This study investigated plant and soil (organic carbon, SOC) responses to shrub management in western U.S. rangeland dominated by Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young). Plants and soils were sampled in 2009 from paired sets of treatments (mowing to 10 cm height, aerial herbicide application of Spike® 20P [tebuthiuron]) in Sandy and Loamy ecological sites. Plant responses to mowing were consistent for both ecological sites with 1) no effects on live, but three- to four-fold increases in dead, Wyoming big sagebrush plant density, 2) reduced height and cover of Wyoming big sagebrush, 3) increased cover of perennial grasses, and 4) no effects on bare ground. For soils, increased SOC did occur with herbicide application in the Loamy site for both the 0-5 cm (43% increase) and 5-15 cm (17% increase) soil depths, which corresponded to annual soil C sequestration rates of 0.16 and 0.14 Mg C ha -1 yr -1 for the 0-5 and 5-15 cm soil

This research was initiated in 1997 to evaluate the effects of seeding rates of grass and Wyoming big sagebrush on the establishment of big sagebrush. The research was accomplished at the Belle Ayr West mine, south of Gillette, WY using a randomized complete block with three big sagebrush seeding rates (1, 2, and 4 kg PLS /ha) and seven grass seeding rates (0, 2, 4, 6, 8, 10, and 14 kg PLS /ha ) experimental design. Field data were collected from 1997-2004 and re- sampled in 2010 to evaluate the long-term effects of these seeding rate treatments on big sagebrush density and plant canopy volume. Wyoming big sagebrush average density decreased by 25-33 % from 2004 to 2010 but the density remained above the 1 plant/m 2 level required by regulatory standards. Wyoming big sagebrush average canopy volume in 2010 (per plant) was 15 times greater than observed in 2004. Shrub density, cover, and height met or exceeded the levels recommended for sage grouse and antelope habitat, two primary users of these lands that are a concern to wildlife management agencies and mine regulatory agencies in WY. General sage grouse requirements are 1.5 plants/m 2 , a shrub height of 18 to 26.6 cm, and shrub cover of 5.5 %. General antelope shrub height requirements are 22 to 46 cm, and cover requirements are 5 to 30 %. This emphasizes the importance of grass and sagebrush seeding rates necessary to achieve these desire goals.

Rangelands occupy approximately half of the world's land area and store greater than 10% of the terrestrial biomass carbon and up to 30% of the global soil organic carbon. Although soil carbon sequestration rates are generally low on rangelands in comparison to croplands, increases in terrestrial carbon in rangelands resulting from management can account for significant carbon sequestration given the magnitude of this land resource. Despite the significance rangelands can play in carbon sequestration, our understanding remains limited. Researchers conducted a literature review to identify sustainably management practices that conserve existing rangeland carbon pools, as well as increase or restore carbon sequestration potentials for this type of ecosystem. The research team also reviewed the impact of grazing management on rangeland carbon dynamics, which are not well understood due to heterogeneity in grassland types. The literature review on the impact of grazing showed a wide variation of results, ranging from positive to negative to no response. On further review, the intensity of grazing appears to be a major factor in controlling rangeland soil organic carbon dynamics. In 2003, researchers conducted field sampling to assess the effect of several drought years during the period 1993-2002. Results suggested that drought can significantly impact rangeland soil organic carbon (SOC) levels, and therefore, carbon sequestration. Resampling was conducted in 2006; results again suggested that climatic conditions may have overridden management effects on SOC due to the ecological lag of the severe drought of 2002. Analysis of grazing practices during this research effort suggested that there are beneficial effects of light grazing compared to heavy grazing and non-grazing with respect to increased SOC and nitrogen contents. In general, carbon storage in rangelands also increases with increased precipitation, although researchers identified threshold levels of precipitation where sequestration begins to decrease.

