Approximately 86 percent of BLM-administered surface in the Planning Area is characterized as sagebrush shrub habitat, foothill mountain sage and shrub, and desert salt shrub and greasewood.
Livestock grazing, fire, fire suppression, and to a lesser extent surface-disturbing activities, have influenced many grassland/shrub vegetative types in the Planning Area. Invasive species have encroached into many plant communities. Refer to Section 3.6.7 Livestock Grazing, Section 3.3 Fire and Fuels Management, and Section 3.4.4 Invasive Species for additional information.
The broad scale Wyoming GAP analysis data are used in this analysis, as this data is appropriate for regional and large area planning efforts. Actual on-the-ground management is conducted using ecological site descriptions developed by the Natural Resources Conservation Service (NRCS), of which there are more than 60 for the Planning Area.
Grasslands, which include lowland, foothill, mountain, and alpine types, cover approximately 67,675 acres of BLM-administered land and 155,877 acres of all federal mineral estate in the Planning Area (2.1 percent of all BLM-administered surface land or 3.7 percent of all federal mineral estate). Most of the grassland areas are in valley bottoms, uppermost south-facing slopes, and scattered patches on windswept ridges. Grasslands are split into four plant communities mixed grass prairie, Great Basin foothills grassland, meadow tundra, and subalpine meadow as described below.
Mixed grass prairie contains a mixture of short grass and tall grass prairie species. Vegetation can contain or be dominated by silver sagebrush; trees and shrubs cannot occupy more than 25 percent of the total cover. Mixed grass prairie provides habitat for sensitive species such as the mountain plover, Baird’s sparrow, long-billed curlew, black-footed ferret, white-tailed prairie dog, and various bat species. Typical ecological sites found in the mixed grass prairie plant community include Overland Flow 10- to 14-inch precipitation zone and Overland Flow 15- to 19-inch precipitation zone.
Great Basin foothills grassland is a mesic grass-forb mixture found in the foothills of northwestern Wyoming. There may be an important lupine or arrowleaf balsamroot component found in this type of grassland. This community provides habitat for sensitive species such as the mountain plover, Baird’s sparrow, long-billed curlew, black-footed ferret, white-tailed prairie dog, and various bat species. Typical ecological sites found in the Great Basin foothill grassland plant community include Loamy 15- to 19-inch precipitation zone and Shallow Loamy 15- to 19-inch precipitation zone.
Meadow tundra includes graminoid- and forb-dominated vegetation that occurs above the upper tree line (approximately 9,800 feet amsl) in the alpine zone. Common species in this vegetation type include bent grasses, sheep fescue, icegrass, and alpine mosses. This community provides habitat for sensitive species such as the greater sage-grouse and various species of neotropical migratory birds. Typical ecological sites in the meadow tundra plant community include Course Upland 15- to 19-inch precipitation zone and Very Shallow 20+-inch precipitation zone.
Subalpine meadow occurs between an elevation of about 4,700 feet and 9,800 feet amsl. It is characterized and dominated by graminoids and forbs. Typical ecological sites in the subalpine meadow tundra plant community include Wetland 10 to 14 inch precipitation zone and Wetland 15- to 19-inch precipitation zone. This community provides habitat for sensitive species such as the greater sage‐grouse and various species of neotropical migratory birds.
Shrublands dominate the Planning Area, representing approximately 2,690,284 acres of BLM-administered land and 3,341,608 acres of federal mineral estate (84.3 percent of all BLM-administered surface land or 79.4 percent of all federal mineral estate). These communities are generally diverse in plant composition and provide important forage and cover for wildlife and livestock. Shrublands are split into seven plant communities mesic upland shrub, xeric upland shrub, mountain big sagebrush, Wyoming big sagebrush, desert shrub, saltbush fans and flats, and greasewood fans and flats as described below.
This vegetation type includes a variety of shrub communities that grow in relatively mesic sites (often snow catchments or in ravines). Most often, Rocky Mountain maple, bigtooth maples, snowberry, wax currant, or chokecherry are the dominant shrub species. Typical ecological sites in the mesic upland shrub plant community include Course Upland 20+-inch precipitation zone.
Xeric upland shrub is a shrub cover dominated by species of curlleaf mountain mahogany. This community provides habitat for many species, including various bat, raptor, and mammal species. Typical ecological sites in the xeric upland shrub plant community include Steep Loamy 20+-inch precipitation zone.
This shrub type is dominated by mountain big sagebrush often found mixed with grasses. This community provides habitat for sensitive species, including the greater sage-grouse and other sagebrush obligate species. Typical ecological sites in the mountain big sagebrush plant community include Loamy 10- to 14-inch precipitation zone, Shallow Loamy 10- to 14-inch precipitation zone, Sandy 10- to 14-inch precipitation zone, Shallow Sandy 10- to 14-inch precipitation zone, Clayey 10- to 14-inch precipitation zone, and Shallow Clayey 10- to 14-inch precipitation zone.
This vegetation type is a shrub steppe type dominated by Wyoming big sagebrush. This vegetation type can vary from dense, homogeneous Wyoming big sagebrush to sparsely vegetated arid areas where Wyoming big sagebrush is the dominant shrub. This community provides habitat for sensitive species, including the Brewer’s sparrow, loggerhead shrike, sage thrasher, ferruginous hawk, and the greater sage-grouse. Typical ecological sites in the Wyoming big sagebrush plant community include Loamy 5- to 9-inch precipitation zone, Shallow Loamy 5- to 9-inch precipitation zone, Sandy 5- to 9-inch precipitation zone, Shallow Sandy 5- to 9-inch precipitation zone, Clayey 5- to 9-inch precipitation zone, and Gravelly 5- to 9-inch precipitation zone.
