27

Slightly altered sites have an abundant understory

of herbaceous species associated with sagebrush

steppe and moderate levels of conifer overstory.

These sites usually respond quickly to changes in

livestock grazing and fire management. Severely

altered sites contain lower amounts of herbaceous species associated with sagebrush steppe

as a result of intense grazing regimes or greater

conifer overstory coverage. Recovery of sagebrush is rapid owing to efficient seed transport

(Bunting et al. 1987, Ferguson 2001). Once the

local seed sources of herbaceous species have

been lost, however, recovery of this type after

change in grazing management or conifer removal is slow.

Within the basin BLM- and FS-administered

lands, this PVT only occurs as a few large patches when mapped at 1-km resolution (Hann et al.

1997, ICBEMP source data). These large patches are scattered and infrequent across central

and southern Idaho and central Oregon. However, based on plot data, historical and current oblique landscape photography, and midscale photo

interpretation, much of this PVT actually occurs

in small undetectable (at 1-km mapping resolution) patches. On moist aspects or high elevations, it is intermingled with large patches of the

mountain big sagebrush–mesic east, mountain big

sagebrush–west, and mountain big sagebrush–

mesic west with juniper PVTs; on the drier aspects of the dry and cold forest types throughout

the foothills and mountains of Idaho, western

Montana, eastern Washington, and Oregon (Hann

et al. 1997, Hessburg et al. 1999). Although this

PVT is more prevalent in the eastern portion of

the basin, the mountain big sagebrush–mesic east

with conifer PVT can be found throughout the

basin where this environment occurs. It is estimated that because of the limitations of the mapping resolution, this PVT may actually occur with

a greater geographic range and an area increased

by as much as 50 percent.

Most of this type occurs at moderate elevations

(table 3) in the moderate precipitation zone (table 4).

Mountain Big Sagebrush–Mesic

West PVT

Mountain big sagebrush typically dominates the

mountain big sagebrush–mesic west PVT, which

is found west of the Bitterroot Mountains (figs.

7 and 8). Other common shrubs include yellow

rabbitbrush and antelope bitterbrush. Herbaceous

species are similar to those found in the mountain

big sagebrush–mesic east PVT, but this type

lacks species typical of the shortgrass prairie.

Although invasive annual grasses occur within

this PVT, they seldom dominate unless livestock

grazing or other disturbance has severely impacted the site. Spotted and diffuse knapweed have

increased in some localities. Much of this PVT

had a shorter fire-return interval during historical

times (Bunting et al. 1987, Houston 1973, Miller

and Rose 1999, Miller and Wigand 1994), and

some changes in composition reflect this decrease in fire occurrence resulting from active

fire suppression and reduction of fine fuels by

livestock grazing. Cold winters with little snow

coverage may result in widespread sagebrush

foliage mortality (Hansen et al. 1982).

The presence of invasive species and increased

mountain big sagebrush density characterize

slightly altered conditions in this PVT. Dense

mountain big sagebrush primarily reflects fire

suppression. However, most native species are

generally present. Slightly altered sites respond

rapidly to changes in livestock and fire management.

Severely altered sites within this PVT most frequently result from improper livestock management and lack of fire. Early seral native and

invasive species typically dominate the understory. Mid- and late-seral understory species are

often substantially reduced.

Within the basin BLM- and FS-administered

lands, this PVT was a dominant type with many

large patches when mapped at a 1-km resolution

(Hann et al. 1997, ICBEMP source data). These

large patches occur throughout the mountains,

plateaus, and plains of southeastern Oregon and
28

southwestern Idaho. Most of this type occurs at

moderate elevations (table 3) in the moderate and

low precipitation areas (table 4).

Mountain Big Sagebrush–Mesic West

with Juniper PVT

The mountain big sagebrush–mesic west with

juniper PVT has many shrub and herbaceous

species in common with the mountain big sagebrush–mesic west PVT. Woodland vegetation

dominates late-seral stages, which have increased

greatly following Euro-American settlement.

Utah juniper dominates woodlands in southeastern Idaho and adjacent Wyoming (figs. 7 and 9).

Singleleaf pinyon also may be present in southeastern Idaho. Western juniper, without pinyon,

dominates southwestern Idaho and eastern Oregon. Portions of this PVT also can contain stands

of curlleaf mountain-mahogany. Substantial

changes in understory vegetation accompany

succession from sagebrush steppe to juniper

woodland (Miller et al. 2000, Miller and Wigand

1994). Reduction in fire frequency has been

commonly credited as the cause of woodland

expansion, but livestock grazing and climatic

change have been important interacting factors

(Burkhardt and Tisdale 1976, Miller and Rose

1999, Miller and Wigand 1994).

This PVT occurs in a mosaic with juniper or

locally pinyon-juniper woodlands. Plant species

composition is similar to the mountain big sagebrush–mesic west PVT. Juniper often encroaches after alteration of the fire regime (Burkhardt

and Tisdale 1976, Miller and Rose 1999, Miller

and Wigand 1994). Seed dispersal into the sagebrush steppe is facilitated by animal consumption

of the juniper fruits (Chambers et al. 1999a,

1999b). Slightly altered sites generally include

small juniper and most native sagebrush steppe

plant species. These sites respond rapidly to

changes in fire management to achieve restoration.

Severely altered sites have typically developed

into woodlands. Woodland development normally

results in a reduction of fine fuels, making sites

more difficult to burn. The resulting loss of sagebrush steppe species increases the recovery time

Figure 8—This example of the mountain big sagebrush–mesic west PVT, located near Fairfield, Idaho, is

dominated by mountain big sagebrush and antelope bitterbrush. (Photo by Stephen Bunting.)
29

after fire (Bunting et al. 1999). Woodland development often results in increased soil erosion

further increasing recovery time (Davenport et al.

1998). Some sites with substantial soil erosion

may no longer be capable of supporting sagebrush steppe vegetation.