Wildlife browsing of Artemisia tridentata ssp. wyomingensis (big sagebrush) on reclaimed coal mined land threatens long-term, sustainable reclamation success. A wildlife-proof exclosure was constructed in 2001 on a 10-year old A. tridentata ssp. wyomingensis reestablishment research site at North Antelope Coal mine in northeastern Wyoming to assess wildlife browsing impacts. Artemisia tridentata ssp. wyomingensis survival, growth, and plant community attributes (species richness, canopy cover, and diversity) were evaluated inside and outside the exclosure, across the original grass seeding rate treatments (0, 16, 32 kg PLS ha−1). Long-term A. tridentata ssp. wyomingensis density decreased across all seeding rates from 1994 to 2002. Higher A. tridentata density, leader (shoot) growth, and canopy cover, along with lower mortality, occurred inside the exclosure across all seeding rates. Lower winter use, higher survival, and lower mortality of A. tridentata ssp. wyomingensis in the 32 compared to the 0 and 16 kg PLS ha−1 seeding rates suggest a beneficial relationship between A. tridentata ssp. wyomingensis survival and higher grass seeding rate. Approximately 33% mortality of marked A. tridentata ssp. wyomingensis plants occurred outside the exclosure. Lepus townsendii campanius (white-tailed jackrabbit), L. californicus melanotis (black-tailed jackrabbit), and Sylvilagus audubonii baileyi (cottontail rabbit) were identified as primary browsers of A. tridentata. Plant species richness, cover, and diversity decreased from 2001 to 2002, probably due to below average precipitation during the study. Defoliation of A. tridentata ssp. wyomingensis was severe, indicating the magnitude of impact from browsing wildlife. Post mining wildlife management and habitat manipulation on adjacent rangeland is suggested to ensure successful reclamation of coal mined lands.

Our aim in this study was to evaluate short-term (2 years) responses of several attributes of small mammal populations (species richness, abundance, diversity, and similarity) and plant community dynamics (species richness, canopy cover, above-ground biomass production, and diversity) to the mechanical disturbance associated with interseeding. Small mammal live trapping and vegetation sampling were conducted in 2004 and 2005 on replicated 1 ha study plots in a native Wyoming big sagebrush (Artemisia tridentata Nutt ssp. wyomingensis Beetle & Young)-grassland that were: 1) mechanically disturbed in April 2003 and rested from grazing during the study (mechanical); 2) rested from grazing (rested); and 3) moderately grazed by cattle (grazed). Deer mice (Peromyscus maniculatus), northern grasshopper mouse (Onychomys leucogaster), and sagebrush vole (Lemmiscus curtatus) were the primary small mammal species captured during 7776 trap nights in 2004 and 2005. Small mammal diversity was greater for the mechanical (H′ = 1.22) than the rested (H′ = 0.85) treatment with the grazed treatment intermediate. Plant community variables of species richness, diversity, similarity, and above-ground biomass production did not differ among treatments. Canopy cover of the dominant species, Wyoming big sagebrush, was reduced 20–34% by the mechanical disturbance (6.9% ± 1.0) compared to rested (8.6% ± 0.6) and grazed (10.4% ± 1.0) plots. The mechanical disturbance affected approximately 10.5% of the ground surface area but this had little impact on short-term small mammal or plant community dynamics in this rangeland ecosystem.

Rangelands account for almost half of the earth's land surface and may play an important role in the global carbon (C) cycle. We Studied net ecosystem exchange (NEE) of C on eight North American rangeland sites over a 6-yr period. Management practices and disturbance regimes can influence NEE; for consistency, we compared ungrazed and undisturbed rangelands including four Great Plains sites from Texas to North Dakota, two Southwestern hot desert sites in New Mexico and Arizona, and two Northwestern sagebrush steppe sites in Idaho and Oregon. We used the Bowen ratio-energy balance system for continuous measurements of energy, water vapor, and carbon dioxide (CO2) fluxes at each study site during the measurement period (1996 to 2001 for most sites). Data were processed and screened using standardized procedures, which facilitated across-location comparisons. Although almost any site could be either a sink or source for C depending on yearly weather patterns, five of the eight native rangelands typically were sinks for atmospheric CO2 during the study period. Both sagebrush steppe sites were sinks and three of four Great Plains grasslands were sinks, but the two Southwest hot desert sites were sources of C on an annual basis. Most rangelands were characterized by short periods of high C uptake (2 mo to 3 mo) and long periods of C balance or small respiratory losses of C. Weather patterns during the measurement period strongly influenced conclusions about NEE on any given rangeland site. Droughts tended to limit periods of high C uptake and thus cause even the most productive sites to become sources of C on an annual basis. Our results show that native rangelands are a potentially important terrestrial sink for atmospheric CO2, and maintaining the period of active C uptake will be critical if we are to manage rangelands for C sequestration.

