Project : USDA ARS

ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Rangeland Resources & Systems Research » Research » Research Project #436575

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

Location: Rangeland Resources & Systems Research

2024 Annual Report

Objectives
Objective 1-Determine the potential for adaptive grazing management to enhance beef production, vegetation heterogeneity, grassland bird conservation, carbon/energy/water balance, and soil health in western Great Plains rangelands. Subobjective 1.1–Compare responses of livestock, wildlife, plants, and soils to adaptive grazing management and traditional grazing management. Subobjective 1.2–Determine the contribution of flexible stocking strategies, adjusted annually based on forecasted weather and forage availability, to the sustainable intensification of livestock production. Subobjective 1.3–Determine the contribution of genetic variability (source population) in livestock, and its interaction with environmental variability and management strategies, to variability in livestock performance. Objective 2-Evaluate the impacts of droughts and deluges on shrub-grass interactions and carbon/energy/water fluxes and balances; learn how livestock management affects these responses. Subobjective 2.1–Quantify the effects of precipitation variability, extreme events (seasonal to multi-year droughts and individual deluges), topoedaphic variation, and livestock management on forage, livestock production, and carbon/energy/water fluxes. Subobjective 2.2–Evaluate the effects of increased interannual and intraannual precipitation variability and soil texture on grass-shrub competition, plant production, and forage quality. Objective 3-Identify temporal windows for spring grazing of cheatgrass to increase invasion resistance and forage production. Subobjective 3.1–Quantify temporal patterns of cattle consumption of cheatgrass and native, cool-season perennial grasses. Predict ideal grazing windows from associated measurements of climate, plant phenology, and forage quality. Subobjective 3.2–Test the utility of predicted grazing windows for controlling cheatgrass and increasing forage production. Objective 4-Evaluate where, when, and to what extent prairie dogs suppress livestock production in western Great Plains rangelands by altering forage resources and livestock foraging behavior. Subobjective 4.1–Quantify relationships between cattle weight gains and prairie dog abundance at pasture scales, at multiple sites, and across multiple years. Subobjective 4.2–Evaluate whether spatiotemporal patterns of livestock foraging can explain the mechanisms by which prairie dog abundance and distribution affect livestock weight gains. Objective 5-Provide land managers with information and decision tools needed to maintain profitability and environmental sustainability, and reduce risk to livestock operations in a changing climate. Subobjective 5.1–Simulate effects of adaptive grazing management on forage and livestock production in a spatially and temporally complex rangeland ecosystem; use simulations to explore alternative scenarios for stakeholder decision making. Subobjective 5.2-Evaluate the Wind Erosion Prediction System (WEPS) model at site and regional scales of rangeland agroecosystems. Subobjective 5.3-Develop interactive learning experiences and social networks to enhance stakeholder capacity for risk management and adaptation in a changing climate.

Approach
Semiarid rangelands of the western Great Plains simultaneously support livestock production and other ecosystem services such as wildlife habitat and soil carbon storage. To enhance decision-making by managers in these complex socio-ecological systems, we must first understand processes that regulate the provision of ecosystem services. The interactive effects of climate, soils, and management on forage production, plant invasion, livestock weight gain, and wildlife habitat are poorly understood. Moreover, key tools available to rangeland managers—adjusting stocking rates to match animal demand to forage availability, and moving livestock to better utilize spatially and temporally variable forage resources—are often underutilized. Through the coordinated and interdisciplinary work of eight scientists, we propose to: 1) conduct collaborative adaptive grazing management experiments, with direct involvement of diverse stakeholders, to balance multiple ecosystem services; 2) use intensive measurements of carbon fluxes and soil water to discover how precipitation interacts with topographic and edaphic variation to influence forage productivity and cattle weight gain; 3) use site-level models and cross-site comparisons to enhance predictions of key rangeland processes, including livestock weight gain and wind erosion; and 4) enhance stakeholder capacity for risk management and adaptation in a changing climate. To help achieve these goals we will leverage extensive historical data from the western Great Plains, participate in regional/national research efforts with other ARS units (e.g., Long Term Agroecosystem Research Network, USDA Climate Hubs, Grand Challenges, National Wind Erosion Network), and actively engage university partners, livestock producers, and other stakeholders.