This vegetation type consists of a mixture of shrubs occurring in dry, saline habitats. Shrubs in this vegetation type are often dominated by shadscale saltbush, but can also be a mixture of Gardner’s saltbush, black greasewood, and desert cushion plants. This community provides habitat for sensitive species, including the greater sage-grouse, Brewer’s sparrow, loggerhead shrike, sage thrasher, and ferruginous hawk. Typical ecological sites in the desert shrub plant community include Saline Upland 5- to 9-inch precipitation zone, Saline Upland 10- to 14-inch precipitation zone, Shale 5- to 9-inch precipitation zone, and Shale 10- to 14-inch precipitation zone.
This vegetation type consists of areas where Gardner’s saltbush comprise more than 75 percent of the vegetative cover. These relatively pure saltbush stands are often sparsely vegetated, with bare soil constituting most of the land surface. This community provides habitat for sensitive species, including mountain plover, greater sage-grouse, long-billed curlew, ferruginous hawk, loggerhead shrike, Brewer’s sparrow, and burrowing owl. Typical ecological sites in the saltbush fans and flats community include Saline Upland 5- to 9-inch precipitation zone and Saline Upland 10- to 14-inch precipitation zone.
This vegetation type consists of areas where greasewood comprises more than 75 percent of the total shrub cover and shrubs comprise more than 25 percent of the total vegetative cover. This community provides habitat for sensitive species, including Brewer’s sparrow, loggerhead shrike, sage thrasher, and ferruginous hawk. Typical ecological sites in the greasewood fans and flats plant community include Saline Lowland 5- to 9-inch precipitation zone and Saline Lowland 10- to 14-inch precipitation zone.
Common indicators of rangeland health include organic ground cover (live and dead), plant species composition and diversity, bare ground, litter, and the presence and density of noxious weed species. These indicators are associated with Standards 1, 3, and 4 of the Wyoming Standards for Healthy Rangelands (Appendix N).
The presence of noxious weeds and other invasive species might indicate a disturbance to the native plant community. Denser populations of invasive species are generally associated with areas that have been affected by surface-disturbing activities, wildfire, changes in water regime, or other major events. The presence and accelerating rate of spread of undesirable plants is a threat that could reduce the ability of vegetation to continue providing desired levels of products and services.
Indicators of rangeland health described in Technical Reference 1734-6, Interpreting Indicators of Rangeland Health include soil surface resistance to erosion and soil loss or degradation (including soil compaction); plant community composition and distribution in relation to infiltration and runoff; functional/structural groups; ratio of plant mortality/decadence to young or mature individuals in the community; amount of litter; annual production; invasive plants; and reproductive capability of perennial plants (BLM 2005e).
Fire suppression, historic livestock grazing practices, and road development have disrupted fire return intervals in the sagebrush/grassland plant communities. As a result, there has been an increase in juniper density with a corresponding decrease in perennial bunch grasses and forbs, and in some areas a loss of age class and structural diversity. In recent years, invasive species, particularly nonnative bromes, have increased greatly in the Planning Area. Many areas in the sagebrush/grassland community that have experienced multiple wildfires have been converted to cheatgrass monocultures.
Since the completion of the Cody, Grass Creek, and Washakie RMPs, approximately 423 projects and 82,314 acres of vegetation treatments have been initiated in the Planning Area (see Section 3.6.7 Livestock Grazing Management) to address changes in vegetative condition (BLM 2009b). Vegetation treatments are currently implemented under the principles and methodology in Instruction Memorandum (IM) 2008-030 (BLM 2007c), which gives guidance to BLM field offices on implementing the Record of Decision (ROD) for the National Vegetation Treatments Final Programmatic EIS (BLM 2007a) and Programmatic Environmental Report.
Grassland and shrubland vegetative communities are subject to the influences of wildfire and prescribed fire. Title 1 of the Healthy Forest Restoration Act of 2003 requires identification and mapping of the fire regimes and FRCC on BLM-administered lands at risk of wildfire and insect or disease epidemics. See Section 3.3 Fire and Fuels Management for more discussion on FRCC as it relates to vegetation.
In the Planning Area, the BLM is implementing the Wyoming Reclamation Policy (BLM 2009l), which identifies ten reclamation requirements, of which restoring a disturbed site to sound ecological health and controlling invasive species are priorities.
Invasive plant species can dramatically affect native plant communities and disrupt the functions of native ecosystems. Nonnative bromes have expanded their range throughout the Planning Area due largely to increased fire frequency. If they are allowed to proliferate, invasive plant species and noxious weeds have the potential to negate any existing or future improvement in vegetation resources. If future circumstances result in a net loss of productive vegetation, the present supply of vegetation and kinds of goods and services vegetation provides society will not be sustainable (refer to Section 3.3.4 Invasive Species and Pest Management).
The loss of soil through wind and water erosion can remove valuable nutrients and organic matter from the ecosystem. When the rate of loss exceeds the rate of soil formation there is a net loss of soil. There is a threshold when the amount of soil loss starts to affect plant communities. This threshold varies with soil type. Once a threshold has been crossed, the plant community that could be supported on a site could change. See Section 3.1.3 Soil for more information.