Pine Seedling Growth

Pacific Southwest

Research Station

Research Paper

PSW-RP-223

Raymond D. Ratliff Renee G. Denton
Abstract

Ratliff, Raymond D.; Denton, Renee G. 1995. Grazing on regeneration sites encourages pine

seedling growth. Res. Paper PSW-RP-223. Albany, CA: Pacific Southwest Research Station,

Forest Service, U.S. Department of Agriculture; 11 p.

Effects of season-long, deferred-rotation, and rest-rotation grazing, on ponderosa pine (Pinus

ponderosa Doug!. ex Laws.) seedling growth and herbaceous vegetation control were studied in

regeneration sites at Boyd Hill, Modoc National Forest, California. Seedlings were planted in 1989.

Pine seedling survival and damage did not differ, but the seedlings were significantly taller, with

longer leaders with season-long grazing than without grazing. Treatment comparisons for plant

group and non-plant percent cover differed only for litter and bare soil, but cover and composition

of bottlebrush squirreltail (Elymus elY11loides [Raf.] Swezey) were greater without grazing.

Retrieval Terms: Ponderosa pine, Pinus ponderosa, survival and damage, range condition, cattle,

plantation

The Authors

RAYMOND D. RATLIFF, a range scientist (retired), and RENEE G. DENTON, a range

conservationist, are assigned to the Pacific Southwest Research Station's Sierra Nevada Montane

Ecosystem Research Unit, headquartered at 2081 East Sierra Avenue, Fresno. CA 93710.

Acknowledgments

We thank Big Valley Ranger District employees for their help in establishing this study. and

we thank all our summer aids who assisted with data collection.

Publisher

Pacific Southwest Research Station

Albany, California

(Mailing Address: P.O. Box 245, Berkeley, CA 94701-0245

Telephone: 510-559-6300)

March 1995
Grazing on Regeneration Sites

Encourages Pine Seedling Growth

Raymond D. Ratliff

Contents

Renee G. Denton

In Brief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. iii

Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1

Methods and Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1

Objective. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1

Study Area 1

Study Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1

Statistical Analyses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2

Results and Discussion 3

Seedling Survival and Growth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3

Plant Cover and Composition 4

Soil Surface Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7

Residual Dry Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7

Animallnt1uences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8

Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10
In Brief

Cattle grazing can be a useful tool for managing

regeneration sites. The effects of season-long, deferredrotation, and rest-rotation grazing, on conifer seedling growth

and herbaceous vegetation control were studied at Boyd

Hill, Modoc National Forest, in northern California. Wildfire

burned the area in 1978, regeneration sites were prepared in

1988, and ponderosa pine (Pinus ponderosa Doug!. ex Laws.)

seedlings were planted in 1989. Take-down fences were

used to simulate deferred-rotation and rest-rotation grazing

in a randomized complete block design on five sites. Pine

seedling survival and damage did not differ, but the seedlings

USDA Forest Service Res. Paper PSW-RP-223. 1995.

were significantly taller, with longer leaders with season-long

grazing than without grazing. Improved range conditions

(1989 to 1993) reflected natural recovery from site disturbance.

Treatment comparisons (1993) of plant group and non-plant

percent cover differed only for litter and bare soil, but the

differences were not between season-long grazing and no

grazing. Cover and percent composition of bottlebrush

squirreltail (Elymus elymoides [RaL] Swezey) were greater

without grazing than with season-long grazing. Soil surface

movement (except in the first year) and residual herbage

amounts did not differ between treatments.

iii
Introduction

Traditionally, a forester's job has been to grow trees.

After a wildfire on commercial forest land, the primary

objective is to obtain a vegetative cover that will conserve

soil, protect water quality, and reestablish the forest. Seeding

of grass species may be necessary, but grass (seeded or

natural) competes strongly with conifer seedlings (Larson

and Schubert 1969, Roy 1953). Competition is mostly for

soil moisture (Embry 1971, Larson and Schubert 1969).

Control of competing vegetation on regeneration sites

(plantations) helps assure a new stand of ponderosa pine

(Pinus ponderosa Dougl. ex Laws.) (McDonald and Fiddler

1989, Tackle and Roy 1953).