The objective of this study was to compare forage production and foliar and basal cover responses of plant communities, plant functional groups, and individual species between years with below average (2004) and well above-average (2005) spring precipitation in three semi-arid rangeland ecosystems (shortgrass steppe, northern mixed-grass prairie, and sagebrush grassland). Foliar and basal cover at the time of a peak standing crop were visually estimated using modified Daubenmire cover categories, and forage production by species was harvested from areas that had been excluded from large herbivores. Responses of forage production to precipitation, but not foliar and basal cover, were similar for the three semi-arid ecosystems. Total forage production was more responsive (75–159%) than basal (8–35%) or foliar (2–29%) cover to increasing precipitation. Absolute (1016 kg·ha−1) and relative (159%) increases in total forage production from 2004 to 2005 were greatest for the shortgrass steppe. Forage production increases were largely attributable to greater production by C3 perennial graminoids in each ecosystem; increases in basal and foliar cover for this plant functional group were observed in shortgrass steppe and sagebrush grassland, but not in northern mixed-grass prairie. Fine-scale inputs of species and plant functional group responses to precipitation will further the accuracy of forage prediction models in predicting both total biomass production and relative proportions of plant biomass.

Restoration of ecological processes is key to restoring the capacity of ecosystems to support social, economic, cultural and aesthetic values. The sustainability of the restored system also depends on processes associated with carbon, nutrient and hydrologic cycles, yet most restoration monitoring is limited to plant community composition. Our research has shown that short-term plant composition monitoring is a necessary but insufficient predictor of long-term restoration success. Long-term (up to 75 years) studies in the western United States show that short-term monitoring of plant community composition alone incorrectly predicted the failure of treatments that were ultimately successful, and the success of treatments that ultimately failed. We propose that vegetation composition monitoring be combined with one or more ecological process indicators reflecting changes in three fundamental ecosystem attributes on which restoration success depends: soil and site stability, hydrologic function and biotic integrity. These simple, rapid, plot-level indicators reflect changes in resource redistribution and vegetation structure. We include a case study involving restoration of mixed grass prairie on mineland in the west-central United States.

Post-mining revegetation efforts often require grass seeding and mulch applications to stabilize the soils at the same time as shrub seeding, creating intraspecific competition between seeded shrubs and grasses that is not well understood. Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush) is the dominant premining shrub oil many Wyoming mines. The Wyoming Department of Environmental Quality, Land Quality Division requires reestablishment of I shrub m(-2) on 20% of post-mined lands in Wyoming. Reclamationists seldom document the impacts of grass competition on shrub canopy size after reclamation plantings become established even though shrub canopy development is important to vegetative structural diversity. In 1999, we initiated a study at the Belle Ayr Coal Mine near Gillette, Wyoming, to evaluate the influence of grass competition oil establishment and growth of Wyoming big sagebrush. Combinations of three sagebrush seeding rates (1, 2, and 4 kg pls ha(-1)) and seven cool-season perennial grass mixture seeding rates (0, 2, 4, 6, 8, 10, and 14 kg pls ha-1) were seeded during winter 1998-1999. Shrub density and grass cover were assessed from 1999 to 2004. We monitored sagebrush canopy size in 2001, 2002, and 2004. All sagebrush seeding rates provided shrub densities >= 1 shrub M after six growing seasons. Grass production >= 75 g m(-2) was achieved by seeding grasses at 6 to 8 kg pls ha(-1). Canopy growth of individual sagebrush plants was least in the heaviest grass seeding rate. Reduced grass seeding rates can aid in achieving Wyoming big sagebrush density standards and enhance shrub canopy growth.

