Sagebrush-Steppe Ecology

Introduction

When you think of a “Sagebrush Steppe Ecosystem” what do you think of? Do you think of sagebrush? Do you think of endless miles/acres of nothing but gray? Do you think of desert? Do you think of rangeland? Do you think of some of the wildlife observed there – pronghorn, sage grouse, jackrabbits? Do you think of vast, open space with distant mountains in the background? Do you think of public land – BLM, Idaho Endowment Land, Forest Service? Do you think of recreational opportunities – off-road vehicle use, hunting? Do you think of a wasteland in need of management for more productive uses? Writers tell us that these descriptors, and even more, were used by Europeans pioneers as they trekked across the sagebrush steppe, and then began to settle and eke out livelihoods in the deserts of western United States. However, sagebrush steppe ecosystems are much more than any of these or even all of them combined.

When we talk about an “Ecosystem” we are talking about more than just the plants or wildlife that occur on an area. We are talking about a “System” where all of the living organisms are interacting with and sustaining one another in conjunction with the soil and climate. As with all systems – mechanical, political, chemical, etc., there is a continuous flux of the different parts as they strive to maintain equilibrium. Ecosystems are not static – they are continually changing in both time and space. Ecosystem changes are in response to both endogenous (factors occurring within the system) and exogenous (factors from outside the system) factors.

There is much variability in the soils, climate, elevation, species, and production across the range that the sagebrush steppe occurs. There is also much variability in species, climate, and production over time. Therefore, although we frequently refer to the sagebrush steppe as an “ecosystem” across the range that it occurs it is composed of many different ecosystems. This is certainly true within the scale that we usually evaluate and manage sagebrush steppe. Thus, when

Chapter Goals:After completing this chapter, volunteers should be able to:

Gain an understanding of an ecosystem vs. plant community Learn about some of the sagebrush communities found in Idaho Gain an understanding for classifying the condition and trend of ranges Introduce state, transition, and disturbance in determining the health of sagebrush steppe

communities Gain an appreciation for sagebrush steppe ecosystems

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we manage a sagebrush-grass area we need to understand both the inherent characteristics of that particular site and also the characteristics of that particular site at the present time.

In this class, we are going to learn that the sagebrush steppe of western United States is much different today than it was when the pioneers trekked across it. We are going to learn that the ecosystem itself is functioning much different today than it did prior to European settlement. And we are going to learn that we humans ourselves have played a major role in these changes. We are also going to learn that the future of the sagebrush steppe of western United States is dependent upon us – not only our understanding of the workings of the ecosystem, but our appreciation that we have for it as a society.

Distribution

The distribution or range of the sagebrush steppe ecosystem depends on climate and has fluctuated over the past 30 millennia. In general, big sagebrush favors areas that receive the majority of the precipitation during winter months and the least during summer months. Annual precipitation amounts range from about 6 in. to about 22 in. Soils are quite variable and include the moderate to deep loess’s, alluvial, lacustrine, and sedimentary deposits, and volcanic deposits of basalt, andesite, rhyolite, and tuff. Topography ranges from nearly flat to gently rolling to relatively steep.

The sagebrush steppe ecosystem extends over much of Utah, Nevada, southern Idaho, eastern Oregon, western Montana, Wyoming, and Colorado, as well as smaller disjunct areas of eastern Montana, southern British Columbia, southern Alberta, southwestern North Dakota, western South Dakota, Washington, California, Arizona, and New Mexico. Estimates of total acreage vary from some 95 million acres to 270 million acres. Even if the lower estimate is accepted as reasonably accurate, sagebrush-grass vegetation is still one of the largest, if not the largest, range ecosystem in the western United States. However, it is estimated that the area occupied has been reduced by 40-50 percent since pre-European settlement and less than 10 percent remains in an unaltered condition today. Millions of acres have been converted to agriculture, cities, roads, transmission lines, energy developments, exotic plants, and woodlands. More will be said about the management of the sagebrush steppe in the next class.

Sagebrush − Soil Relations

Soil type considerations are very important in the distribution of sagebrush taxa. Although there are many exceptions, the general distribution of sagebrush is related to soil moisture, temperature, depth, and parent material. Some observations regarding soil relations in the Pacific Northwest are summarized in the following paragraphs.

In general, basin big sagebrush tends to occupy the deep soils with minimal development in the low to moderate precipitation zone, whereas Wyoming big sagebrush occupies soils of moderate depth. As moisture conditions and temperature improves with increase in elevation, mountain big sagebrush dominates until it gives way to sub-alpine sagebrush on deep soils at high elevations. The position of tall three-tip sagebrush along the moisture gradient overlaps the upper portion of

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Wyoming big sagebrush and the lower portion of mountain big sagebrush. Apparently, it is not associated with a particular kind of soil.

On shallow soils, dwarf sagebrush species replace the tall species. Black sagebrush occupies the lower position along the moisture gradient and is restricted to limestone-derived soils in the drier areas. Where low sagebrush is associated with black sagebrush, the former consistently occurs in the cooler and higher moisture situations. Low sagebrush also occurs on shallow, non-calcareous soils with strongly developed clay-pans in southwestern Idaho and eastern Oregon. These soils are supersaturated during the spring, but during the summer the plants are under considerable moisture stress. Alkali sagebrush occurs in habitats similar to those that support low sagebrush on shallow soils with clay-pans. Sometimes both species are found in the same stand. Fringed sagebrush also occurs on similar habitats, but on the more shallow and rocky portions.