But how much grass is too much after seedling

establishment? Fiske (1984) hypothesized that grass

maintained at less than 50 percent of full site occupancy

would permit adequate stand development to meet typical

wood production objectives in California forests. Depending

upon location, others consider any amounts ofgrasses, forbs,

or shrubs undesirable at least until regeneration sites are 3-

to 5-years-old (McDonald and Fiddler 1986). Adequate levels

of grass control can be efficiently obtained by application of

herbicides. But herbicides cause concern for effects beyond

the target area. Alternate methods of controlling grass on

regeneration sites are, therefore, desirable.

Livestock grazing can be regarded as a tool for use in

forestry (Hatton 1924). At critical phenologic stages of

important herbaceous species, grazing should alter the plant

community and soil properties to favor conifer seedling

growth by regulating belowground as well as aboveground

competition (Karl and Doescher 1993). Timing and degree

of herbage use will largely govern grazing effectiveness.

To be effective, grazing must damage the competing

vegetation. Time of grazing should take advantage of natural

lows in plant carbohydrate reserves, and reserves of

carbohydrates generally decrease with early spring growth

(Smith 1972). Early spring grazing by livestock on regeneration

sites is a key to grass control (Fulgham 1985, Monfore 1983).

Controlling livestock so they will not browse the pine seedlings

is a critical consideration (McDonald and Fiddler 1989).

Stocking must be at a rate that will use 60 to 80 percent

of current forage production (Fulgham 1985, McDonald and

Fiddler 1989). Grazing can reduce water stress of seedlings

by reducing understory use of soil moisture (Carlson and

others 1994, Doescher and others 1989). Nevertheless, over

time, an effective treatment (while good for forest

regeneration) may produce an overgrazed range with

undesirable consequences to other vegetation and soil

resources (Leopold 1924, Sampson 1925).

"Grazing use should be based upon as complete utilization

ofthe forage resources as is consistent with forest production,

water-shed protection, pennanency of forage production,

game propagation and recreation" (Smith 1926: 139-140).

USDA Forest Service Res. Paper PSW-RP~223. 1995.

Kingery and others (1987) observed less damage to

conifer seedlings where rotation grazing was practiced, and

Karl and Doescher (1993) concluded that prescribed grazing

by cattle benefits the physiological status of seedlings.

However, those and other studies of livestock grazing in

regeneration sites did not determine whether some form of

rotation grazing would benefit conifer seedling growth.

This paper reports the results of our studies on pine

regeneration sites at Boyd Hill on the West Bieber Grazing

Allotment, Big Valley RangerDistrict, Modoc National Forest,

California from 1989 to 1993.

Methods and Materials

Objective

Our objective was to determine the relative effectiveness

of season-long grazing, specialized grazing management,

and no grazing for promoting seedling ponderosa pine growth

and controlling herbaceous vegetation. Also, we hoped to

learn whether better range conditions would result with

managed grazing of regeneration sites than with season-long

grazing or no grazing.

Study Area

Wildfire burned the Boyd Hill area in 1978. Soils there

are in the Lawyer and Elmore families (Luckow 1985). Both

families have loam to stony loam surface textures and clay

loam to cobbly clay loam subsoil textures. They are

well-drained, and permeability is moderately slow-0.5 to

1.5 centimeters (cm) water/hour. Effective rooting depths

range from 50 em to more than 100 em over basalt bedrock.

Hydrogen ion concentrations are in the slightly acid rangepH 6.1 to 6.5. The forest site class is 5, with potential

productivity in the range of 3.5 cubic meters (m') to 5.9 m'

per hectare per year.

Preparation for planting ponderosa pine in 1989 occurred

during the summer and fall of 1988. Standing dead trees and

shrubs were pushed into large piles with a brushrake-equipped

bulldozer and later burned. Plant cover, non-plant factors

(bare soil, gravel, rock, litter, wood, and animal waste), and

soil properties (bulk density, organic matter, soil water, and

water absorption) 1 year after site preparation were reported

by Ratliff and Denton (1991).

Study Design

Five regeneration sites were randomly selected for

establishing 64-m by 128-m study plots. To provide a

randomized complete block experimental design, each

plot consisted of four experimental units (EU) each 32 m

by 64 m (jig. 1). Blocking was dictated by differences

among the selected sites in slope, surface rocks, and preplanting vegetation.