ing the sustainable use of rangelands for livestock pro- duction. However, many ecosystem components and Growing interest in the potential for soils to provide a sink for processes like plant community structure, soil proper- atmospheric C has prompted studies of effects of management on the amountandnatureofsoilorganicC(SOC).Inthisstudy,weevaluated ties, and nutrient cycling are also affected by grazing effects of different grazing management regimes (light grazing (LG), management (Schuman et al., 1999). Density and dura- heavy grazing (HG), and non-grazed exclosures (EX)) on amount tion of rangeland stocking can affect plant community and composition of SOC at the USDA-ARS High Plains Grasslands compositionthroughdisplacementofcool-seasonmixed ResearchStation (HPGRS),Cheyenne, WY.Soils (0-5cm) fromeach grassesbywarm-seasonshortgrassesinnorthernmixed- treatment were analyzed for total C and N contents and lignin com- grass prairies (Dormaar and Willms, 1990). position. Soil organic C and N contents were significantly greater in Grazing can also influence the amount and composi- LG (SOC-13.8 Mg ha 1 ; total N-1.22 Mg ha 1

Effects of topsoil replacement depth on plant community development of reclaimed mined lands has been discussed for nearly three decades. Numerous research projects assessing topsoil depth effects were initiated during the 1970s. However, data collection for many of these studies was limited to 3-5 years. Plant community establishment, development, and stabilization through successional processes require considerable time. Only aboveground biomass and plant cover were reported in these short-term studies. In 2001, a research project initiated in 1977 was re-evaluated to assess the long-term effects of topsoil replacement depth (0, 20, 40 and 60 cm) on plant community development in south-central Wyoming. Percent grass cover and aboveground biomass were highest on the 40 and 60 cm topsoil depths, while forb cover was highest on the 0 and 20 cm depths. Percent bare ground was lowest on the 60 cm depth (30%) and highest on the 0 cm topsoil depth (62%). Plant species richness and diversity were significantly higher on the 0 cm topsoil depth and lowest on the 60 cm depth. Many native plant species established naturally in the abundant open space of the 0 cm topsoil replacement treatment. Variable topsoil replacement depth is a good management practice to enhance plant community diversity on reclaimed mined lands. However, placement of variable topsoil depths must consider erosion potential during the early years of reclamation. Areas of shallow topsoil should be limited to sites not prone to erosion, limited in size, and intermingled with other areas of greater topsoil replacement to ensure early stabilization and plant diversity of the reclaimed landscape.

We investigated the influence of long-term (56 years) grazing on organic and inorganic carbon (C) and nitrogen (N) contents of the plant–soil system (to 90 cm depth) in shortgrass steppe of northeastern Colorado. Grazing treatments included continuous season-long (May–October) grazing by yearling heifers at heavy (60–75% utilization) and light (20–35% utilization) stocking rates, and nongrazed exclosures. The heavy stocking rate resulted in a plant community that was dominated (75% of biomass production) by the C4 grass blue grama (Bouteloua gracilis), whereas excluding livestock grazing increased the production of C3 grasses and prickly pear cactus (Opuntia polycantha). Soil organic C (SOC) and organic N were not significantly different between the light grazing and nongrazed treatments, whereas the heavy grazing treatment was 7.5 Mg ha−1 higher in SOC than the nongrazed treatment. Lower ratios of net mineralized N to total organic N in both grazed compared to nongrazed treatments suggest that long-term grazing decreased the readily mineralizable fraction of soil organic matter. Heavy grazing affected soil inorganic C (SIC) more than the SOC. The heavy grazing treatment was 23.8 Mg ha−1 higher in total soil C (0–90 cm) than the nongrazed treatment, with 68% (16.3 Mg ha−1) attributable to higher SIC, and 32% (7.5 Mg ha−1) to higher SOC. These results emphasize the importance in semiarid and arid ecosystems of including inorganic C in assessments of the mass and distribution of plant–soil C and in evaluations of the impacts of grazing management on C sequestration.

Management practices can significantly influence carbon sequestration by rangeland ecosystems. Grazing, burning, and fertilization have been shown to increase soil carbon storage in rangeland soils of the Great Plains. Research was initiated in 2001 in northwestern South Dakota to evaluate the role of interseeding a legume, Medicago sativa ssp. falcata, in northern mixed-grass rangelands on carbon sequestration. Sampling was undertaken on a chronosequence of sites interseeded in 1998, 1987, and 1965 as well as immediately adjacent untreated native rangeland sites. Soil organic carbon exhibited an increase of 4% in the 1998, 8% in the 1987, and 17% in the 1965 interseeding dates compared to their respective native untreated rangeland sites. Nitrogen fixation by the legume led to significant increases in total soil nitrogen and increased forage production in the interseeded treatments. Increases in organic carbon mass in this rangeland ecosystem can be attributed to the increase in soil organic carbon storage and the increased aboveground biomass resulting from the increased nitrogen in the ecosystem. The practice of interseeding adaptable cultivars of alfalfa into native rangelands may help in the mitigation of elevated atmospheric carbon dioxide and enhance the long-term sustainability of the ecosystem.

Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) establishment on mined lands in Wyoming is a critical element of reclamation success. Because of its importance to wildlife, shrub density is used to assess reclamation success for wildlife habitat in Wyoming. Research was initiated at the Belle Ayr Mine near Gillette in 1999 to evaluate the effects of Wyoming big sagebrush seeding rates and grass competition on sagebrush establishment. Sagebrush seedling densities demonstrated consistent increases with increased sagebrush seeding rates. The 4 kg PLS per ha sagebrush seeding rate resulted in significantly greater density than either the 2 or 1 kg PLS per ha seeding rate in 1999 to 2001. Grass competition (grass seeding rates of 0, 2, 4, 6, 8, 10, and 14 kg PLS per ha of a mixture of C3 native species) did not significantly affect sagebrush seedling density. However, 1999 and 2000 precipitation was above or near normal, resulting in adequate moisture for seedling emergence and growth of all seeded species. Sagebrush seedling density declined at the higher grass seeding rates in 2001, but seedling density was not significantly affected by grass seeding rates (P = 0.12). Precipitation in 2001 was well below normal, and grass competition significantly affected sagebrush seedling canopy volume. Sagebrush seedling canopies were significantly smaller at grass seeding rates greater than or equal to 4 kg PLS per ha. Continued evaluation of these treatments on sagebrush seedling performance will enable development of a seeding strategy that enhances establishment of Wyoming big sagebrush on reclaimed mine lands. Introduction ____________________ Mined land reclamationists in the Western United States must meet many requirements to achieve successful reclamation. In August 1996, specific shrub density requirements were imposed on mine reclamation in Wyoming (Wyoming DEQ 1996). This standard required that the dominant postmining shrub on lands identified as wildlife habitat be reestablished at a density of 1 shrub per m on 20 percent of the disturbed landscape. Herbaceous species can create significant competition for shrub seedlings (Eissentat and Caldwell 1988; Schuman and others 1998; Williams and others 2002). However, reclamation guidelines and regulations require topsoil stabilization immediately after the topsoil is replaced using a permanent vegetation cover that is at least as productive as premine conditions. Establishment of a perennial vegetative cover that protects the topsoil resource from erosion can prevent the establishment of shrubs and other difficult-to-establish native plants. However, establishment of both herbaceous and shrub species is necessary to provide the desired plant community diversity and appropriate species for wildlife habitat. This study was conducted to further evaluate the establishment of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) when sown at three rates with a mixture of cool-season native grasses sown at seven seeding rates (competition levels). Methods _______________________ The study site was located at the RAG Coal West, Inc., Belle Ayr Mine, 29 km southeast of Gillette, WY. Climate at the site is continental, elevation is 1,460 m, mean air temperature is 6.7 ∞C and the average annual precipitation is 376 mm (Belle Ayr Coal Mine 2001). The premine vegetation of the area is a northern mixed-grass prairie primarily comprised of cooland warm-season grasses and Wyoming big sagebrush. Soils are derived from Tertiary and Upper Cretaceous shale, limestone, and sandstone. The topsoil was a sandy clay loam, with a pH of 7.6, EC of 2.0 dS per m, total nitrogen concentration of 700 mg per kg, and a soil organic carbon content of 1.0 percent. Topsoil replacement (56 cm) was completed in December 1997 to January 1998, and the area was seeded to barley (Hordeum valgare var. “Steptoe”) in April 1998 to establish a stubble mulch. In December 1998, seven grass seeding rate treatments (0, 2, 4, 6, 8, 10, and 14 kg PLS [pure live seed] per ha) were randomly drilled into 6.5 by 27 m main plots within each of four replicate blocks. The grass mixture (approximately equal seed numbers of each species) was