Sagebrush Steppe Plant Communities

Native sagebrush-grass vegetation is dominated by woody species of Artemisia with an understory of perennial grasses and forbs. Vegetal cover is usually not continuous and considerable bare ground is often exposed. Sagebrush generally occurs at elevations from 5,000 to 7,000 ft., but some species grow at elevations as low as 800 ft. and others as high as 11,500 ft. On some soils and under some moisture conditions the sagebrush over-story is co-dominant with other species of woody plants.

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The native sagebrush steppe ecosystem was dominated by an over-story of woody sagebrush (Artemesia) and an understory of perennial grasses (primarily wheatgrasses, fescues (Festuca), bluegrasses (Poa), and wildryes) and perennial forbs. Other important shrubs include rabbitbrush (Chrysothamnus), bitterbrush (Purshia), horsebrush (Tetradymia), chokecherry (Pnrnus), serviceberry (Amelanchier), hopsage (Grayia), Mormon tea (Ephedra), wild currant (Ribes), mountain mahogany (Cercocarpus), and snowberry (Symphoricarpos). Forbs were present in a much greater variety than grasses, but their distribution was much less uniform. However, one species, arrowleaf balsamroot (Balsamorhiza sagittata), was very widespread and often abundant. Other common forbs present in varying quantities were yarrow (Achilles), pussytoes (Antennaria), locoweed (Astragalus), segolily (Calochortus), hawksbeard (Crepis), larkspur (Delphinium), daisy (Erigeron), buckwheat (Eriogonum), biscuitroot (Lomatium), lupines (Lupinus), foxglove (Penstemon), phlox (Phlox), groundsels (Senecio), violet (Viola), mulesears (Wyethia), and deathcamas (Zigadenus). These forbs are highly variable in characteristics, ranging from mat-formers such as Phlox hoodii and Antennaria to tall, coarse plants such as Balsamorhiza and Lupinus leucophyllus. Root systems vary from stout, deep taproots in the latter two species to spreading, rhizomatous systems in others.

Today we find an understory with fewer perennial grasses and forbs and increasingly dominated by non-native annual grasses and forbs. This is especially true for the Great Basin area, where cheatgrass (Bromus tectorum) oftentimes dominates the understory as a monoculture, and to a lesser extent for the intermountain and Wyoming Basin areas.

We typically classify sagebrush steppe by the dominant species of big sagebrush e.g. basin big sagebrush, Wyoming big sagebrush, or mountain big sagebrush present. However, although big sagebrush species have the widest distribution, there are smaller acreages dominated by the “low” sagebrushes. Also, there are usually multiple sagebrush species occurring together in the same area.

Common Sagebrush Communities of Idaho

Big sagebrush (Artemisia tridentata) is an erect, aromatic, evergreen species, that lacks winter buds. It has numerous ecotypes that range in size from 1 ft. to 5 ft. tall. Growth forms are of two types; multi-stemmed and single trunks and are correlated with sub-specific taxonomy. This species produces two types of branches, vegetative and flowering. The bark on older vegetative branches is stringy and black or dark brown in color. Bark on younger vegetative and inflorescences is heavily covered with trichomes that give the branches a silvery green to gray color. The leaves are also silvery green or gray.

There are three widely recognized subspecies of big sagebrush. Subspecies can be separated on morphological, chemical, and ecological characteristics. Wyoming big sagebrush occupies the drier sites that range from 8 to 13 in. of precipitation, 12 to 60 in. for mountain big sagebrush with basin big sagebrush somewhat between the other two subspecies. Some authorities have

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divided mountain big sagebrush into three forms, varieties, or subspecies depending on the authority being quoted. One is called subalpine big sagebrush, A. t. ssp. spiciformis, or A. t. ssp. vaseyana f. spiciformis. The second is referred to as “X” big sagebrush, or xeric big sagebrush or A. t. ssp. xericensis. Lastly, a variety of mountain big sagebrush is called A. t. ssp. vaseyana var. pauciflora.

Big sagebrush grows in a variety of soils throughout its range from arid plains, valleys, foothills, to mountain slopes, from 1,500 to over 10,000 ft. elevation. It can be found growing on all 12 soil textural classes, but it is most often found on loams or sandy loams. Two soil characteristics are common: they are well-drained and contain low concentrations of salts.

Depending on subspecies, as many as 40 species of grasses and forbs can grow with big sagebrush. Big sagebrush is not fire tolerant and can be killed by a number of pathogenic fungi, insects, and environmental conditions such as winter kill or winter induced drought. Seed dispersal is highly variable among stands and somewhat dependent on elevation; some starting in mid-fall, others not until early winter. Most seeds germinate immediately after snow melt or after late-winter or early spring storms. The seeds possess no special adaptations for wind dispersal, but are wind dispersed to a maximum distance of about 100 ft. from the mother plant under most environmental conditions. Hence seedlings placement is heavily depended on wind direction from the seed source. Big sagebrush forms a weak soil seed bank. A single mature big sagebrush plant can produced upward of 500,000 seeds, although, excessive browsing can reduce inflorescences production by a factor of 20. The seeds must lie on the soil surface or be buried not more than 0.25 in. for successful emergence.