Within the basin BLM- and FS-administered

lands, this PVT was a dominant type with many

large patches when mapped at a 1-km resolution

(Hann et al. 1997, ICBEMP source data). Although the modal type occurs extensively in central Oregon, this type has a range across all the

foothills and mountains of eastern Oregon and

southern Idaho. Most of this type occurs at moderate and low elevations (table 3). Most occurs in

the low precipitation zone, with a lesser amount

(38 percent) in the moderate precipitation areas

(table 4).

Wheatgrass Grassland PVT

The wheatgrass grassland PVT was typically

dominated by bluebunch wheatgrass and Sandberg bluegrass under historical conditions (figs.

10 and 11). Much of the original area has been

converted to agricultural use. The remaining area

has been severely altered by excessive livestock

grazing and invasive species. Cheatgrass and

medusahead were introduced early in the 20th

century. More recently, common crupina, yellow

starthistle, and several species of knapweed have

been introduced and are displacing native species

and earlier invaders on many sites. Wildfire is

common and aids the conversion from native to

invasive species dominance. However, fire is not

essential in the conversion to invasive species.

Slightly altered sites usually include many invasive

species such as cheatgrass, Japanese brome,

medusahead, and yellow starthistle (Daubenmire

1975a, Roché and Roché 1988). It is virtually

impossible to completely eliminate these welladapted invasive species (Tisdale 1986). However, aggressive weed control measures and

changes in livestock management may prevent

increasing invasive plant dominance and additional displacement of native species. Perennial grass

Figure 9—Example of mountain big sagebrush–mesic west with juniper PVT in an early stage of western juniper

encroachment located south of Jordan Valley, Oregon. (Photo by Stephen Bunting.)
30

Figure 10—Area included in the wheatgrass grassland, antelope bitterbrush, mountain shrub, fescue grassland, and fescue

grassland with conifers potential vegetation types within the interior Columbia basin as mapped at the 1-km scale. ICBEMP data

on file with: USDA Forest Service, Pacific Northwest Research Station, P.O. Box 3890, Portland OR 97208.
31

communities respond well to changes in livestock

management, but little is known about the restoration of perennial native forbs.

Invasive species dominate severely altered sites,

and few native species may remain. To restore

these areas, aggressive, active restoration measures are needed, which may include control of

invasive species and seeding of native species.

Within the basin BLM- and FS-administered

lands, large patches of this PVT detectable at

1-km resolution mapping are thinly scattered

across northern Oregon, southern Washington,

central Idaho, and western Montana (Hann et al.

1997, ICBEMP source data). However, based on

plot data, historical and current oblique landscape

photography, and midscale photo interpretation,

much of this PVT actually occurs in small, undetectable (at 1-km mapping resolution) patches on

dry aspects of rugged river breaks and foothill

terrain intermingled with dry and cold forests and

with mountain big sagebrush PVTs, or in rugged

terrain intermingled with agricultural lands. Most

of this type occurs at low and moderate elevations (table 3). Almost equal amounts occur in

low and moderate precipitation zones (table 4).

Antelope Bitterbrush PVT

The antelope bitterbrush PVT is most extensive

in the basin in central Washington (fig. 10). It

is dominated by bitterbrush and has a perennial

herbaceous understory dominated by one or more

grasses including bluebunch wheatgrass, Idaho

fescue, rough fescue and needle-and-thread

(Daubenmire 1970, Mueggler and Stewart 1980,

Youtie et al. 1988). On less steep slopes with

sandy soils, needle-and-thread dominated the

understory but has often been replaced by cheatgrass (Daubenmire 1970, Youtie et al. 1988). The

PVT often occurs on coarse-textured soils that

permit greater rates of recruitment for bitterbrush

than sites with heavier textured soils (Nord 1965).

These communities are important as a source of

landscape diversity and for providing forage for

wild ungulates (Griffith and Peek 1989, Ngugi

et al. 1992). Periodic high populations of the

Figure 11—Remaining wheatgrass grassland PVT vegetation is often located in steep canyon country

associated with the Snake, Salmon, Clearwater, Grande Ronde, and Imnaha Rivers. This example is from

Corral Creek, a tributary of the Snake River, Hells Canyon, Idaho. (Photo by Sandra Robins.)
32

western tent caterpillar (Malacosoma californicum Packard) may cause extensive damage and

mortality to bitterbrush if the defoliation persists

for 2 years (Clark 1956, Furniss and Barr 1975,

Nord 1965, Tisdale and Hironaka 1981).

Invasive annual grasses and secondary invasive

weedy species such as knapweed have severely

altered much of this PVT. Invasive annual grasses also have fueled increased fire occurrence,

and this has reduced the abundance of bitterbrush

in many areas. Some areas currently with dense

stands of bitterbrush are vulnerable because the

stands are becoming extremely old and recruitment rates are low.

Within the basin BLM and FS lands, few large

patches of this PVT were detectable at 1-km

resolution mapping (Hann et al. 1997, ICBEMP

source data). However, based on plot data, historical and current oblique landscape photography,

and midscale photo interpretation, much of this

PVT actually occurs in small undetectable (at

1-km mapping resolution) patches on foothill and

mountain slopes, ridges, and benches as inclusions

in dry forests and in mountain big sagebrush or

fescue grassland PVTs. Most of this type occurs

at moderate elevations (table 3) and in the moderate precipitation zone (table 4).

Mountain Shrub PVT

The mountain shrub PVT is usually located in

the transition between shrub steppe and conifer

forest vegetation (fig. 10). The vegetation is

often regarded as a stable community, but at least

some stands are probably seral to many coniferous forest types (Christensen 1964). Little information is available on this PVT. It is dominated

by a variety of shrubs often associated with

mesic shrub steppe and dry conifer communities

such as mountain big sagebrush, antelope bitterbrush, Utah serviceberry, Saskatoon serviceberry,

shinyleaf ceanothus, ninebark, curlleaf mountainmahogany, common choke-cherry, and bitter

cherry (Major and Rejmanek 1991). On some

sites, small quaking aspen may be common. This

PVT occurs as relatively small patches interspersed with other PVTs, and, consequently, its

area is often underestimated. The mountain shrub

PVT also may occur as stringers of shrubdominated vegetation in draws. These stringer

communities may be particularly important to

vertebrates such as mountain quail (Oreortyx

pictus) because of the proximity of water and

tall dense shrub overstory (Brennan et al. 1987)

that provides added structure to the landscape.