The potential to sequester carbon and increase organic nutrient storage in disturbed soils, such as those reclaimed after surface coal mining, appears to be significant. Quantification of organic carbon accumulation is complicated, however, by the presence of coal and coal dust in these soils. Our preliminary data on organic matter content of reclaimed soils at surface coal mines in Wyoming suggest they are sequestering carbon at a rapid rate. Data from a surface mine reclamation site near Hanna, WY indicate that surface (0-15 cm) soil organic carbon content has increased from a low of 10.9 g C kg-1 soil in 1983 to 18.6 g C kg-1 soil in 1998 and to 20.5 g C kg-1 soil in 2002. Undisturbed soil directly adjacent to the reclaimed site has a mean organic carbon content of 15.1 g kg-1 soil. At a mine near Glenrock, WY, soil organic carbon at a site reclaimed in 1979 increased from an estimated low of 5.8 g C kg-1 soil to a current level of 18.4 g C kg-1 soil. Organic carbon content of undisturbed soils adjacent to the reclaimed area range from 9.9 to 15.7 g C kg-1 soil. In contrast to the elevated organic carbon content, amounts of microbial biomass in reclaimed soils at both mines are lower than in nearby undisturbed soils (ca. 60% or less). We have collected similar data from a number of other surface coal mines in Wyoming. We hypothesize that decomposition rates are slow in reclaimed mine soils due to low microbial activity relative to that in undisturbed soils. Additional Keywords: carbon sequestration, reclaimed mine soil, soil organic matter, surface coal mine, soil microbial biomass

The enactment of state reclamation laws in the 1960's and enactment of Surface Mining Control and Reclamation Act (SMCRA) in 1977 brought the subject of mine land reclamation to the forefront. Early reclamation research was aimed at protection of the soil and water resources. Therefore, early emphasis was placed on proper topsoil salvage technology and re-establishment of a plant community that would protect the soil from erosion. With resource stability accomplished came the desire to establish a more diverse plant community and landscape that would allow the multiple use of the lands in this region, e.g. season-long forage production, recreation/aesthetics, watershed and wildlife habitat. Much research needs to be undertaken and technology developed before we will be able to create the diverse plant communities required to fully meet these multiple uses. Because of a general lack of understanding of many of the basic mechanisms by which plant communities develop, function and succeed, requirements for re-establishment of native warm-season grasses, forbs, and shrubs in the reclaimed community to reflect the diversity of the native or desired landscape remain unresolved. Past research has focused on community level issues in reclamation and has not assessed reclaimed lands at the ecosystem and landscape level, leading to considerable discussion and confusion as to a working definition of reclamation success and subsequent bond release. It is critical that all interested parties come together to develop the definition of reclamation success and understand the role of plant succession in achieving Afinal@ reclamation success. To achieve successful reclamation that meets the needs of potential land uses and takes into account natural succession will require a broader and more open-minded regulatory approach. Additional

Revegetation of mined rangelands in the western U.S. requires that a diverse, self-generating plant community be established that includes native woody shrubs that provide important wildlife habitat. Wyoming Department of Environmental Quality, Land Quality Division, on August 6, 1996, amended their revegetation standards to include a shrub densityrequirementthat had been sought by environmental and wildlife groups for over two decades. This standard requires that 1 shrub m· be re-established on 20% of the disturbed area and that 50% of this density be comprised of the dominant species present before mining. In Wyoming and much of the western rangelands, this typically requires the reestablishment of Wyoming big sagebrush (Artemisia tridentate ssp. wyomingensis). Hence, much research has been accomplished in the last 10-15 years to develop a better understanding of its seed physiology, seedbed ecology, and to develop cultural practices that will aid in its re-establishment. Research has increased our knowledge in many of these important areas of sagebrush reestablishment ecology and have greatly enhanced our ability to establish big sagebrush by direct seeding; however, climatic factors have a great influence on the success of its re-establishment. The paper also compares the cost of direct seeding compared to transplantation ofnursery grown seedlings to meetthe shrub density standard and shows that direct seeding costs only a fraction of the cost of transplantation. Further research efforts should be concentrated on further improving direct seeding technology and enhanced production of good quality seed. Additional