Basin big sagebrush (A. t. ssp. tridentata) is normally an erect shrub 3 to 6 ft. tall with numerous spreading branches giving it a “ragged-top” appearance, it can reach a height of 15 ft. and trunk diameter of 10 in. when growing in deep well drained, sandy soils of sheltered areas. Vegetative branches are numerous. The whole plant is light gray-green in appearance because of the appressed pubescence. The location of flowering stalks is variable – some occurring above the vegetative branches and some occurring within the vegetative branches. The young bark is light brown or silvery but often becoming black with age and shredding. Basin big sagebrush is easily killed by fire. It exhibits a preference for deep, well-drained soils in valley bottoms and lower foothill areas at elevations of 5,000 to 7,000 ft. This preference makes it a good indicator of arable land. Much of the area once occupied by basin big sagebrush is now under cultivation.Basin big sagebrush is the least palatable of the big sagebrush complex to both livestock and wildlife. The shrub may supply some shelter, especially in severe winters, and it may serve as emergency winter feed because of its height, but the plants are not normally sought out by any type of large herbivore.

Most basin big sagebrush sites that have not been heavily grazed or disturbed support a diverse productive herbaceous understory. However, if the understory is weakened by heavy grazing and the sagebrush canopy becomes closed these sites become unproductive unless management is implemented to reduce the canopy cover and reduce grazing pressure.

Wyoming big sagebrush (A. t. ssp. Wyomingensis) is seldom over 3 ft. tall, branches from the base have a twisted and irregular growth form. Flower stalks generally do not extend above the

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vegetative branches giving the appearance of rounded top. It tends to have a rounded “cushion-like” appearance and is the dominant big sagebrush species of the Great Basin and Wyoming Basin. Wyoming big sagebrush has grayer and somewhat less fan-shaped leaves than black sagebrush and the seed stalks are less persistent. It tends to produce more lateral roots in the upper soil horizons that other big sagebrush taxa.

Wyoming big sagebrush is common on dry, warmer soils at elevations of 5,000 to 7,000 ft. When Wyoming big sagebrush and black sagebrush occur in intermixed stands, Wyoming big sagebrush occupies deeper soil.

Soils are of lower fertility and dryer than the soils of other big sagebrush taxa. Therefore, understory herbaceous vegetation is less diverse and productive than under either basin big sagebrush or mountain big sagebrush. On the lower part of the Great Basin, where soils are warmer, exotic annual herbaceous vegetation becomes the dominant understory with excessive livestock grazing and/or disturbance.

Wyoming big sagebrush is palatable to both livestock and big game, especially in winter, and in areas where livestock or big game winter in stands of Wyoming big sagebrush the plants are heavily browsed. In most instances this plant supplies enough browse, on relatively poor soils, that it should be encouraged rather than discouraged. Wyoming big sagebrush is very susceptible to fire.

Mountain big sagebrush (A. t. ssp. vaseyana) is a uniformally growing, flat-topped shrub up to 3.5 ft. tall and a trunk up to 4 in. in diameter even in plants more than 100 years old. Branches spread at the base and frequently layer. Vegetative branches are usually less than 3.5 ft. high, numerous and 12 to 20 in. long. The flowering stems are erect and extend above the vegetative branches.

Mountain big sagebrush is the predominant sagebrush type in the central Rocky Mountains, forming extensive stands of uniform size at elevations of 6,000 to 10,000 ft. It also occurs on well-watered swales and pockets of deep soil at lower elevations. Soils are deep, loose, and moist, with numerous angular rocks.

Mountain big sagebrush communities are the most productive of all the big sagebrush sites. Herbaceous understory is diverse with numerous perennial forbs and high grass production. Mountain big sagebrush communities have more potential for increasing canopy cover than any other sagebrush species. Because it occupies deep, well-watered soils, grass production can be increased by reducing sagebrush canopy cover to below 25%. Therefore, depending upon the management objective, it may be desirable to reduce the canopy cover of mountain big sagebrush periodically.

Like basin big sagebrush, this subspecies is of little forage value to either livestock or big game except under the most severe winter conditions. However it often occurs intermixed with stands of bitterbrush which is a highly sought and nutritious browse species by big game. When mountain big sagebrush occurs in common with bitterbrush it provides cover and diversifies the diet of big game. In locations where snow accumulation is heavy it may become unavailable for

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big game during winter. In much of southern Idaho mountain big sagebrush communities are important late brood rearing habitat for sage grouse.

Threetip sagebrush (A. tripartite) is a round, evergreen shrub up to 3.5 ft. tall. It may have a simple, trunk-like stem or several, lesser stems arising from the base. The bark on young branches is canescent but becomes shredded and grayish, light brown to dark brown or black, on older stems. This species can layer and resprout after fire or herbicide treatment. Leaves on vegetative branches are canescent, and typically deeply divided into three linear or narrowly linear lanceolate lobes, which in turn may be three-cleft. Upper leaves are often entire.

The taxon includes two subspecies: A. tripartita ssp. tripartita and A. t. ssp. rubicola. Subspecies tripartita, also known as tall threetip sagebrush, is a freely-branching shrub up to 3.5 ft. high and is usually found as a sub-dominant shrub in Wyoming or mountain big sagebrush communities. It can layer when conditions are conducive, but it is seldom found layering in the field. It will stump-sprout after fire. Therefore, although it is a natural component of big sagebrush communities it occurs at a low frequency. However, it can become the dominant sagebrush species after repeated fires, chemical, or mowing treatments.