1
128 m r-----------

Treatment A Treatment B

Season-Long Deferred-Rotation

64 m ----------1

Treatment D Treatment C

Control Ungrazed Rest-Rotation

Permanent fence Take down fence

om ':- -=-__---JL

Om 32m 64m

Figure 1-Generalized treatment arrangement used for plots in regeneration sites at Boyd Hill, Modoc National Forest, California.

We could not control livestock use within EUs of that

size. Incident grazing (use occurring under current allotment

management) was relied upon, and fencing was used to

simulate specialized management and provide protected

(ungrazed) controls. Treatments assigned were:

a) Unfenced, season-long grazing by livestock and wildlife.

b) Simnlated one unit of a two-nnit deferred-rotation

grazing program, using a take down fence.

c) Simulated one unit of a 3-unit rest-rotation grazing

program, using a take down fence.

d) Fenced, ungrazed by livestock hut available to wildlife.

Sampling units (SU) were two 3-m by 60-m belt transects

(Stoddart and others 1975) randomly located within each

EU. The first 1.5 m bordering each EU formed a buffer for

2

reducing side effects. Also, 1.5 m was the minimum distance

allowed between the two transects. All responses, except

pine seedlings and soil surface movement, were estimated

within the belt; and sample placement was random. The SUs

for conifer seedlings were 40 randomly located, healthy

seedlings within each EU. The SUs for soil surface movement

were 25 metal washers (1.91-cm diameter) placed 30 cm

apart on a 7.5-m transect randomly located in the EU. Similar

techniques had been used successfully for measuring erosion

(Gleason 1957).

Response units (RU) for plant groups (grasses, grasslike

plants, forbs, shrubs, and pine seedlings) and non-plant factors

(bare soil, gravel, etc.) were composed of 100 meter-long

sub-transects. Perpendicular to the center line of the SU,

sub-transects were randomized in the left-hand, center, or

right-hand meter of the belt transect. Because of time

constraints, the RU were composed of 50 randomly selected

sub-transects in 1993.

Plants and non-plant factors intercepted by each

sub-transect were measured to the nearest millimeter.

Projected crown intercepts were recorded for tree seedlings

and shrubs. Actual hasal intercepts were recorded for all

other characteristics. The sum of all intercepts equaled 100

percent cover. Plant intercepts were recorded by species, but

analyzed by groups. Gravel, litter, and bare soil were measured

individually on about a fifth of the sub-transects, and together

as surface on aU other sub-transects.

Conifer seedlings were identified by numbered tags

and plotted on a map of the EU to facilitate finding them.

Growth and survival were assessed each summer. Growth

was assessed as stem height and leader length and diameter

at 30 cm height. An RU was an individual seedling. Four

damage classes were recognized: dead, not apparent,

lateral, and terminal. Observed damage was assumed to

result from cattle or deer browsing or both. Survival and

damage classes were assessed as percentages ofthe original

40 seedlings.

For residual herbage amounts, the RU was a m' quadrat

(a 1/2 m' quadrat was used in 1993). RUs were randomly

located (without replacement) within the SU in the same

way as the sub-transects. In addition, heights and densities

of one to three forage species were recorded for each RU on

each block.

Herbage was defined as herbaceous, non-woody, plant

material, and was inclusive offorage and non-forage species

(e.g., grasses and thistles, respectively). Grazing use estimates

were based on amounts of residual herbage: ungrazed EUs

estimated total production, and treatment EUs estimated

amounts left.

Surface soil movement was assessed as a volume

calculated from the average vertical, horizontal, and depth

displacements of washers.

Statistical Analyses

The generalized hypothesis (H ) to be tested was that

seedling, herbaceous plant, or soil ~esponses do not differ

USDA Forest Service Res. Paper PSW~RP~223. 1995.
between grazing treatments. The alternate hypothesis (H)

was that some responses differ due to grazing treatment.

We used four treatments in five blocks of a randomized

complete block design. Treatment and block effects both

were fixed, and analysis of variance for that experimental

design was used.

For cover (species groups and non-plant factors), conifer

seedling survival and damage types, and soil surface

movement, statistically there was one measure per EU. The

appropriate analysis of variance had r = 5 blocks, t = 4

treatments, s =1 observation/block and treatment. Assuming

the block-treatment interaction is zero, the experimental

error mean square was the proper testing term. The arcsine

transformation was used for analyses of seedling damage

counts (expressed as percentages) (Steel and Torrie 1960).