Mountain shrub communities also provide valuable browse for large ungulates. Therefore the

PVT is more important than its areal extent

indicates. The mountain shrub communities are

often surrounded by vegetation such as sagebrush steppe that frequently burns and therefore

is susceptible to fire. However, most shrub species exhibit moderate to high resprouting potential

and recover quickly (Cook et al. 1994, Gartner

and Thompson 1973, Leege 1979, Leege and

Hickey 1971, Morgan and Neuenschwander

1988, Noste et al. 1989, Young 1983).

Within the basin BLM- and FS-administered

lands, few large patches of this PVT were detectable at 1-km resolution mapping (Hann et al.

1997, ICBEMP source data). However, based on

plot data, historical and current oblique landscape

photography, and midscale photo interpretation,

much of this PVT actually occurs in small patches on foothills, mountain slopes, and draws as

inclusions in dry and cold forests and in mountain

big sagebrush or fescue grassland PVTs, or in

rugged terrain intermingled with agricultural

lands. These patches are detectable with finer

resolution mapping. Much of this type occurs at

high and moderate elevations (table 3). Most

occurs in the moderate and low precipitation

zones (table 4).

Fescue Grassland PVT

The fescue grassland PVT is found in western

Montana where it is dominated by rough fescue

or Idaho fescue (Mueggler and Stewart 1980),

in central Idaho where it is dominated by Idaho

fescue, and in northeastern Oregon where the

dominants are Idaho or green fescue (Johnson

1987) (fig. 10). Other common codominant

grass species include bluebunch wheatgrass,

Hood’s sedge, western needlegrass, and prairie
33

junegrass. Common forbs include lupine, geranium, and arrowleaf balsamroot. Fescue grasslands

form on a variety of site conditions from subalpine ridges to lower forest-grassland transitions

where sagebrush species do not occur.

The most prevalent cause of alteration is improper past grazing. Slightly altered sites often show

a reduction in the fescue species and bluebunch

wheatgrass and an increase in the shallow-rooted,

less productive grasses (Dormaar and Willms

1990, Johnson 1987, Reid et al. 1991). Sites that

are more severely altered may be totally dominated by short-lived weedy forbs (Revel 1993).

Looman (1969) estimated that more than 90 percent of the Canadian fescue grasslands had been

moderately to severely altered. These sites deteriorate rapidly under improper grazing and may

require more than 20 years to recover after management changes (Dormaar and Willms 1990,

Reid et al. 1991). Leafy spurge and knapweed

are common invasive species in portions of this

PVT (Best et al. 1980, Olsen and Wallander

1998, Tyser and Key 1988).

Within the basin BLM and FS lands, the large

patches of this PVT detectable at 1-km resolution

mapping are scattered across northern Oregon,

southern Washington, central Idaho, and western

Montana (Hann et al. 1997, ICBEMP source

data). However, based on plot data, historical

and current oblique landscape photography, and

midscale photo interpretation, much of this PVT

actually occurs in small patches of rugged river

breaks and foothill terrain intermingled with dry

and cold forests and with mountain big sagebrush

PVTs; such patches are detectable with finer

resolution mapping. This type occurs at both moderate and high elevations (table 3). Most of the

type is found within the moderate and high precipitation zones (table 4).

Fescue Grassland with Conifer PVT

The fescue grassland with conifer PVT has a

geographic distribution and herbaceous composition similar to that of the fescue grassland PVT

(fig. 10). However, it occurs in a mosaic of conifer PVTs and may have a scattered overstory of

Douglas-fir, lodgepole pine, subalpine fir, or other

conifers. Response of grazing is similar to that

of the fescue grassland PVT. In the absence of

fire, conifers tend to increase on this PVT, and

the understory species composition changes from

grassland species to one more similar to dry conifer vegetation.

Within the basin BLM and FS lands, the large

patches of this PVT detectable at 1-km scale

mapping are widely spread across northern Oregon, southern Washington, central Idaho, and

western Montana (Hann et al. 1997, ICBEMP

source data). However, based on plot data, historical and current oblique landscape photography,

and midscale photo interpretation, additional

portions of this PVT also may occur in patches

intermingled with dry and cold forests and with

mountain big sagebrush PVTs; such patches are

detectable with finer resolution mapping. This

type occurs primarily at both moderate and high

elevations (table 3). Most is found within the

moderate and high precipitation zones (table 4).

Primary Causes of PVT Alteration

Workshop participants identified the causes that

were most significant in altering the composition

and function of rangeland vegetation in the basin

(table 5). Identification of the causes allows managers to better develop strategies for restoration.

Of the many causes of alteration of rangeland

vegetation in the basin, five were considered most

significant in terms of severity of effect and total

area of the basin affected: (1) introduction of

invasive species, (2) livestock grazing, (3) modified fire regimes, (4) climatic change, and (5)

activities related to human presence (urbanization,

agriculture, road development, etc.). It was recognized that perhaps native ungulates also altered

vegetation, but the areal extent of these sites is

not known. The relative importance of the causes

of alteration differs with location. For example,

agriculture has had a major effect on the Snake

River plain and central Washington but a minor

effect on eastern Oregon and northern Nevada.