Subspecies rubicola, also known as Wyoming threetip sagebrush, is a dwarf shrub usually less than 6 in. tall with decumbent branches. It layers frequently and may have a crown diameter of 12 to 20 in. Leaves on vegetative branches are often deeply divided into linear lobes, each at least 1 mm wide. It can occurs on foothills as nearly solid stands or intermixed with low sagebrush. Soils are shallow, dry, and gravelly.

Threetip sagebrush often grows intermixed with other sagebrush species, but also as separate stands, with mountain big sagebrush, Wyoming big sagebrush, or alkali sagebrush. Wyoming threetip sagebrush grows on gravelly knolls at high elevations adjacent to mountain big sagebrush sites.

Three-tip sagebrush does not appear to be very palatable for either livestock or wildlife. It tends to be more deciduous that other sagebrushes losing many of its leaves in early winter. Understory vegetation of three-tip sagebrush is the same as that under the big sagebrush species that it occurs in. Wyoming three-tip sagebrush grows on shallow sites of low productive ability.

Low sagebrush (A. arbuscula) is a short, spreading, irregularly-branched shrub up to 20 in. high. Twigs are slender and densely canescent (silvery white pubescence) but may become nearly glabrous, and thus darker green, in late summer. Flower stalks persist over winter. It generally occurs in very open stands with sparse herbaceous understory vegetation.

Low sagebrush is adapted to dry, sterile, often gravelly and alkaline clay soils. Mean annual precipitation throughout its range can vary between 9.5 and 27.5 in. Seedlings develop rootsquickly to reduce the effects of soil surface drought stress. With few exceptions, soils that support low sagebrush communities feature either a dense clay “B” horizon lose to the surface, or high volumes of gravel throughout the profile. Although shallow soils tend to become waterlogged in the spring, both they and the gravelly soils have low moisture capacity and tend to become very dry by midsummer. Thus extreme droughtiness may be the dominant factor in

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low sagebrush distribution. In eastern Idaho it is found on the glacial and Pleistocene gravels in the mountain valleys. Typical low sagebrush habitat is drier and rockier than that of big sagebrush. It can, however, grow in mosaics with big sagebrush where each species is confined to a particular soil type. Low sagebrush rarely grows in mixed stands with black sagebrush. In areas where the distributions of these two overlap, low sagebrush usually inhabits sites that have more moisture or are at higher elevations than black sagebrush.

The occurrence of low sagebrush on harsh, unproductive sites makes control efforts unpromising. Most low sagebrush sites are not suited to improvement through cultivation or reseeding. Although the shrub is susceptible to fire and herbicides, the lack of site productivity rules out these managements options. Even wildfires are infrequent in the low sagebrush type due to lack of fuel. Low sagebrush flower stalks are highly sought after and an important food source for pronghorn and sage grouse during fall, winter and early spring when other vegetation is dry and dormant.

Black sagebrush (A. nova) is a small aromatic shrub generally 6 to 12 in. tall, although it may occasionally exceed 30 in. A dull grayish tomentose layer causes most populations of black sagebrush to appear darker than those of big sagebrush or low sagebrush. When the leaves of black sagebrush are crushed during the growing season there will be a sticky feel between the finger and thumb. Branches are numerous and erect and arise from a spreading base. Flower stalks are persistent throughout the winter. Populations can be found from California and Oregon in the west, to Colorado in the east, and from Montana in the north to northern Arizona and New Mexico in the south. Black sagebrush is most common at elevations ranging from 5,000 to 8,000 ft. elevation.

Black sagebrush is well adapted to dry stony soils that are relatively shallow. Root restricting layers occur at 11 to 28 in. Gravelly or sandy loam strata are also common subsurface soil profile characteristics in areas with black sagebrush. In addition, most soils supporting black sagebrush are calcareous. Black sagebrush is not restricted to adverse environments, however. If seeded, it can grow well on sites normally occupied by big sagebrush. Mean annual precipitation throughout the natural range of black sagebrush is between 7 and 13 in.

Black sagebrush can sometimes be found in almost pure stands where the soil is shallow e.g. on ridgetops and on glaciated alluvial fans. In our area, it is also frequently found in small patches and isolated plants intermixed with Wyoming big sagebrush and mountain big sagebrush stands.

Black sagebrush canopy cover is low with much bare ground. Herbaceous understory diversity and production is also low because of the dry, shallow, gravelly sites that it occurs on. Black sagebrush sites that have not been heavily disturbed have good soil biological crusts.

The flower stalks of black sagebrush are highly sought after by pronghorn and sage grouse during winter and early spring unless the plants are covered by snow.

Pygmy sagebrush (A. pygmaea) is a dwarf, depressed, evergreen, cushion-like shrub less than 8 in. tall. Bark on older stems becomes dark brown and fibrous with age. Bark on younger branches is nearly white to straw-colored and somewhat puberulent. Leaves on vegetative stems

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are green, nearly glabrous, viscidulous, and are pinnatified with three to 11 lobes, or sometimes may be toothed.

Pygmy sagebrush grows on calcareous desert soils. Mean annual precipitation within its range is approximately 8 to 12 in. In Nevada, this species is often associated with halophytic threadleaf rubber rabbitbrush (Chrysothamnus nauseosus). In Idaho it is often intermixed with black sagebrush.

Pygmy sagebrush provides little browse because of its scarcity and size. It is readily eaten, however, when available. It is a good candidate to plant in clay soils and may be of considerable value for revegetating mine spoils and roadway disturbances.