Tukey's honestly significant difference (hsd) test was used

to separate treatment means. Alpha-level was set at 0.05,

but 0.10 was used for soil surface movement, because of

expected variation.

Observations per EU were 4 and 40 for residual dry

matter and seedling growth responses, respectively. The

number of dead seedlings varied. Variation among

observations (sampling error) was accounted for in the

analysis. The variance ofthe data measurements was assumed

to be constant. The appropriate analysis of variance for

residual dry matter had r = 5 blocks, t = 4 treatments, s = 5

observationlblock and treatment. The ANOVA model included

the block by treatment interaction. Separation of treatment

means for residual dry matter was by Tukey's hsd. Because

the numbers of seedlings and quadrats in which a forage

species was found varied, growth response means were

separated by contrasts, giving a Bonferoni "t" test with a

family alpha of 0.05.

Paired samples "t" (ex = 0.05) was used to test for

plant species groups and non-plant factor percentage cover

differences between 1989 and 1993.

Results and Discussion

Seedling Growth and Survival

Early researchers agreed that managed grazing by

cattle had little detrimental effect on regeneration (Stickel

and Hawley 1924), and damage to regeneration by cattle

was usually confined to overgrazed areas (Pearson 1927).

Proper grazing by cattle did not harm trees on conifer

regeneration sites at Blodgett Forest Research Station,

California; and the extent of damage to trees was the

same by cattle and deer as by deer alone (Kosco and

Bartolome 1983). Where cattle, deer, and elk were allowed

to forage, seedling loss was 44 percent compared with 25

percent where they were not allowed (Kingery and Graham

1991). Cattle damaged ponderosa pine seedlings by

trampling them, but most damage was done by deer and

elk browsing. Sheep grazing significantly increased

diameter growth of ponderosa pine and reduced cover of

competing vegetation without damaging the trees near

Klamath Falls, Oregon (Senter and Kelly 1987). But in

another study, in the Sierra Nevada of California, 10

years of sheep grazing did not enhance pine growth

(McDonald and Fiddler 1993).

In this study, grazing did not affect seedling survival.

All blocks and treatments showed that 72 percent of the

tagged seedlings survived (table 1). We found no differences

because of grazing treatment, but block effects were

significant. Blocks with the best survival were those that

were nearly level, while those with the poorestsurvival were

those with moderate to high degrees ofslope. No relationships

between seedling survival and non-plant factor or plant group

covers were found.

Grazing did affect seedling growth. Seedlings were taller

with season-long grazing than those that were protected

Table I-Average Ponderosa pine seedling survival, heights, leaderlengths, and diameters by grazing treatment

ill plantalions at Boyd Hill, Modoc National Forest, California, 1993.

Treatment Survival (pet.) Height (m) Leader (em) Diameter (em)

Season-long 74.0al 0.497 ±0.1902

a t9.750 ± 8.615. 1.257 ±0.540a

Deferred~rotation 73.0a 0.450 ± 0.170ab 16.808 ± 7.161b l.102 ±Oo402a

Rest-rotation 71.5a 0.468 ± 0.194ab 17.601 ± 7.804b l.171 ±Oo483a

Ungrazed 69.5a 0.446 ± 0.186b 16.101 ±8.191b 1.079 ± 0.429a

1 Column values followed by the same letter do not differ significantly at a family a = 0.05 by Bonferoni "t."

2 Average ± standard deviation based on the numbers of observations for all blocks.

USDA Forest Service Res. Paper PSW-RP-223. 1995. 3
from cattle. Similarly, leaders were longer with season-long

grazing than with the other treatments. Differences in diameter

were not statistically significant; nevertheless, the average

diameter was largest with season-long grazing and smallest

without grazing.

Cattle grazing did not increase damage to the seedlings,

and class of damage did not differ significantly between

treatments. Among the surviving seedlings, 64.8 percent had

no apparent damage, 4.9 percent had lateral branch damage,

and 30.4 percent had terminal bud damage.

Plant Cover and Composition

Increases in total plant and litter cover with decreases in

bare soil suggest lowered erosion potential, and hence,

improved watershed values. Increases in shrub coversuggest

greater hiding or escape potential, yielding improved wildlife

habitat values. Increases in perennial grasses without increases

in annual grasses or forbs suggest a higher forage potential,

and improved grazing values. These changes in cover and

composition suggest better ecosystem health, and improved

range resource values.