All five causes often occur in synergistic feedback loops, are magnified by climatic changes,

and are strongly interrelated in their effect on
34

Table 5—Primary factors contributing to and severity of alteration of each of 17 rangeland

potential types found within the interior Columbia basin

Votes for most

Potential vegetation type (PVT) Primary factors highly altered a

Salt desert shrub Past livestock grazing, invasive species, 11b

increased fire occurrence

Wyoming big sagebrush–warm Past livestock grazing, invasive species, 16b

 increased fire occurrence

Wyoming big sagebrush–cool Past livestock grazing, invasive species 2

Basin big sagebrush Agricultural development, past livestock grazing, 7b

invasive species, increased fire occurrence

Threetip sagebrush Past livestock grazing, invasive species, 0

increased fire occurrence

Low sagebrush–xeric Past livestock grazing, invasive species 2

Low sagebrush–mesic Past livestock grazing, invasive species 1

Low sagebrush–mesic with juniper Decreased fire occurrence 1

Mountain big sagebrush–mesic east Decreased fire occurrence, invasive species 2

Mountain big sagebrush– Decreased fire occurrence, invasive species 0

 mesic east with conifers

Mountain big sagebrush–mesic west Decreased fire occurrence, past livestock grazing 9b

Mountain big sagebrush– Decreased fire occurrence, past livestock grazing 14b

 mesic west with juniper

Wheatgrass grassland Invasive species, past livestock grazing 10b

Antelope bitterbrush Invasive species, past livestock grazing, 2

increased fire occurrence

Mountain shrub Decreased fire occurrence 5

Fescue grassland Invasive species, past livestock grazing 0

Fescue grassland with conifers Decreased fire occurrence, invasive species, 2

past livestock grazing

a A low number does not indicate that alteration has not occurred within a PVT; rather, it indicates the degree or extent of

alteration is low relative to other PVTs found in the basin.

b Considered among the most highly altered PVTs and having high priority for restoration practices.
35

vegetation. For example, invasive annual grasses

affect both the fire regime and competition. More

frequent wildfire occurrence increases the dominance by invasive annual grasses (Pellant 1990,

Peters and Bunting 1994, Whisenant 1990). The

introduction of invasive species also alters the

competitive relation among species (Harris 1967,

Klemmedson and Smith 1964) and other ecosystem processes (Vitousek et al. 1996). Livestock

grazing potentially alters the competitive relations

among species as well. It also may increase the

spread of invasive species (Mack 1986) and alter

the fire regime (Bunting et al. 1987). Thus, it is

usually impossible to identify a single or even a

primary cause of vegetation alteration.

Other factors also were noted as important influences for some areas in the basin. Agricultural

development fragments many landscapes (Harms

et al. 1987, Knick and Rottenberry 1997) and

resulted in the initial introduction of many invasive

species (Mack 1986). Climatic variation (Blaisdell

1958, Sauer and Uresk 1976), climatic change

(Hu et al. 1999, Miller and Wigand 1994, Steig

1999, Tausch 1999a, Tausch and Nowak 2000,

Whitlock and Bartlein 1997), and type conversion

efforts such as seeding, herbicidal control of

sagebrush (Blaisdell et al. 1982, Blaisdell and

Mueggler 1956), and mechanical control of juniper and sagebrush (Blaisdell et al. 1982, Evans

1988) also were cited as important factors in

some areas of the basin. Feral horse populations,

which were greatest in the 19th century (Ryden

1978, Thomas 1979, Wagner 1983), remain locally

important factors and may have great impact on

those areas (Beever 1999, Beever and Brussard

2000).

Participants were asked to identify the primary

and secondary causes of alteration for each of

the basin’s PVTs (table 6). Some participants did

not think that they were adequately familiar with

the vegetation of the entire basin and did not

complete this exercise. Participants did not agree

as to which factors were most important for the

different PVTs. Livestock grazing (past and

current) (Daubenmire 1940, Miller et al. 1994,

Tisdale 1986), invasive species (Kindschy 1994,

Mack 1981, Melgoza and Nowak 1991, Tausch

et al. 1994, Tisdale 1986), and changes in fire

occurrence (Bunting et al. 1987, Miller and

Wigand 1994, Pellant 1990, Whisenant 1990)

were most often cited as the primary factors

that have affected extensive areas within the

basin, but the relative importance of these differed between PVTs (table 6).

Of the 17 dry grass, dry shrub, and cool shrub

PVTs identified in the basin, workshop participants identified the PVTs that most significantly

influence management of federal lands at the

broad scale (table 7). This selection was based on

the degree of alteration, aerial extent of the PVT,

and the importance of the PVT to the overall

ecological function of the basin. Considering the

basin-wide scale, these six PVTs have a high

priority for restoration. At the local scale, however, others may deserve greater priority for restoration activities. Knowing the causal factors

related to alteration is important when planning

restoration methods. Participants identified the

primary and secondary factors contributing to the

alteration of the six PVTs (table 6). Livestock

grazing was most often cited as the primary or

secondary cause of altered PVTs, followed by

invasive species and change in fire regime. The

effects of past and current livestock grazing were

separated.

The ramifications of not restoring the PVTs are

expected to be significant to the future stability of

these areas, but the magnitude of change differed

across the six PVTs considered (table 7), such

as the extent to which vegetation community

composition had changed. Mountain big sagebrush–mesic west was predicted to change the

least, whereas the other five PVTs showed moderately high or high levels of vegetation composition change. Two PVTs showed low levels of

predicted change in physical processes, whereas

the remaining four PVTs displayed moderately

high to high levels of change. Four PVTs showed

low degrees of system stability with the remaining

two rated as having moderately high degrees of

stability. The basin big sagebrush PVT had the

highest predicted risk of continued decline. All
36

other PVTs showed moderately high risk. All six

PVTs were considered to be generally predictable in the direction of future trend for these ecosystem characteristics. The following discussion

of the options for restoration will focus on the six

most altered PVTs previously identified.

Management Options and

Feasibility for Restoration

Appropriate restoration technique depends on

vegetal and environmental conditions, and degree

of alteration. As previously discussed, particular

sites in a PVT differ along a continuum from only

slightly altered to extremely altered. Slightly altered conditions typically contain low levels of

invasive species, have been minimally affected

by livestock grazing and other human impacts,

and have fire regimes that, although changed

from the historical period, have not resulted in

significant alteration of vegetation composition

and function. Extremely altered conditions often

exhibit high levels of invasive species, livestock

grazing, and other impacts. Fire may contribute

to altered conditions by either occurring more or

less frequently than it did prior to Euro-American

settlement because fire occurrence is affected

by herbivory, invasive species, human activity,

and direct fire suppression.