Although it is not abundant, pygmy sagebrush does provide important soil cover in dry, alkaline habitats where little else grows. It also adds to the overall biological diversity of shrub communities where it is found. Herbaceous understory vegetation is sparse.

Alkali sagebrush (A. longiloba) also known as early sagebrush and low sagebrush, is a small shrub up to 18 in. tall. It has lax, spreading stems that frequently layer. The bark is dark brown to black on older stems. The whole plant has a dark gray-green appearance. Leaves on vegetative stems are broadly cuneate, and deeply three-lobed. New growth starts in May, young heads appear in June with seed ripening in July and August.

Alkali sagebrush is found along foothills and basins of the ranges that form the Continental Divide in southwestern Montana, south through Wyoming to northwestern Colorado, and scattered westward through northern Utah and Idaho to Nevada and Oregon.

Alkali sagebrush is adapted to tight-heavy soils often in the vicinity of mountain foothills and can often also be found on neutral soils. Alkali sagebrush is characteristic of heavy highly impermeable soils, derived from highly alkaline shale’s. It is well adapted to xeric conditions. Mean annual precipitation throughout its range can vary between 8.5 and 20 in.

Alkali sagebrush, depending on location and ecotype, can be a source of palatable browse for domestic sheep and provide habitat and forage for other animals. Stands of alkali sagebrush in good condition can support a diverse understory of perennial grasses and annual and perennial forbs. Such stands provide forage and cover for sage grouse, pronghorn, other wildlife, and domestic livestock. Some stands, however, are much less diverse and provide little forage or habitat. Sites that lack a satisfactory understory remain closed unless shrubs are reduced by fire or other disturbance. Decadent stands can be rejuvenated by mechanical means. This shrub has the potential to be a useful plant in rehabilitation, especially on heavy, seasonally dry soils.

Fringed sage (A. frigida) also known as prairie sagewort, fringed sagewort and fringed sagebrush, is an aromatic, mat-forming, perennial shrub 8 to 24 in. tall. The lower woody stems are spreading and often branched, while upper herbaceous stems are erect and leafy. Adventitious roots may occur when stems come in contact with soil. The entire plant is densely silver canescent.

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Fringed sage in the Intermountain area extends from 3,000 to 6,000 ft.; in other parts of its range the lower elevational limits are somewhat less. Mean annual precipitation throughout the native range of fringed sage varies between 8 and 22 in. It inhabits a wide variety of sites but typically grows in full sunlight on dry, coarse, shallow soils intermixed with other sagebrush species.

Mountain silver sagebrush (A. cana ssp viscidula) is an erect shrub usually not more than 3.5 ft. tall. It is distinguished from plains silver sagebrush (A. c. ssp. cana) by its smaller, darker leaves, and more western distribution. Leaves on vegetative stems are typically simple, entire, and grow in dark green clusters. This subspecies varies in appearance but is always darker than mountain big sagebrush, with which it is often growing. It can be difficult to control because of its tendency to resprout from the crown and to spread by rhizomes. It is not as susceptible to fire as other species of sagebrush. Silver sagebrush mortality after prescribed fall and spring burns is directly related to fire intensity. In general, fall burns are more effective at reducing silver sagebrush than spring burns.

Mountain silver sagebrush is found in mountain meadows and borders of aspen stands throughout the Rocky Mountains at elevations of 6,000 to 10,000 feet. In eastern Idaho it can usually be found along mountain streams and mountain meadows with heavy snowpack. Soils are normally deep, rich loam. Because of the deep, rich soil and abundant moisture, understory herbaceous vegetation is usually diverse and abundant. However. If the site is heavily grazed the streams usually become down-cut and the sites dry out reducing the sagebrush overstory and producing an understory dominated by Kentucky bluegrass (Poa pretense) or Canada bluegrass (P. compressa).

Budsage (A. spinescens) also known as spring sage and bud sagebrush, is a low, spinescent, pungently aromatic, rounded shrub 4 to 20 in. high and profusely branched at the base. Young branches and leaves are covered with a white-tomentose pubescence that becomes stiff and gray with age. Unlike most members of the genus, budsage is deciduous, losing most leaves by midsummer. Budsage is well adapted to xeric conditions. It is quite common in semiarid valley bottoms, benches, and foothills throughout the Interior western United States. It is found in southwestern Idaho salt-desert areas. Mean annual precipitation throughout its habitat varies between 6 and 10 in. It has an extensive root system that grows primarily within the top 6 to 21 in. of the soil. Summer dormancy is an adaptation that reduces the effects of drought stress. Early in the spring, when budsage first shows signs of breaking dormancy and prior to bud elongation, the previous season’s bark growth can be removed easily. Shrubs subsequently produce new, bright-green leaves as soon as February or March. Terminal and lateral buds generally expand and begin to elongate in late March and early April. Although budsage ordinarily begins to grow in early spring and becomes dormant by midsummer, it occasionally may break summer dormancy after late summer storms.

Budsage is a palatable, nutritious winter forage for upland birds, small game, big game, and domestic sheep. It is particularly preferred just after dormancy. Budsage is high in calcium, magnesium, phosphorous, and protein. It is usually more palatable in late winter than early winter. Palatability again decreases once twigs have elongated and volatile oil content increases.

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Budsage is especially important to grazing animals during late winter in areas where there is an abundance of dry grass. Unfortunately, it does not tolerate grazing well, and continual heavy grazing may eliminate it from certain areas. In order to maintain the species in plant communities, periodic rest from grazing is needed. This allows seed and seedlings to develop.