Total plant cover increased from 2.5 percent in 1989 to

8.1 percent in 1993. The largest increase was contributed by

shrubs (table 2). Percentage increases in cover were: tree

seedlings (495 percent), shrubs (355 percent), perennial grasses

(192 percent), and litter (44.6 percent). Bare soil decreased

by 36.4 percent and gravel by 23.3 percent. Although their

presence was observed in 1989, grasslike plants were first

intercepted in 1993. Surprisingly cover of annual grasses and

perennial or annual forbs were unchanged.

Grasses declined in their relative contribution to the

plant cover, but perennials made up 83 percent of the grass

cover in 1993 compared to 48 percent in 1989. Composition

of the plant cover (relative cover) in 1993 included pine

seedlings, 3.2 percent; shrubs, 80.9 percent; grasses, 9.2

percent (7.7 percent perennials and 1.5 percent annuals);

grasslike plants, 0.2 percent; and forbs, 6.4 percent (4.6

percent perennials and 1.8 percent annuals). These compare

with 1.7 percent, 56.9 percent, 17.6 percent, 0.0 percent, and

23.9 percent, respectively in 1989.

Increases in plant species on or around the study plots

between 1989 and 1993 suggest improved diversity (table

Table 2-Means, standard errors (SE), and 95 percent confidence intervals (CI)jor 1989 and 1993; and mean difference (1989-1993), "I" values

(1'), and probability oflite difference (P) for plant cover by species group and non-plantfactors, Boyd Hill, Modoc National Forest.

Group/factor Mean

1989

SE CI Mean

1993

SE CI Mean

1989-1993

T p

4

[Cover values for tree seedlings and shrubs were based on projected crown intercepts.

2Surface = (gravel + litter + bare soil). The difference between the mean value of "Surface" and the sum of the mean values of gravel, litter, and

bare soil is due to sampling intensity--N for surface is five times that for the components.

USDA Forest Service Res. Paper PSW~RP~223. 1995.
3). Eight species (two exotic perennial grasses, an exotic

biennial forb, and five endemic perennial forbs) not found in

1989 were found in 1993. Among the 57 species found

(conifers not included), 72 percent were endemics, 65 percent

perennials, 70 percent forbs, 23 percent grasses, 2 percent

grasslike plants, and 5 percent shrubs.

Increased species evenness (percent composition)

between 1989 and 1993 suggestslowered diversity. Although

not all the same, in 1993 and 1989 seven species had cover

values of 0.1 percent or more. Those from 1989 comprised

87.3 percent of the plant cover (Ratliff and Denton 1991),

while those from 1993 comprised 90.6 percent (table 3).

The species in 1993 were: western needlegrass (Aehnatherum oecidentalis [Thurber] Barkworth), cheatgrass brome

(Bromus teetorum L.), mahala mat (Ceanothus prostratus

Benth.), rubber rabbitbrush (Chrysothamnus nauseosus

[Pallas] Britton), yellow rabbitbrush (c. viseidiflorus

[Hook.] Nutt.), bottlebrush squirreltail (Elymus elymoides

[Raf.] Swezey), and mountain mule-ears (Wyethia molUs

A. Gray).

Among fourteen species common to all blocks in

1993, only yellow rabbitbrush and bottlebrush squirreltail

differed among treatments (table 4). Yellow rabbitbrush

composition was greater under season-long grazing than

under deferred-rotation, but we found no differences in its

cover percentages. Percentage composition and percentage

cover of bottlebrush squirreltail were both greater without

grazing than under season-long grazing. The averages

Table 3-Names, habits, andpercentcompositions ofunderstoryplantsonpineplantationsatBoydHill, Modoc NationalForest, 1989and1993.

Plant namesl Composition pet.

Scientific name

USDA Forest Service Res. Paper PSW-RP-223. 1995.

Common name Habit2 1989 1993

continues

5
Table 3-colltillued

Plant namesl

Scientific name Common name

Composition pet.

Elymus elymoides (Raf.) Swezey Bottlebrush squirreltail EN-PE-GR 0.642 2.655

Erigeron eatonii A. Gray

Navarretia species

Taeniatherum caput-medusae (L.) Nevski

Wyethia mollis A. Gray

Eaton fleabane

Dwarf skullcap

Meduesahead

Mountain mule-ears

EN-PE-FO

EN-PE-FO 12.694 1.881

6

ISources: scientific names, Hickman (1993); common names, Beetle (1970), Hickman

(1993), Niehaus and Ripper (1976), and/or Weeden (1975).

