Project : USDA ARS

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Research Project: Adaptive Grazing Management and Decision Support to Enhance Ecosystem Services in the Western Great Plains

Location: Rangeland Resources & Systems Research

2020 Annual Report

Accomplishments
1. Effects of multiple, interactive disturbances in the Thunder Basin Ecoregion. To support sound land management decisions, rangeland managers require knowledge of how disturbances influence vegetation and ecosystem function. Such knowledge was previously lacking for northeastern Wyoming, which is a complex, diverse ecosystem located in a transitional zone (ecotone) between the Great Basin and the Great Plains. Using a stakeholder-driven research approach in collaboration with the Thunder Basin Grasslands Prairie Ecosystem Association, the University of Wyoming, and the USDA Forest Service, ARS scientists from Fort Collins, Colorado, and Cheyenne, Wyoming, demonstrated that: 1) wildfires do not promote cheatgrass invasion in this system, but they do lead to long-term ecosystem change by removing shrubs and shifting herbaceous species composition; 2) prairie dogs and historical wildfires shape vegetation structure more than short-term livestock management; 3) prairie dogs are associated with shorter structure vegetation and higher quality herbaceous forage throughout the growing season; 4) prairie dogs suppress forage biomass in droughts but not in average to wet years; and 5) prairie dog colonies and wildfire disturbances support high grassland bird diversity and sensitive bird species. Results demonstrate that transitional zones such as Thunder Basin can function differently from adjacent, well-studied regions such as the Great Plains or the Great Basin. These discoveries played key roles in the development of candidate conservation agreements (CCAs) between private landowners and the U.S. Fish and Wildlife Service, and a new USDA Forest Service management plan which aims to better balance needs of livestock production and biodiversity conservation on the Thunder Basin National Grassland. Moreover, ARS scientists are using these results to update Ecological Site Descriptions and associated state-and-transition models for the region via a formal USDA-NRCS process.

2. Stocking rate decision-support to enhance resiliency of rangeland livestock operations. Flexible stocking strategies match animal demand with variable forage availability for rangeland livestock operations. However, uncertainty in precipitation often prevents use of flexible stocking strategies across the western U.S. ARS scientists from Cheyenne, Wyoming, and Fort Collins, Colorado, in collaboration with scientists from Colorado State University, integrated eight decades of livestock production and climatic data to produce an enhanced stocking rate decision tree for western Great Plains rangelands. The decision tree incorporated influences of hierarchical temporal precipitation controls for livestock production, as temperature was not influential. Results showed that indices of decadal-scale sea surface temperatures off the Pacific Coast (Pacific Decadal Oscillation [PDO] phases) and a shorter-term (1-4 year) sea surface temperature fluctuations at the equator (El Nino Southern Oscillation phase) can be combined with local-scale (1-3 month) precipitation patterns to improve predictions of livestock weight gains in the western Great Plains. This decision tree substantially reduces enterprise risk enabling managers to make timely stocking rate adjustments without knowledge of impending growing-season precipitation amount. This innovative tool empowers livestock managers to make proactive stocking rate decisions, thus increasing profitability, production efficiency, and environmental sustainability on western U.S. rangelands.

3. Soil surface characteristics influence fine dust emissions on US drylands. Wind erosion and blowing dust in U.S. dryland ecosystems threaten food security through loss of productive soils and human health through reduced air quality and visual constraints for safe driving conditions. ARS scientists in Fort Collins, Colorado, in collaboration with scientists from the U.S. Geological Survey, Kansas State University, and Shandong Agricultural University and Beijing Normal University, China, conducted a series of wind tunnel and field experiments to understand and predict the effects of surface characteristics on fine dust emissions. The wind tunnel studies provided a 3-D computer simulation of wind flow through a plant canopy, demonstrated that fine dust emissions from abrasion of soil clods were greater for sandy soils than finer textured soils, and provided predictive equations for very fine dust emissions. A complementary field study demonstrated that bare soil inoculated with locally collected biological soil crust produced sediment-accumulating benefits within four-months, especially when combined with a soil stabilizer, indicating potential for dust mitigation in drylands. These results further quantify fine dust emissions from a variety of land surfaces, improve predictive wind erosion models of dust emissions, and provide promising methods for reducing dust emission from drylands, which together improve our ability to predict dust sources and develop controls for improved air, soil and water quality in the western U.S.

U.S. DEPARTMENT OF AGRICULTURE

Rangeland Resources & Systems Research: Fort Collins, CO