Budsage is an important native shrub because of its forage value to various species of wildlife and domestic livestock. Wildlife species that utilize budsage include mule deer, pronghorn, mountain sheep, black-tailed jackrabbits, and chucker partridge. In areas of local abundance, budsage can be an important source of protein during late winter months.

Classification and Condition of Sagebrush Ecosystems

The need to classify plant communities and land units has long been recognized by natural resource managers, resulting in the development and use of different classification systems. Unfortunately, such classifications have stressed current site occupancy and identity by a few commercially important plants. Little consideration has been given to the successional status of the existing plant community or to potential productivity of the environment as reflected by the climax plant community.

Over the years three different land/plant community classification schemes were developed to describe the ecological potential and present condition of the plant community. The range site classification is based on both the potential of the site and the present plant community relative to potential climax plant community. Thus the productivity of the site is included in the classification and present condition relative to the potential climax plant community. Habitat type classification is based on the present plant community relative to the potential climax plant community. Unlike range site the habitat type classification does not include the potential productive capability of the site. The third plant community classification, community type, only describes the current plant community and does not try to predict the climax plant community or the potential productivity of the site. Thus, it is able to handle disturbed plant communities.

The range site [also called Ecological Site] classification developed by Dyksterhuis [1949] was adopted by the Soil Conservation Service [now Natural Resource Conservation Service (NRCS)], and by the Bureau of Land Management, was the first attempt at classifying sagebrush steppe plant communities. Although the basis of this classification is the climax plant community, emphasis is placed on site productivity, and nomenclature is descriptive of site and plant community.

A few years after Dyksterhuis developed the range site classification Daubenmire [1952] developed the habitat type concept of classification. The habitat type concept gained increasing acceptance, particularly by the Forest Service. This system stresses the use of the entire climax plant community as an environmental integrator, permitting identification of habitats with similar biotic potentials. Consequently, a particular habitat type has the potential for supporting the same climax plant community regardless of the plant community that presently occupies the area. Although vegetation is primarily used to identify and characterize the habitat type, knowledge of soil relations is important, especially where the original plant community has been altered by

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grazing, fire, or other manipulations. However, different soils may be capable of supporting the same climax plant community, but with varying levels of productivity.

The habitat type is generally named after the unique combination of dominants in the overstory and understory. Factors other than the climax plant community may be used to delineate areas of similar potential, but they are not usually as satisfactory for assessment of comparable environments. Climax plant communities reflect the environment and provide a means of recognizing similar areas. Although soils and other factors are also useful in classification, the plant community is most easily observed and is the basic resource being directly managed. A binomial nomenclature system is usually adequate, but sometimes a trinomial is necessary.

In the early 1970’s Mueller-Dombois and Ellenberg developed the community type classification. Community type is a classification based on the present plant community and does not try to interpret the successional stage of the community, the ecological potential of the site, or the potential productivity of the site.

Both the range site classification and the habitat type classification systems imply that when a sagebrush steppe plant community is disturbed it will go through successional stages, or seres, and eventually, with proper management, return to the original [climax] plant community and productivity. These classification schemes represent classic plant community ecology [called synecology] dynamics and rely on the fact that a plant community that has been disturbed will eventually return to its original [climax] condition. However, field observations have determined that some sagebrush steppe plant communities do not seem to return to the original [climax] plant community after disturbance irrespective of how it was managed. As an example, sagebrush steppe communities in the Great Basin where cheatgrass becomes established never return to a native perennial grass-forb herbaceous understory. The vegetative productivity of the site also remains much lower than prior to the disturbance.

Studies in North America as well as studies of other steppes, especially in the Middle East and Asia have determined that brushland steppe vegetation does not always follow classic synecology dynamics. Although the range site classification and habitat type classification is still used by management agencies there is becoming a common acceptance that it is not adequate for all management objectives.

Range Condition and Trend

In addition to ecological site classifications there are two other ways frequently used to describe the present condition of rangelands. These are range condition and range trend.

Range condition or health is the status of vegetal cover and soil in relation to a standard or ideal for a particular habitat type or site. Trend is change in condition. Condition and trend are recognizable by certain indicators that can be seen in soil and vegetation. These indicators help to interpret past and current changes in the plant ecosystem, and often suggest what may be expected in the future.

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Reliable judgment of condition and trend is essential to effective evaluation of the success or failure of range management practices. Consequently, the range manager must be able to identifythe plants and habitat types or sites, to understand ecological principles including patterns of and reasons for change, and to properly interpret change as a basis for needed adjustment inmanagement prescriptions.

Soil stability is an essential requirement of satisfactory condition. In other words, plant cover must be sufficient to protect the soil from accelerated erosion. Besides quantity of vegetation,quality is important and is usually satisfied by a mixture of perennial grasses and forbs.

Judgment of range condition usually must be made in relation to pristine. For the most part, the best approximation is a relic area that has never been grazed by livestock or otherwise disturbed.However, this does not mean that pristine condition is the management objective. It serves only as a guide to indicate what quality and quantity of vegetation the area is capable of supporting, character of the litter cover, and normal appearance of the surface soil. Comparisons can be made only between ranges of similar potential, therefore, judgment of condition should be preceded by classification of range ecosystems into habitat types or range sites.

Fluctuations in weather must be accepted as normal events whose effects must be considered when judging range condition. Variations in amount of precipitation and patterns of distributiongreatly affect plant development and yield, but their influence on soil stability is usually minor.