Restoration of slightly altered conditions often

may be readily achieved by changing management of the causative factor(s); i.e., changing

management of invasive species, livestock, or

fire. This has been referred to as passive restoration management (Allen 1995). Severely altered

conditions often include extirpation of natural

Table 6—Number of participants ranking cause as primary and secondary in alteration of six

rangeland potential vegetation types (PVT) in the interior Columbia basin

 Causes of alteration

Priority Other

potential humanvegetation Change in Climate Invasive Livestock related Other

type (PVT) Ranking fire regime change species grazing factors causes

Salt desert shrub Primary 0 0 3 10 1

Secondary 4 2 5 0 0

Unranked 3

Wyoming big sage- Primary 1 0 1 10 1

brush–warm Secondary 2 0 7 0 0

Unranked 2

Basin big sagebrush Primary 0 0 1 8 2

Secondary 4 0 4 2 2

Unranked 4

Mountain big sage- Primary 4 0 0 3 1

brush–mesic west Secondary 2 0 0 5 0

Unranked 4

Mountain big sage- Primary 7 0 0 2 1

brush–mesic west Secondary 2 0 0 3 4

with juniper Unranked 5

Wheatgrass Primary 0 0 3 8 3

grassland Secondary 0 6 6 1 2

Unranked 3
37

species and their seed sources, loss of soil, and

changes in the physical environment. Restoration

of such sites requires management that is much

more active, such as seeding of native or other

desirable species or the use of prescribed fire.

Restoration also was considered to have one of

three primary objectives. First, it may be done to

prevent future alteration. An example of this situation may be the application of prescribed fire or

natural ignition wildland fire use in an ecosystem

that is currently within the historical range of

variability (HRV), but in which the trend in vegetation change is moving outside the HRV owing

to the lack of fire occurrence. The HRV has

been defined as the ecological conditions of an

ecosystem, and the spatial and temporal variation

of these conditions, that occur when the ecosystem is relatively unaffected by people (Landres

et al. 1999, Morgan et al. 1994). Second, restoration may be done to stabilize an ecosystem that

is currently altered but still contains all the essential ecosystem elements. These sites can be restored through passive restoration activities.

Third, restoration may require active and sometimes substantial management effort to restore

a poorly functioning ecosystem. These are obviously the most difficult sites to restore and may

require management activities that are not ecologically or economically feasible on a broad

scale.

The feasibility of restoration, related to four criteria of the six most severely altered PVTs in the

basin, was discussed by the workshop participants (table 8). When rating “ecological feasibility,” consideration was given to whether or not

irreversible changes had occurred in portions of a

PVT that precluded the possibility of restoration.

These included factors such as changes in soil

characteristics or invasive species that had become a permanent part of the site’s flora. When

considering the “time required for response,” it

was recognized that the response time for restoration would be highly variable within a PVT

because it is dependent on the degree of alteration. Time estimates reflecting the most typical

situation within a given PVT were categorized as

short (≤10 years), moderate (11 to 49 years), and

long (≥50 years). The “probability of success”

criterion incorporated probable climatic variation

and other stochastic factors as they influence the

Table 7—Degree of change in site characteristics expected with no restoration intervention for

severely altered potential vegetation types in the interior Columbia basin

 Potential vegetation type

Mountain Mountain

Salt Wyoming Basin big sage- big sagedesert big sage- big brush– brush–mesic Wheatgrass

Characteristic shrub brush–warm sagebrush mesic west with juniper grassland

Composition Moderately High High Moderate Moderately Moderately

changed high high high

Physical Low High High Low High High

processes

changed

Degree of Moderately Low Moderately Low Low Low

stability high high

Risk of Moderately Moderately High Moderately Moderately Moderately

continued high high high high high

decline

Predictability High High High High High High
38

success of restoration activities. For example,

when reseeding native species is necessary in the

more arid PVTs, several years of above-average

precipitation are needed to assure successful

establishment. Because this is an unlikely event

that cannot be predicted prior to seeding, establishment from a single seeding in PVTs like the

salt desert shrub has a low probability of success.

Possible restoration activities were evaluated for

“economic feasibility” as low, moderate, or high,

but the data to develop monetary values were not

available. Thus, the economic feasibility categories assigned to PVTs in table 8 are relative

among the six PVTs considered.

The potential restorations of the six most altered

PVTs in the basin are discussed below as considered at the basin-wide scale. Local conditions and

objectives must be included when planning any

restoration program, and these often will include

factors not discussed here.

Salt Desert Shrub PVT

Restoration of the salt desert shrub PVT is challenging because of the harsh environment. Low

precipitation and saline soils are especially challenging (Blaisdell and Holmgren 1984, Bleak et al.

1965) in their effects on seed germination and

growth (Roundy et al. 1984). Individual sites are

often highly fragmented and embedded in a mosaic of sagebrush steppe vegetation that further

isolates them from natural seed sources. Even

when seedling establishment is achieved, populations of shrubs and grasses often decline within

10 to 12 years (Blaisdell and Holmgren 1984,

Hull 1963). However, West (1979) found that

most seedlings persisted for long periods if they

survived the second year after establishment.

Common causes of failure include poor seed germination, unadapted species or ecotypes, improper seedbed preparation or planting techniques,

competition, climatic variation, and frequent wildfires on the more altered sites. Rehabilitation

efforts in the past often have failed owing to severe site conditions and lack of attention given to

high ecotypic variation that is common within this

PVT (Blaisdell and Holmgren 1984, Bleak et al.

1965). It is critical to match plant species used in

restoration to the soil type. Indigenous animals

cause a significant loss of seedlings through herbivory but also may be important in the natural

recruitment of some species (Longland 1995).

