Improving Pasture and Rangeland Management
The ARS pasture and rangeland management research program enhances the utility, function, and performance of rangelands, pastures, forage, and turf agroecosystems while providing ecosystem services. To support rural prosperity, food security, and healthy agroecosystems, ARS research helps producers improve management decisions and ultimately achieve healthy and productive pastures and rangelands, as illustrated by the following FY 2020 research accomplishments.
Powerful tools and techniques for monitoring rangeland production systems improve management and lower production costs. Standardized approaches for monitoring rangelands are needed to allow land managers and public land agencies to collect and share data that address numerous rangeland management and policy needs. ARS scientists in Las Cruces, NM, led the expansion of the rangeland monitoring program that directly supports the Bureau of Land Management (BLM) and Natural Resources Conservation Service (NRCS) national inventory and monitoring programs and the interagency National Wind Erosion Research Network. The Monitoring Manual for Grassland, Shrubland, and Savanna Ecosystems was published online, and physical copies were distributed to field staff. Statistical analysis tools and datasets were used by BLM and NRCS to produce reports and make management decisions regarding wildlife habitat suitability, evaluate conservation practice effectiveness, and improve grazing management systems across the continent’s rangelands.
Wind erosion network implementation to support a national assessment. Rangeland and cropland wind erosion reduces soil productivity and causes highway fatalities, human health problems, and infrastructure damage. Long-term networked research using standardized methodology is needed to accurately measure and model effects of management practices on wind erosion to mitigate this problem. ARS scientists in Las Cruces, New Mexico calibrated the Aeolian Erosion (AERO) model against sediment transport measurements collected in real time at National Wind Erosion Research Network sites. The model calibration included explicit representation of model uncertainty that can be communicated to stakeholders. Code was developed to apply AERO to large standardized vegetation monitoring datasets using the USDA SCINet Scientific Computing Initiative. The AERO model is now available for applications to assess wind erosion across western U.S. grazing lands.
Grass-Cast: A new decision-support tool helps livestock producers improve productivity from rangelands. Western U.S. livestock producers on rangelands can best manage their operations when they use flexible stocking strategies to match the forage needs of their animals with the forage availability on their land. Because forage growth varies greatly depending on precipitation, producers need ways to predict how much forage will be available to take advantage of flexible stocking strategies. ARS scientists from Cheyenne, Wyoming, and Fort Collins, CO, in collaboration with Colorado State University, the University of Arizona, and the National Drought Mitigation Center, developed Grass-Cast, a grassland productivity forecasting tool. Grass-Cast uses year-to-date climate data and seasonal precipitation outlooks to forecast forage production for rangelands at the 6 x 6-mile spatial resolution. Grass-Cast was publicly released in 2018 for the Northern Plains, in 2019 for the entire Great Plains, and in 2020 for New Mexico and Arizona. The public release included the co-development of a new website (https://grasscast.unl.edu), which was recently expanded in 2020 and is co-managed by the USDA Northern Plains Climate Hub and the National Drought Mitigation Center at the University of Nebraska. Grass-Cast has garnered widespread media coverage at regional and national levels, including a USDA official press release, blog posts, radio news stories, and stories in agricultural newspapers and websites. Livestock producers are interested in having Grass-Cast expanded to the Great Basin, California, and even Canadian prairies.
Post-wildfire rehabilitation strategies assessed. On average, $35 million per year is spent on post-fire rehabilitation treatments by the Bureau of Land Management (BLM) to reduce annual grass invasion and re-establish native communities that are resilient to future wildfire. Using a combination of field work and spatial analysis, ARS scientists in Reno, NV, examined the effects of fire, rehabilitation, and environmental variables on plant communities, cheatgrass invasion, and changes in fire regimes. Both elevation and aridity influenced cheatgrass invasion and future wildfire. Aerial seeding tended to increase future wildfires compared to drill seeding and planting of diverse bunchgrass communities after wildfire and rehabilitation were most successful in reducing cheatgrass invasion. These results suggest that post-fire rehabilitation treatments should focus on using a diverse assemblage of native grasses to reduce invasion by exotic annual grass species. These techniques are being used by BLM on more than 70,000 acres at the 2018 Martin Fire site with demonstrated success in establishing desired species and reducing cheatgrass density.
Determining plant properties and management practices that improve rangeland restoration after wildfire. Grasses are critical plants used in seeding rangeland in the western U.S. for restoration after wildfire and where invasive species threaten ecosystem function. These rangelands vary widely through the year in soil temperature and moisture conditions that affect grass seedling establishment, and grasses vary inherently in how well they establish. ARS researchers in Boise, ID; Burns, OR; Fort Collins, CO; and Woodward, OK; along with collaborators at the University of California, found that seeds planted later in the fall have a much higher chance of surviving winter mortality, and that diversifying the seed mix is key to ensuring that at least some seedlings successfully establish. ARS researchers in Logan, UT, examined the effect of soil water on root and shoot growth of seven grass species. Three species increased both root and shoot biomass in response to water, while four other grasses increased shoot growth but not root growth. They also found that higher seed mass produced seedlings with more shoot and root biomass that favors short-term growth, while less seed mass produced seedlings with greater surface area of leaves and roots that is better for long-term growth. These findings can improve successful seedling establishment by public land management agencies, help develop more recalcitrant native grass species, and match grass populations to specific site conditions—all to improve re-seeding efforts and make western rangelands more fire and weed resistant.