Trend may result from some degree of change in any component of the plant community. For practical purposes, however, only soil and vegetation need be considered in assessment of trend, which is simply the recognition of the nature, rapidity, and direction of ecological change. In determining trend, one must distinguish between those cumulative changes that produce a real difference in condition and those that are mere fluctuations. For example, a large crop of seedlings of desirable perennial species may reflect only a temporarily favorable combination of circumstances. A surer indication of upward trend would be plants of successively older age classes in addition to the seedlings. Important indicators of range condition and trend includecover, bare soil surface, observed movement of soil, trampling displacement, soil remnants, erosion pavement, lichen lines, active gullies, wind-scoured depressions, aeolian deposits, alluvial deposits, vegetal composition, age classes, annual weeds, invasion of bared surfaces, vegetation in gullies, rill-channel ridges, accessibility of palatable species, relics, hedged shrubs, and current utilization. These indicators provide clues to events that have happened, are happening, or will happen on the range watershed.

Below are some general guides used for recognizing condition and trend in southern Idaho. These can be broadly used by a manager to make reasonable judgments of range condition and trend for a variety of habitat types or sites, especially those at intermediate and low elevations.

1. Sagebrush with a good understory of native perennial grasses and forbs. Such ranges have not been greatly changed from their original condition, and forage production is not far below the potential. The understory is composed of native perennial grasses and forbs, which make up more than a third of the total vegetation and are abundant in the spaces between sagebrush

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plants. However, they usually do not form a solid cover and some bare ground can be expected. Sagebrush is in open stands. Soils are essentially unchanged from their original condition,with no observable erosion. Condition is classed as good or excellent.

2. Sagebrush with a sparse understory of native perennial grasses. On these ranges native perennial grasses have been reduced to a scattered stand, sagebrush may have thickened, and native perennial forbs are virtually lacking. Erosion is often severe, but on level sites soil may be in relatively good condition because of protection by the dense sagebrush cover. Forage production is light and mostly unavailable to grazing animals. Range condition is poor to fair.

3. Sagebrush with an understory of annual grasses and weeds. These ranges may be characterized by a dense stand of sagebrush with an understory of annuals. Native perennial grasses are present only as scattered individuals. Severe erosion has often occurred as indicated by erosion pavement or pedestaled plants. On level ground, however, the soil surface may be rather well preserved even though the forage cover is depleted. The already poor forage production is unstable in quantity from year to year. Range condition is classed as very poor to poor.

4. Ranges with sagebrush replaced by cheatgrass or other annuals. Ranges on which sagebrush and other original species have been destroyed by recurrent fires, cultivation, or grazing, nowsupport nearly pure stands of annual grasses or weeds. Soil losses are often severe; however, soil condition of some cheatgrass ranges may be good. Although forage production on such rangescan be high, it is highly variable and may be extremely low in years of scanty precipitation.

Knowledge of trend is essential in planning and evaluating a grazing program. For each of the four categories described above, trend in condition is shown by distinct plant or soil indicators.With the exception of accelerated erosion, a single indicator is seldom sufficient to depict trend. Although a careful inspection may reveal apparent trend, observation of indicators over a series of years may be necessary for definite confirmation.

1. Sagebrush with a good understory of perennial grasses and forbs.

Improvement or maintenance of ranges already in satisfactory condition will be accompanied by few or no indicators of trend. Palatable grasses and forbs should be vigorous, and a fewseedlings may be in the process of becoming established. Few sagebrush seedlings are evident, and soil is stable.

Indicators of downward trend in order of occurrence include a decrease in vigor of palatable perennial forbs and the fine grasses, increase in number and size of annuals, decrease in vigor of the robust perennial bunchgrasses, establishment of numerous young sagebrush plants in the openings, death of parts of perennial forb and grass clumps, and excessive pedestaling of bunchgrasses.

2. Sagebrush with a sparse understory of perennial grasses.

Upward trend is indicated by increase in vigor of native perennial grasses and forbs and establishment of a few seedlings. Although a few sagebrush seedlings may be present,

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production of sagebrush usually declines as a result of loss in vigor of established plants. There should be a slight accumulation of litter and less prominent pedestaling of bunchgrasses.

Downward trend is indicated by an increase in sagebrush and annuals such as cheatgrass. Such changes are accompanied by a decrease in palatable perennial grasses and forbs and establishment of young sagebrush plants in the openings.

3. Sagebrush with an understory of annuals or range with sagebrush replaced by annuals.

Natural improvement of vegetation on such areas will usually be extremely slow; consequently, upward trend must be judged primarily by increase in litter and stabilization of the soil. Establishment of a few seedlings of native perennial grasses and forbs may occur.

Downward trend may be indicated by low vigor of annuals, replacement of cheatgrass by weeds, and by active gully and wind erosion.

Although the above indicators of condition and trend generally apply to sagebrush-grass vegetation, they have only limited value in habitat types dominated by such palatable species as black sagebrush.

Upward trend is indicated by an increase in black sagebrush and palatable perennial grasses such as Indian ricegrass, whereas a decrease in these species, along with an increase in such unpalatable species as small rabbitbrush, denotes a downward trend.