In general, three restoration scenarios exist

within the salt desert shrub PVT. The first

scenario includes communities that have been

slightly altered and where there has been little

change in the native perennial shrub and herbaceous plant cover. The second scenario describes

Table 8—Feasibility and response time for restoration options in severely altered potential

vegetation types within the interior Columbia basin

Response to restoration options

Ecological Time required Probability Economic

Potential vegetation type feasibility for responsea of success feasibility

Salt desert shrub Low Long Low Low to moderate

Wyoming big sagebrush–warm Moderate Moderate Moderate Moderate

Basin big sagebrush Moderate Moderate Moderate Moderate

Mountain big sagebrush– High Short High High

mesic west

Mountain big sagebrush– Moderate Moderate High Moderate

mesic west with juniper

Wheatgrass grassland Low Long Low Low

a Time required for response: Short <10, moderate 11–49, and long >50 years.
39

sites where the vegetation has been moderately

altered, generally to the extent that the perennial

herbaceous component has been reduced or eliminated and often replaced by annual grasses. The

third scenario describes the most altered state

where the perennial shrubs and herbaceous plants

have been replaced primarily by annual grasses.

Recovery of slightly altered sites generally can

occur under passive management and proper

livestock grazing (Blaisdell and Holmgren 1984,

Holmgren and Hutchings 1972). Livestock grazing management must be flexible, however, to

accommodate the extreme environmental variation from one year to the next. Winter use by

domestic animals is most feasible (Cook and

Stoddart 1963). Winter livestock grazing when the

soil is frozen or snow covered is recommended

when managing for biological soil crusts (Belnap

et al. 2001).

Sites within the salt desert shrub PVT that have

been slightly to moderately altered can be restored through proper livestock management,

fire prevention, and aggressive management of

invasive species (Blaisdell and Holmgren 1984).

However, recruitment of native species on moderately altered sites may require long periods.

Consequently, restoration of many sites will

require artificial establishment of native species.

Knowledge of the agronomic requirements of

some shrub species such as fourwing saltbush,

spiny hopsage, and winterfat is available (Clary

and Tiedemann 1984, Durrant et al. 1984, Pellant

and Reichert 1984, Shaw and Hafercamp 1994,

Shaw and Monsen 1984), but little is known about

others (budsage and shadscale). Herbaceous

species should be seeded without removal of

the shrub overstory when possible, to maintain

the seed source of the shrub species (Blaisdell

and Holmgren 1984). This usually can be accomplished with the rangeland drill. However, establishment of native herbaceous species is difficult

at best, and most stands of introduced species

decline within 10 to 12 years (Plummer 1966).

Forage kochia has been successfully used

(Clements et al. 1997, Monsen and Turnipseed

1990, Stevens and Van Epps 1984) but may act

as an invasive species. Harrison et al. (2000)

found that forage kochia successfully competed

with annuals, especially cheatgrass, halogeton,

medusahead, and tumblemustard and may spread

into disturbed and bare areas. However, they

found no evidence that it was an aggressive invader or overcame established perennial plant

communities.

The sites within the salt desert shrub PVT that

offer the greatest challenge for restoration are

those that have been severely altered, are dominated by annual grasses, and where wildfires

occur frequently. Restoration of native species

usually requires controlling competing vegetation

through mechanical or herbicidal means and restricting wildfire. Desired species can then be

established through seeding or transplanting of

container or bareroot stock (Luke and Monsen

1984). The inability to control competition and

wildfire in the past has resulted in failure to

adequately restore many of these sites to predisturbance conditions. As such, the feasibility

for restoration on sites altered the most severely

was generally considered to be quite low and

in some situations not possible.

Wyoming Big Sagebrush–Warm PVT

The restoration needs in the Wyoming big sagebrush–warm PVT are staggering owing to the

immense area involved. This PVT covers more

than 9 million ha in the basin (table 2) and an

extensive additional area outside the basin.

Much of the area has been altered by past livestock use, invasive species, agricultural development, and changed fire regimes. Seed sources

for sagebrush and many perennial herbaceous

species have been extirpated from many sites in

central Washington and the Snake River plain.

Frequent disturbance also potentially alters the

nitrogen cycle of these sites (Bolton et al. 1990).

Wildfires repeatedly burn large areas of annualdominated steppe and create additional annualgrass-dominated areas each year throughout the

basin (Pellant 1990, Whisenant 1990). Restoration

usually requires (1) fire suppression, (2) control

of invasive plant competition, (3) input of native
40

plant seeds or transplants, and (4) changes in

livestock management to encourage plant recruitment. Efforts that do not provide for all four

components are likely to fail. Establishment of

native species has been difficult because of low

summer precipitation (Hironaka et al. 1983), inadequate restoration technology, and limited seed

sources.

Perhaps the most feasible action is to prevent

further alteration of those areas that are at risk

but only slightly to moderately altered through

changes in management of fire, invasive species,

and grazing. Recovery through natural recruitment processes is possible but occurs slowly, and

full restoration may take a long time (Eckert and

Spencer 1986, Wambolt and Payne 1986). Cheatgrass and other invasive species likely will remain

as a component of this vegetation, regardless of

the level of restoration achieved (Kindschy 1994,

Tisdale and Hironaka 1981). Restoration strategies primarily include changes in livestock management necessary to prevent further depletion

of the understory and fire suppression to prevent

loss of the shrub component. Fire suppression

may be difficult because these communities often

are surrounded by stands of annual grasses that

are prone to fire. Weed management may be

necessary to prevent further invasion by invasive

forbs.