2Habit: EN = endemic, EX = exotic, AN = annual, BI = biennial, PE = perennial, FO = forb, GL = grasslike, GR = grass, SH = shrub.

3Dashes indicate that the species was observed but not intercepted. A blank indicates that the species was not observed.

USDA Forest Service Res. Paper PSW-RP-223. 1995.
increased from season-long to deferred-rotation to restrotation to no grazing.

Plant group or surface factor covers in 1993 did not

differ for the ungrazed and season-long grazing treatments

(table 5). Nevertheless, deferred-rotation and rest-rotation

had less litter cover and rest-rotation had more bare soil than

the ungrazed treatment. A greater number of blocks or a

longer time period or botb may be necessary for effects on

other species groups and factors to be manifested.

Soil Surface Movement

Soil movement was active during six observation periods

(July 1989 to July 1990 to May 1991 to July 1991 to May

1992 to July 1992 to July 1993). During all periods a washer

was displaced an average of 5.46 cm vertically (above or

below the transect line), 3.41 cm horizontally (left or right of

its initial position along the transect), and was covered by

0.41 cm of soil (table 6). On the basis of those averages, a

washer represented 1.27 cm3 of soil moved each period or

7.63 cm' during the study or 1.91 cm3

/year.

Nevertheless, we did not find treatment differences in

soil surface movement, except for the first year of the study

(table 6). That year (July 1989 to 1990) soil movement was

greater for rest-rotation than either season-long or

deferred-rotation grazing but no greater than without grazing.

Although cattle may have helped firm the soil in some areas

before fencing, the differences more likely reflect settling of

the soil after site preparation.

Residual Dry Matter

Whether grazed or ungrazed the amounts of material

left are apt to be the same. Amounts of residual dry matter

did not differ between treatments (table 7). Forage and

non-forage species, were not separated for analysis. Therefore,

non-forage species compensated for the weight of forage

species consumed by animals. Nature abhors a vacuum.

Nevertheless, from other information we found evidence

that grazing affected the residual dry matter.

Season-long grazing reduced culm heights of western

needlegrass by 9.8 percent, 14.6 percent, and 15.2 percent

compared with the deferred-rotation, rest-rotation, and

ungrazed treatments, respectively. While height/weight

relationships were not available for western needlegrass, the

height/weight relationships established for other grasses

Table 4--Percentage compositions by grazing treatment, analyses ofvariance (ANOVA), and Tukey's honestly significa1lt

differences (lIsd) at =0.05for plant speciesfollnd Oil all blocks, Boyd Hill, Modoc National Forest, 1993.

Grazing Treatmentl ANOVA'

Species3 SoL D·R R-R D-G F p hsd

------------------percenl compositiofl--------------------

Mountain mule-ears

6.153

2.340

2.943

3.353 2.516 3.513 0.140 0.934 6.608

lS_L =season-long grazing, D-R =deferred-rotation, R-R = rest-rotation, U-G = ungrazed (protected).

2p =P ratio (df =3,12) from ANOVA, P = probability of "F" occurring by chance.

3Species scientific names are given in table 3.

USDA Forest Service Res. Paper PSW-RP-223. 1995. 7
Table5-Coverlpercelltagesbygrazing treatment, analyses ofvariance (ANOVA), andTukey 's honestly signifiCa1l1 differences

(hsd) at a = O.OSforplallt groups and IlQn-plalltfactors, Boyd Hill, Modoc National Forest, 1993.

Grazing Treatmenf ANDYA'

Group/faclor SoL D-R R-R D-G F P hsd

-----------------~~------pe,.cellt cover---------------------------

Tree seedlings 0.302 0.250 0.154 0.318 0.142 0.933 0.825

Shrubs 6.170 9.682 4.620 5.826 0.909 0.466 9.586

Perennial grasses' 0.410 0.642 0.568 0.878 1.318 0.314 0.713

Annual grasses 0.080 0.160 0.132 0.128 0.955 0.445 0.145

9rasslikej}lants 0.012 0.024 0.030 0.012 0.441 0.728 0.059

Perennial forbs 0.520 0.348 0.216 0.406 2.026 0.164 0.371

:;AnriualJJ;bs ':' ,

Non-plant

, Animal waste

Rock 3.296 3.776 2.542 3.048 0.363 0.781 3.580

';Wo'bd'> 5.614 3.288 2.342':" 3.472 2.558 0.104 3.629

Surface4 83.264 81.386 88.982 85.508 1.940 0.177 9.848

drayei 2.950 2.656

Litter 45.258 59.262 5.838 0.01l 12.750

ICover values for trees and shrubs were based on projected crown intercepts.