Special situations must be recognized and evaluated by different standards. For example, a depleted area of sagebrush-grass range that has been satisfactorily revegetated with desirableexotic species can be considered to be in good condition provided soil is stable and yield of vegetation is near potential for the site and in line with management objectives. These may be considerably different from those of native sagebrush-grass range. Condition and trend for the most part are considered in relation to natural vegetation and deviations therefrom. Condition and trend of sagebrush-grass ranges cannot be adequately evaluated without an examination of included riparian and aquatic areas, which may be particularly sensitive indicators of what is happening on the range as a whole. Not only do livestock tend to concentrate in such areas and have serious direct impacts on vegetation, soil, and water quality, but these areas can also be severely damaged by runoff and erosion from surrounding poor condition range.

Other factors to consider when evaluating range condition:

1. Noxious Weeds—These are plants that are designated as noxious weeds by the Secretary of Agriculture or by an appropriate State official. Noxious weeds generally possess one or more of the following characteristics: aggressive and difficult to manage, poisonous, toxic, parasitic, invasive, and new or not common to the United States. Data collection focuses on determining the presence or absence of a noxious weed. If any noxious weed is found on a sample site the acres represented by that sample are determined to be at risk from both a health and sustainability viewpoint, even if the ground cover is adequate for a properly functioning

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watershed. This interpretation is made because of the aggressive nature of noxious weeds in both pristine and disturbed landscapes.

2. Ground Cover—A stable and sustainable soil base is needed for rangeland watersheds to yield a variety of multiple-use products, services, and amenities. The soil base, no matter what the soil classification, needs an adequate ground cover of vegetation, litter, and rock for protection from rain, erosion, and use. Qualitative rangeland health and functionality checklists in the literature have a majority of indicators and descriptors focusing on various aspects of ground cover. Indicators deal with some aspect of a lack ground cover protection, such as rills, water flow patterns, bare ground, soil surface resistance to erosion, and litter amount. Using a broad-scale vegetation classification base, ground cover threshold levels are developed to represent the threshold point at which a site in a particular cover type would begin to lose basic functionality defined by increased soil erosion and loss of site sustainability. Ground cover is defined as basal vegetation, litter, moss/lichen, or rock greater than 3⁄4-inch diameter.

3. Species Composition—Determining if the proper vegetation is present on a site is the mostdifficult question in the rangeland health discussion. A general evaluation of ecological status may be conducted using a basic species composition list; however, species lists would probably need to be revised to adequately assess a site’s ability to meet more specific health or other management objectives.

4. Shrub Cover—Many rangelands across the United States have a major shrub component. Because of ecological processes such as fire, insects and disease, and normal life cycles, sagebrush ecosystems naturally have a broad range of self-sustaining communities with a variety of age classes and structures. Such a mix of components provides a variety of habitat and food that benefit an assortment of wildlife and domestic animals, along with a diversity of visual and watershed aspects across the landscape.

States, Transitions, and Disturbances

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Other Ecosystem Concerns

All of the above measures to identify the present condition of plant communities relative to their potential climax composition and productivity only consider the plant communities themselves. None include consideration for native vertebrate or invertebrate species, or the impact of habitat fragmentation resulting from infrastructure (roads, railroads, utility corridors, energy development, etc.) development. Therefore, none of the classifications systems used today are truly ecosystem classification systems.

Some concluding thoughts

Patterns of disturbance and recovery function to shape the composition, structure, and integrity of all ecosystems, including shrublands, and are strongly influenced by both natural (for example, climate) and human (for example, livestock husbandry) controls. Although these processes vary naturally, rapid or persistent change in either disturbance regimes or successional pathways may result in a loss of ecosystem functionality or resiliency and subsequently result in ecosystem degradation.

Humans affect shrublands by altering natural disturbance regimes, creating new disturbances processes, and by altering succession. Human activities produce both intended and unintended consequences. Over time, the nature and magnitude of human-caused impacts on shrublands reflect changes in the values associated with shrub-dominated landscapes and the capacity of evolving cultural systems and associated technologies to enact change. Impacts have been significant and often severe in regions of the world where human activities have been both intense and persistent over long time periods. For example, the results of long-term degradation of arid and semiarid shrublands, woodlands, and forests in Iran can be compared to the recent and relatively low levels of degradation in the arid and semiarid ecosystems of western North America’s Great Basin. The potential for severe degradation not unlike that found in Iran and in similar old-world environments if management and use of this region do not reflect a stronger conservation ethic than that observed from extraction-based economies introduced by Euro-American settlers in the 19th century.

Worldwide, shrub-dominated ecosystems are increasingly at risk of degradation and loss as human-related impacts increase and natural patterns of disturbance and recovery are truncated due to the cumulative and interacting impacts of changing climate, CO2 fertilization, altered fire regimes, invasive species introductions, fragmentation and conversion. The shrublands of western North America are no exception. Proactive measures to curtail losses of functional shrubland ecosystems must include the development of scientifically sound strategies and practices for restoration and rehabilitation. Of necessity, the development and application of these strategies and practices will require adaptive approaches as paradigms shift in an ever changing world.

To further belabor the many ills of the sagebrush ecosystem is to ignore the real question of importance. And that is, what can be done to improve the situation? In addressing this question,

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The system [ecosystem] flourishes only when each element – the lichen, the oak, the squirrel or moose, the hawk or wolf, and the human being – plays its appropriate part.

− Aldo Leopold

two primary objectives are likely to drive future management of sagebrush steppe ecosystems: (1) the desire to maintain current sagebrush habitats and associated flora and fauna; and (2) the desire to restore at least a portion of sagebrush

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