Although establishment of introduced perennial

grasses through direct seeding has proven successful (Hull 1974, Keller 1979, Mueggler and

Blaisdell 1955), establishment of native species

has been problematic in this PVT (Blaisdell 1958,

Miller et al. 1986). Interseeding and transplanting

into annual and introduced perennial grass communities have been used successfully to diversify

species composition and establish native species

(Stevens 1994). Annual grass competition inhibits

the recruitment of most native herbaceous species with the exception of bottlebrush squirreltail

(Harris 1967, Hironaka 1994). It is evident that

competition from annual grasses must be controlled prior to seeding with either introduced or

native species (Miller et al. 1986). This has been

accomplished with varying success by livestock

grazing, burning, mechanical treatments, and

herbicide applications (Hull and Holmgren 1964,

Ogg 1994, Pellant et al. 1999, Vallentine and

Stevens 1994). Other factors contributing to the

failure of native perennial species recruitment

include availability of adapted species or ecotypes

(Meyer 1994, Meyer and Monsen 1992), poor

seedbed conditions (Call and Roundy 1991,

Roundy 1994), climatic variation (Meyer 1994,

Millar 1997, Miller et al. 1986, Tausch 1996),

altered small-herbivore populations (Hardegree

1994), and altered soil conditions (Allen 1995,

Stahl et al. 1998). In recent years, greater research emphasis has focused on the establishment of native perennial species.

Highly altered sites exist over a wide continuum

of conditions, but three categories of conditions

frequently occur. Firstly, the shrub overstory remains with a depleted herbaceous understory.

These most frequently have developed under

improper grazing management. In many cases,

the coverage of sagebrush has increased on these

sites. Mechanical treatments have been successfully used to temporarily reduce sagebrush canopies and increase presence of herbaceous species

(Blaisdell et al. 1982, Mueggler and Blaisdell

1958). However, if adequate populations of desirable herbaceous species are not present, seeding

will be necessary. Establishment of the shrubs

and dominant perennial grasses is feasible, and

recruitment requirements of these species have

been studied (Blaisdell et al. 1982, Meyer 1994,

Meyer and Monsen 1990, Roundy 1994). The

recruitment requirements for native perennial

forbs in this PVT are not well understood. The

feasibility of restoration for all four criteria (table

8) is moderate.

Secondly, both native shrub and herbaceous

components are largely absent, and the site is

dominated by annual invasive species such as

cheatgrass and medusahead, and perennial invasive forbs such as rush skeletonweed. These

most often have developed when the first type

of site conditions (sagebrush overstory-depleted

understory) has burned by wildfire and no postfire rehabilitation was done or those that were

attempted failed (Laycock 1991). Abandoned

cropland also has resulted in more areas of
41

annual-grass dominated communities. Sagebrush

recruitment occurs when a nearby seed source

exists. However, repeated wildfires remove the

seed source from extensive areas and may result

in modified soil environments making natural

sagebrush recruitment less likely (Allen 1995,

1988). Restoration usually includes controlling

invasive species competition and seeding of both

herbaceous species and sagebrush. Some researchers recommend seeding of sagebrush after

the herbaceous species are established to reduce

competition between native species. Meyer

(1994), however, indicates that herbaceous seedlings may also compete with young sagebrush

seedlings. Because sagebrush establishes best

when planted at or near the surface, broadcast

seeding may be more effective than drill seeding

(Meyer 1994). The feasibility of restoration is

moderate to low because of (1) moderate to high

costs, (2) moderate probability of success, and

(3) moderate time for response. The primary

objective of these treatments would be to establish a functional shrub steppe ecosystem that

would eventually repair itself. The restoration of

some components such as biological soil crusts

may take a long time.

Thirdly, introduced perennial grasses, such as

crested wheatgrass, dominate the site. These

have been seeded after wildfire occurrence or

mechanical removal of sagebrush. Sagebrush

recruitment can occur on these sites when a seed

source is available and other conditions are favorable, but what makes these conditions favorable

is not understood. Restoration of sites seeded to

introduced-perennial species has not been widely

studied but appears to be feasible if competition

by the introduced perennial grasses can be reduced (Bakker et al. 1997, Sheley and Larson

1997). Because the introduced species keep lessdesirable species out of the community through

competition, these may have a lower priority for

restoration than those more subject to further

degradation.

Basin Big Sagebrush PVT

Considerations and feasibility for restoration of

the basin big sagebrush PVT are similar to those

of the Wyoming big sagebrush–warm PVT.

Many severely altered sites occur as one of the

three categories mentioned previously: (1) sagebrush overstory-depleted understory, (2) invasive

annual grass dominated, and (3) introduced perennial grass seedings. Many remaining areas not

under intensive agriculture often are embedded in

a mosaic of other vegetation types, particularly

Wyoming big sagebrush steppe (Hironaka et al.

1983) and may be isolated from other similar

sites. These areas are generally small, occurring

on the terraces adjacent to water courses, and

are not mappable at the 1-km scale. Many of

these patches of basin big sagebrush PVT embedded within the Wyoming big sagebrush PVTs

(warm and cool) have been severely altered by

higher herbaceous productivity, which increases

wildfire risk, invasive species problems, and influence of livestock grazing. The more developed

deeper soils, as compared to Wyoming big sagebrush steppe, increase the probability of establishment of herbaceous species (Hironaka et al.

1983). This may increase the feasibility of restoration as compared to the Wyoming big sagebrush steppe. Prior to the 1970s, this sagebrush

subspecies was not separated taxonomically from

Wyoming big sagebrush (Beetle 1960; Winward

1970, 1980; Winward and Tisdale 1977), and the

ecology of these subspecies is confounded in the

older literature. Little information specific to this

PVT related to restoration or management exists.

Harniss and McDonough (1976) found greater

year-to-year variation in seed germination in basin

big sagebrush than in Wyoming big sagebrush.

Daubenmire (1975a) stated that sagebrush overstory benefitted the growth of native herbaceous

plants and cheatgrass by modifying the microenvironment and enhancing the soil nutrient status

from leaf fall.

Mountain Big Sagebrush–Mesic

West PVT

Slightly altered sites of the mountain big sagebrush–mesic west PVT usually contain all the

elements necessary for recovery following

changes in management. This PVT is perhaps

the most resilient of those found in the basin and
42

often responds to changes in livestock management (Eckert and Spencer 1986, Yeo et al. 1990).

