1a. Objectives (from AD-416):
The overall objectives are to develop accurate and efficient monitoring methods, management guidelines, and decision support tools for use on rangelands. These methods, guidelines, and tools will help rangeland managers maintain or improve the health of the nation’s rangelands. The following are our specific objectives. Objective 1: Evaluate newly developed monitoring technologies for landscape-scale assessment of the effects of rangeland management activities, including grazing and fire, on vegetation, ground cover, and herbivore selectivity. Subobjective 1.A: Quantify the accuracy, precision, and efficiency of very-large-scale-aerial (VLSA) and close-to-earth (CTE) imagery for measuring rangeland vegetation. Objective 2: Develop science-based grazing management strategies and decision support systems that can be used to guide managers to maintain or improve the ecological function of western rangelands. Subobjective 2.A: Assess the effect of shifts in plant species composition due to grazing and fire disturbance on ecological functions such as productivity, nutrient cycling, and hydrological function. Subobjective 2.B. Develop parameterization algorithms for the Rangeland Hydrology and Erosion Model (RHEM) from existing and newly collected rangeland hydrology data sets. Subobjective 2.C: Assess the indirect effects of sheep grazing activity, such as bedding and stream crossing, on infiltration, soil erosion, and water quality.
1b. Approach (from AD-416):
Subobjective 1.A. CTE imagery will be collected in 2 yr before and after grazing to determine whether this imagery can be used to accurately assess changes in vegetation due to grazing. The CTE method will be compared with more conventional methods. VLSA imagery will be collected at several scales from pastures that differ with respect to burning and postfire grazing rest to determine the efficiency and degree of specificity that vegetation classification can be accurately made with this methodology. Likewise the VLSA method will be compared with conventional methods. Subobjective 2.A. Prescribed fire in the spring, fall, or an unburned control will be the main plot treatments, and the burns will cause a shift in vegetation composition for the mountain big sagebrush community at the research location. Following the fire disturbances, different periods of postfire grazing rest will be imposed on subplots which may alter the rate of succession toward the preburned state for the burned main plots. Measurements of soil erosion due to wind and simulated rainfall, soil nutrient dynamics, and plant productivity, and animal productivity and behavior will be measured in each burn/postfire grazing rest treatment combination to determine what effect the resulting shifts in vegetation composition have on ecological function of this plant community. Subobjective 2.B. Data from Subobjective 2.A and other collaborators' data will be used to develop parameterization algorithms for RHEM. Multiple regression techniques will be used to develop algorithms that utilize plant and soil characteristics to estimate soil erodibility and hydraulic roughness. Subobjective 2.C. Sheep will be bedded on bedgrounds at our summer range. Measurements of infiltration, erosion, and runoff water quality will be measured from three treatments. The three treatments will be within the bedground and bedded in the measurement year, within the bedground but not bedded in the measurement year, outside the bedground in a similar site but only grazed in the measurement year.
3. Progress Report:
This research supports the 2007-2012 Pasture, Forage, Turf and Rangeland Systems National Program (NP 215) Action Plan, Component 1 (Rangeland Management Systems to Enhance the Environment and Economic Viability), Problem Statement A (Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems). Wildfires are part of rangeland ecosystems, and prescribed fires are part of programs to manage rangeland ecosystems, including shrub dynamics. ARS research scientists at the U.S. Sheep Experiment Station in Dubois, ID, and their collaborators used data from very-large-scale-aerial imagery to characterize the changes in horsebrush, bitterbrush, and sagebrush cover after wildfires and prescribed fires. A manuscript describing this research is currently being revised for resubmission to a peer-reviewed scientific journal. Wild and prescribed files remove vegetation that could have been used for livestock grazing, but grazing too soon after a fire may compromise ecological processes. ARS research scientists at the U.S. Sheep Experiment Station in Dubois, ID, conducted prescribed fires in autumn and spring to study the effects of season of fire (i.e., autumn vs. spring) and post-fire dormant-season grazing on plant community recovery rates and various ecological processes. Vegetation responses to fire and grazing treatments have been quantified using on-ground and very-large-scale-aerial imagery methods.
1. Spotted knapweed rapidly invades and destroys native rangelands. Cost-effective, novel, landscape-scale monitoring tools are needed to accurately and rapidly identify spotted knapweed plants in sagebrush ecosystems. Further, data for such tools should complement historic data collected with traditional methods. ARS research scientists at the U.S. Sheep Experiment Station in Dubois, Idaho, and their collaborators have established that aerial digital imagery is an effective tool for monitoring the frequency and density of spotted knapweed plants in various sagebrush steppe terrains. This research has resulted in monitoring tools that are better suited for landscape-scale monitoring of extensive rangelands.
2. Aerial imagery tracks shrub dynamics. Wildfires are natural part of rangeland ecosystems. Prescribed fires are used to manage rangeland ecosystems where natural fires were mitigated. Landscape-scale monitoring tools are needed to accurately measure and quantify postfire recovery of sagebrush ecosystems across intensive landscapes. ARS research scientists at the U.S. Sheep Experiment Station in Dubois, Idaho, and the ARS-Rangeland Resources Research Unit in Cheyenne, Wyoming, used data from very-large-scale-aerial imagery to characterize the changes in horsebrush, bitterbrush, and sagebrush cover after fires. This information will help land managers predict the optimal interval for prescribed burns and to plan landscape-scale prescribed fires to manage shrub cover.
3. Herbivore diet selection and vegetation composition. Knowledge of herbivore preferences for vegetation and vegetative composition of range could enable managers to predict the effects of grazing on standing vegetation. Close-to-earth imagery can be used to repeatedly capture visual standing vegetation before and during grazing events. ARS research scientists at the U.S. Sheep Experiment Station in Dubois, Idaho, completed experiments in tall-forb and sagebrush communities where close-to-earth imagery was used to monitor selectivity of grazing sheep. This will allow for the development of imagery-based monitoring tools that will enable managers to predict impact of grazing on standing vegetation based on the vegetative composition of a range or pasture.
Clark, P., Moffet, C.A., Lewis, G.S., Seyfried, M.S., Hardegree, S.P., Pierson Jr, F.B. 2012. Water quality effects of herded stream crossings by domestic sheep bands. Journal of Environmental Quality. 41:1-11.