2S~L = season-long grazing, D~R = deferred-rotation, R-R = resl-rotation, V-G = ungrazed (protected).

3p = P ratio (df = 3,12) from ANOVA, P= probability of UF" occurring by chance.

4Surface =(gravel + litter + bare soil); see explanation on table 2.

(USDA Forest Service, 1993) suggest that use of western

needlegrass was less than 10 percent by weight.

Neither heights nor density of bottlebrush squirreltail

differed due to treatment. The effect of season-long grazing

relative to no grazing on bottlebrush squirreltail cover and

percentage composition, therefore, resulted from a reduction

in individual plant basal area. Hormay and Talbot (1961)

found that clipping (defoliating) it once when its flower

stalks were low-in-the-boot reduced bottlebrush squirreltail

basal areas by 36 percent, and 4 years of clipping at the

seed-in-milk stage reduced basal areas by 62 percent.

Animal Influences

Cattle use occurred on all blocks in all years of the

study. Actual use on the West Bieber Allotment averaged

2,525 animal-months from 1988 to 1993 or about 95 percent

of the allowable use (Pope 1994). With incident grazing we

could not control the degree of forage use. Nevertheless, in

ourjudgment, forage use on EUs open to season-long grazing

was moderate, considering both years with low and years

with ample precipitation. Within the deferred and rest-rotation

EUs, time and degree of use depended on cattle being in the

regeneration sites when the fences were down.

No differences were found in animal waste percentage

cover (table 5). Nevertheless, based on the averages, animal

waste covered about twice the area in the other treatments as

in the ungrazed EUs where it covered an average of 3.0 m2

.

That finding suggests use of the deferred and rest-rotation

EUs when they were open to cattle. Even so, forage use in

those treatments seldom approached levels that could be

expected were the systems implemented on the allotment.

Deer were abundant in the area early in the study, but

the population declined markedly by 1993. The counts on

64-kilometer-long transects (inclusive of the Boyd Hill area

herd) dropped from 50 in 1992 to 36 in 1993 to 19 in 1994

(Stowers 1994). Given no treatment difference in damage to

or survival of pine seedlings and the animal waste in the

ungrazed EUs, we assumed that deer had an influence on the

8 USDA Porest Service Res. Paper PSW-RP-223. 1995.
Table 6--Average washer displacement and soil movementforthe study period, soil movementforthe

July 1989~90period, and Tukey's honestly significant difference (hsd) at a:= 0.10 by grazing treatment

in plantations at Boyd Hil~ Modoc National Forest, California.

Washer displacementl Soil movement2

Treatment ab be cd A B 1989-90

-_~.•~.~~~~._-~~~(cm)-~_~------------- -----------------(c/llJ) -----------------

Season-long 4.85 3.38 0.39 1.64 1.07 0.34z

Deferred-rotation 5.39 3.06 0.40 2.11 1.10 0.35z

Rest-rotation 6.34 3.75 0.54 3.20 2.14 2.74y

Ungrazed 5.29 3.46 0.33 2.75 1.01 1.09yz

hsd 2.75 1.47 0.21 2.81 2.20

1 Average washer displacement. ab:= vertical (above or below the transect line); bc := horizontal (along

the transect line); cd := depth (covering with soil).

2 Soil movement:= volume estimated by washer displacement. A:= average over all periods; B = average

based on average displacements; 1989-90'" average for the period July 1989 to July 1990 (values with like

letters are not significantly different).

Table 7-Average residual herbage dry matter and heightsl and densitiesfor western needlegrass2 and

bottlebrush squirreltail by grazing treatment, Boyd Hil~ Modoc National Forest, 1990~93.