Mountain big sagebrush occurs with greater density and coverage than other sagebrush species

(Hironaka et al. 1983), and reduced fire occurrence has resulted in many sites with high shrub

coverage. Canopy coverage of mountain big

sagebrush rarely exceeds 40 percent (Winward

1970, Bunting et al. 1987). High coverage of

sagebrush reduces the abundance of understory

species. Fire often is used to reduce the influence

of sagebrush in these communities. Mountain big

sagebrush rapidly becomes reestablished if a

seed-producing population is present and the fire

is not severe (Bunting et al. 1987). Seedlings

also may rapidly establish from seed in the soil

(Hironaka et al. 1983), but germination is enhanced by stratification (McDonough and Harniss

1974) or a heat treatment (Chapin and Winward

1982). Nelle et al. (2000) reported that mountain

big sagebrush had developed 8 percent canopy

coverage on 6- to 14-year-old burned areas,

whereas the nearby unburned areas had 18 percent coverage. On large severely burned areas,

it may require more than 30 years for the sagebrush to fully recover (Blaisdell et al. 1982).

Antelope bitterbrush is often associated with

this PVT and usually recovers rapidly through

resprouting and seedling establishment (Bunting

et al. 1984). However, resprouting is highly

correlated to the season of the fire and to

growth form. The greatest resprouting potential

is observed on spring burns and from the shorter

multiple-stemmed growth forms (Bunting et al.

1984). Mechanical and herbicidal treatments

also have been used extensively to reduce sagebrush coverage in the past (Blaisdell et al. 1982,

Mueggler and Blaisdell 1958, Wambolt and Payne

1986), but these practices are less common today

owing to economic and environmental concerns

(Klebenow 1970, Schroeder and Sturges 1975).

Because sagebrush establishment occurs rapidly,

disturbances that maintain open to mid-density

sagebrush must be frequently applied (15- to 30-

year intervals).

Most perennial herbaceous species respond positively to fire, but Idaho fescue may be reduced

depending on the severity of the burn (Bunting

et al. 1987, Harniss and Murray 1973, Hironaka

et al. 1983). Native herbaceous plants will increase on burned sites if there are adequate

onsite seed sources. This PVT has a diverse

perennial forb component, particularly in areas

with higher precipitation. Perennial forbs that are

enhanced by postfire conditions include arrowleaf

balsamroot, lupine, senecio, penstemon, and

hawksbeard.

Severely altered conditions are dominated by

annual and short-lived forbs and grasses resulting

primarily from improper grazing practices. Seeding native herbaceous species on depleted sites

may be necessary because rest from livestock

grazing alone may not be effective in restoring

them (Holmgren 1976). The greater precipitation

and cooler climate of this PVT increase the probability of seeding success as compared to many

other sagebrush steppe communities. Those sites

with a depleted herbaceous component or domination by invasive species may require seeding.

Establishment of common grass and shrub species is highly feasible (Blaisdell et al. 1982), but

less is known about the establishment requirements of native perennial forbs. Those sites dominated by invasive forb species such as knapweed,

yellow starthistle, or leafy spurge may be the

most difficult to restore within this PVT. Biological control of these species has shown potential

but has not proven to be fully successful at this

time (Jacobs et al. 2000, Maddox et al. 1991,

Muller-Scharer and Schroeder 1993, Rinella et al.

2001). Grazing by sheep has been shown to be

effective in reducing leafy spurge (Bowles and

Thomas 1978, Olsen and Wallander 1998).

Restoration of the mountain big sagebrush–mesic

west PVT may be the most feasible of the six

most altered PVTs found within the basin (table

8). It is one of the most resilient PVTs of the

rangeland vegetation types, responding readily to

changes in management. The changes in fire

regime and livestock grazing were considered

about equal as primary causes of alteration (table

6). The response time was considered to be short,

and the probability of success high for this PVT

(table 8). Prescribed fire and wildland fire use

can open sagebrush canopy where it is greater
43

than desired. Prescribed fire was predicted to

be moderate in cost, short in response time, and

have a high probability of success. Mechanical

treatments also have been successfully used in

the past, but these treatments are limited by increased economic costs, topography, and soil

conditions that reduce their feasibility.

Mountain Big Sagebrush–Mesic West

with Juniper PVT

The species compositions of the seral stages of

mountain big sagebrush–mesic west with juniper

PVT are similar to that of the mountain big sagebrush–mesic west PVT. Many of the restoration

considerations for the two PVTs are the same.

The primary difference is the presence of adjacent juniper woodlands that expand into this PVT

in the absence of fire and dominate the later stages of succession (Miller and Wigand 1994). The

woodland-dominated stages of succession have

widely different restoration potentials and considerations. Restoration can be readily achieved by

reintroducing fire in the early stages of woodland

development (Bunting 1987) (fig. 9). The livestock grazing regime must be altered, at least

temporarily prior to burning, to permit adequate

fuels to accumulate. Postburn livestock grazing

strategies must allow for herbaceous plant recovery, seed production, and recruitment.

As the more advanced woodland stages develop,

a threshold is crossed (Tausch 1999b) that affects

the potential fire behavior and postfire successional pattern. Fine fuel loads decline in the community making prescribed fire more difficult to

implement (fig. 12). Community composition

becomes dominated by species typical of juniper

woodlands, and many species typical of sagebrush steppe decline (Bunting et al. 1999). When

fires do occur, they are more intense and severe

(Gruell 1999) causing greater mortality of herbaceous species. Plant canopy coverage for site

protection takes increasingly longer to redevelop

postburn leaving the site more susceptible to

further soil erosion. In some portions of the basin,

Figure 12—An example of the mountain big sagebrush–mesic west with juniper PVT in the midstage of western

juniper encroachment located on the Owyhee Plateau, Idaho. Advancing succession results in a reduction of the

species associated with sagebrush steppe. (Note the skeletons of dead and dying sagebrush and antelope

bitterbrush in the juniper interspaces.) (Photo by Stephen Bunting.)