Location:2010 Annual Report
1a. Objectives (from AD-416)
Evaluate how management practices and disturbance processes interact to influence A) transitions/thresholds in ecological phases and states, B) plant community heterogeneity and nesting habitat for grassland birds, C) mechanisms and risk of weed invasion, and D) temporal dynamics of key ecological indicators of rangeland health. Subobjective A. Determine the influences of season and intensity of grazing, season and frequency of prescribed burning, and shifts in stocking rate on plant species composition, plant diversity, biomass production, animal gains and nesting habitat of a bird species of concern. Subobjective B. Evaluate the influences of fire X grazing interactions (i.e., patch burning) and prairie dog disturbances on within-pasture cattle grazing distribution, consequences for plant community heterogeneity and nesting habitat for a bird species of concern. Subobjective C. Determine how disturbance interacts with enemy release (the loss of specialized herbivores and diseases in the exotic range of a plant species) to influence weed invasion and the success of biological control. Subobjective D. Assess the temporal dynamics of key ecological indicators of rangeland health (plant cover and bare ground) for entire pastures in sagebrush and shortgrass steppe.
1b. Approach (from AD-416)
The planned research is designed to integrate contemporary goals of both livestock production and conservation in semiarid rangelands. Research will be conducted in shortgrass steppe, northern mixed-grass prairie and sagebrush steppe. Two experiments are replicated across three ARS locations (Miles City, MT; Nunn, CO; Woodward, OK) to determine ecological consequences of fire seasonality, return interval and grazing interactions along a north-south gradient in the western Great Plains. Rangeland monitoring efforts at two ARS locations with contrasting vegetation (grass-dominated shortgrass steppe, Nunn, CO; shrub-dominated sagebrush steppe, DuBois, ID) will use newly-developed techniques involving very large-scale aerial photography to assess plant cover and bare ground, and incorporate this information into a recently developed index to assess landscape function. Understanding the mechanisms that control disturbance effects on plant communities and animal responses will contribute to the development of innovative management strategies that optimize livestock production and conservation goals. In addition, because state-and-transition models function as a means for organizing current understanding of the processes resulting in stability and change in ecological systems, findings from these experiments will be incorporated into revised state-and-transition models of plant community dynamics that more accurately accommodate multiple successional pathways and stable states.
3. Progress Report
Progress was made on the main objective and four subobjectives, which address National Program 215 Objectives A.1, A.2, A.3, B.1, and C.1. Under Objective A.1 (Develop management and monitoring strategies and decision-support tools that conserve natural resources while maintaining economic objectives), we made substantial progress in developing management strategies that incorporate vegetation heterogeneity through interactions of grazing, prescribed fire and prairie dogs as a focal aspect of managing for both production and conservation goals on arid and semi-arid rangelands. Under Objective A.2. (Determine impact of livestock grazing, fire, mechanical treatments, and drought on ecological integrity and watershed structure and function), we made significant progress in understanding the interactions of livestock grazing and fire on vegetation structure for grassland bird habitat, grasshopper abundance, cactus mortality, livestock and pronghorn antelope behavior and use patterns and livestock production responses. Collectively, results from these experiments addressing NP 215 Objectives A.1 and A.2 have been incorporated into a USDA AFRI NIFA planning grant. Under Objective A.3. (Identify factors such as landscape position, species composition, land use history, management strategies, and climatic variables that can be used to predict and minimize the risk of degradation of rangeland ecosystems) we made progress to determine the influences of topography and water availability, through the topographic wetness index, and NDVI on livestock production across large spatial scales (>16,000 acres). Under Objective B.1. (Develop monitoring and decision-support tools and management strategies for land managers), we made substantial progress in the application and transfer of developed technology of very-large scale aerial imagery on arid and semi-arid rangelands in the western US. Progress was made in assessing critical wildlife habitat, determinations of revegetation success on dramatically disturbed lands such as pipelines, modifications in stream morphology following changes in grazing management on riparian areas, and efficacy of herbicide control efforts on large scales addressing invasive weeds. Under Objective C.1. (Understand mechanisms of weed invasion and develop management strategies that can be used to restore rangelands that have been degraded by weeds and other disturbances), we made substantial progress regarding the efficacy of restoring competitors and natural enemies for long-term control of weed invasion, the understanding of the synergy between availability of resources and natural enemies in weed invasion, and the contribution of carbon addition to reduce establishment of invasive weeds. Additionally, Unit scientists continue to be highly involved in literature assessments and monitoring efforts regarding the effectiveness of major conservation practices employed on private lands through the USDA-Natural Resources Conservation Service (NRCS) Rangeland Conservation Effects Assessment Program (CEAP).