Grazing Treatment3 ANOVA4

Factor SoL D-R R-R U-G F P

Dry matter (gmJm2) 91.59 92.21 99.43 87.16 0.253 0.859

Western needlegrass

height (cm) 44.41b 49.26a 52.01a 52.39a 5.000 0.002

density (plants/m2

) 4.72 5.49 4.14 3.66 1.688 0.171

Bottlebrush squirreltail

height (cm) 29.54 27.49 27.59 31.13 1.388 0.249

density (plants/m2

) 3.16 3.07 2.52 3.38 1.046 0.0375

I Row values followed by a different letter are significant at a = 0.05 by mean differences.

2Species scientific names are given in table 3.

3S-L = season-long grazing, D-R '" deferred-rotation, R-R = rest-rotation, U-G = ungrazed (protected).

4p = P ratio (df'" 3,79) from ANOVA, P = probability of"P" occurring by chance.

USDA Forest Service Res. Paper PSW-RP-223. 1995. 9
pine seedlings. That deer had little effect on other vegetation

is suggested by the animal waste to grass and forb ratio

which was 1 unit to 11.5 units in the ungrazed BUs, about a

third as high in the other treatments.

Conclusions

Range conditions (based on cover and composition)

have improved since the regeneration sites were planted in

1989. Improvement without grazing reflects natural recovery

from site disturbance (preparation for planting). No differences

in cover between the season-long and ungrazed treatments

in 1993 means that conditions improved using both treatments.

Seedling survival did not differ among treatments at

Boyd Hill, suggesting no detrimental effect of cattle grazing.

Nevertheless, season-long grazing, as it occurred at Boyd

HiJI, was better than no grazing for promoting conifer seedling

growth. The pine seedlings were taJIer and leaders were

longer under season-long grazing than without grazing.

Differences were not found among treatments in types of

damage to seedlings, suggesting that deer browsing was a

major influence.

Grazing can affect species cover and percentage composition as shown by bottlebrush squirreltaiL Nevertheless,

season-long grazing, compared with no grazing, did not

effect shrub or total perennial grass cover.

A longer period and a tightly controJIed, large-scale

study wiJI be necessary to define the effects of deferredrotation and rest-rotation grazing on pine seedling

development in plantations. Such specialized grazing

management should, nevertheless, produce seedling growth

as good as or better than without grazing.

Forage and other herbaceous vegetation in regeneration

sites increases and then decreases as the trees grow and

become dominant. IdeaJIy, forest management will coordinate

grazing of regeneration sites and permanent range areas to

take advantage of the positive effects on seedling growth.

The problem is attaining proper stocking, distribution, and

time of use. The key is attention to grazing management.

References

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Doescher, Paul S.; Tesch, Steven D.; Drewien, William E. 1989. Water

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10

Embry, Robert S. 1971. Soil water availability in an Arizona mixed

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Fiske, John. 1984. Site evaluation for determining grass competition.

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Hormay, A. L.; Talbot, M. W. 1961. Rest-rotation grazing..•A new

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Rept. 51. Washington, D.C.: Forest Service, U.S. Department of

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Karl, Michael G.; Doescher, Paul S. 1993. Regulating competition on

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39(3): 405-418.

Kingery, James L.; Graham, Russell T.; White, Jeffrey S. 1987. Damage

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11
The Forest Service, U.S. Department of Agriculture, is responsible for Federal leadership in forestry.

It carries out this role through four main activities:

• Protection and management of resources on 191 million acres of National Forest System lands

• Cooperation with State and local governments, forest industries, and private landowners to help

protect and manage non-Federal forest and associated range and watershed lands

• Participation with other agencies in human resource and community assistance programs to

improve living conditions in rural areas

• Research on aU aspects of forestry, rangeland management, and forest resources utilization.

The Pacific Southwest Research Station

• Represents the research branch of the Forest Service in California, Hawaii, American Samoa

and the western Pacific.

The policy of the United States Department of Agriculture,

Forest Service prohibits discrimination on the basis of race,

color, national origin, age, religion, sex, or disability, familial

status, or political affiliation. Persons believing they have been

discriminated against in any Forest Service related activity

should write to: Chief, Forest Service, USDA, P.O. Box 96090,

Washington, DC 20090·6090.
United States

Department of

Agriculture

Forest Service

Pacific Southwest

Research Station

Research Paper

PSW-RP-223

m

Grazing on Regeneration Sites Encourages Pine Seedling Growth

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