Progress Report
The first objective focuses on the Collaborative Adaptive Rangeland Management (CARM) experiment, located in shortgrass steppe at the Central Plains Experimental Range (CPER). During this project cycle, we implemented years 6 – 10 of the experiment, which encompassed two severe droughts alternating with wet years. During the experiment, ARS scientists in collaboration with an 11-member stakeholder group made multiple adaptive changes to the CARM treatment, including annual adjustments in stocking rate, implementing a 2-herd rather than 1-herd rotation system, and implementing an improved drought management plan. The drought plan was made possible by a newly developed remote sensing tool that provides probabilities of forage biomass values at the pasture scale. Scientists successfully quantified how the CARM treatment affected cattle foraging behavior, diet quality, and weight gain in all 5 years, as well as effects on vegetation composition and productivity and grassland bird populations. New research efforts in 2023 and 2024 assessed enteric methane emissions of individual yearling cattle from herds originating in different climates and tested the use of virtual fencing to modify cattle distribution within pastures. The second objective is focused on how changes in precipitation influence the hydrology and productivity of semiarid rangelands. We incorporated eddy covariance data into an analysis by the Long-Term Agroecosystem Research (LTAR) network phenology working group. At CPER, we tested interactive effects of droughts and deluges on forage production and carbon cycling using both a precipitation manipulation experiment and a long-term (36-year) observational study of plant productivity data from a topographic sequence. In the Thunder Basin region of northeastern Wyoming (where sagebrush grassland, shortgrass steppe and northern mixed-grass prairie converge), we implemented a precipitation manipulation experiment to test effects of 1) greater interannual precipitation variability, and 2) more precipitation in the winter/early spring on plant productivity, drought stress and phenology. Results indicate that higher precipitation variability may negatively impact livestock forage in this system. Prior year addition of water followed by drought the next year led to high abundance of invasive annual bromes, but perennial grass production was resistant to increased precipitation variability. The combination of additional early spring water and increased interannual precipitation variability positively affected shrub cover and density after five years of treatment. We also implemented a second experiment that tested interactive effects of drought and grazing management strategies on plant communities, forage quality and quantity, and soil properties over five years in Thunder Basin and eastern Montana. This experiment found that two-year droughts increased the relative abundance of invasive annual plant species and had negative impacts on forage quality and quantity. Effects on forage quality were strengthened by heavy grazing during the drought and were long-lasting, persisting up to three years after drought ended. The third objective is focused on early spring grazing for control of cheatgrass in mixedgrass rangeland. During the project cycle, we implemented years 3 and 4 of the study, completing all fieldwork and laboratory work in 2021. This study enabled us to predict when cattle select for and against cheatgrass both within and among years. We used those predictions to create grazing windows - phenological periods when cattle are likely to be most effective in controlling cheatgrass. A second study was initiated using these predicted grazing windows to field test the degree to which early spring grazing can shift plant community composition towards desirable native species. In 2021, we selected a site that was heavily invaded by cheatgrass, constructed six replicated pastures, and collected pre-treatment plant community data. Beginning in 2022 we implemented early spring grazing treatments. Preliminary plant response data suggests that targeted grazing may effectively control cheatgrass in both wet and dry years. The fourth objective is focused on interactions between prairie dogs and cattle in the western Great Plains. During the project cycle, we monitored cattle foraging behavior via GPS collars at both CPER and the Thunder Basin site. We also collected data on prairie dog densities, vegetation composition, cattle diet quality, forage quality, and weight gains throughout the summer and fall. Furthermore, we used long-term monitoring data collected over the past two decades to evaluate how plague interacts with weather conditions to regulate the distribution and size of prairie dog colonies. Results were used to understand the impacts of prairie dogs and plague, as well as the drivers and consequences of cattle foraging behavior decisions in both shortgrass and mixedgrass rangelands. We have completed ten years of a long-term nested exclosure experiment testing the separate and combined effects of prairie dogs, livestock, and native grazing animals on forage quality, quantity, and composition in Thunder Basin. For each project, we provided data summaries to ranchers participating in these projects. The fifth objective addresses the provision of information and decision tools to land managers. The USDA Northern Plains Climate Hub continued to work with livestock producers and other rangeland managers to prepare for increasing weather variability and a changing climate. Grass-Cast, a grassland production forecasting tool that currently serves the Great Plains and the Southwest states of New Mexico and Arizona (https://grasscast.unl.edu) is a product of the USDA Northern Plains Climate Hub. Zoomable maps now allow users to decide for themselves whether the amount precipitation assumed by Grass-Cast is similar enough to precipitation received on their specific land area to trust resulting production estimates. Grass-Cast projections were used to determine the number of yearlings needed for a flexible stocking rate study that is designed to adaptively match animal demand with forage availability. Wind Erosion Prediction System (WEPS) Webstart was implemented by the Natural Resources Conservation Service (NRCS) in October 2023 for determining wind erosion estimates for conservation practices. A new web-based interface for the WEPS is nearing completion and will provide capacity to run both WEPS and the Water Erosion Prediction Project (WEPP) model together. During this project cycle, we adapted the Agricultural Policy/Environmental Extender (APEX) model (version 1605) for simulating rotational grazing management from 2014 to 2023. We facilitated model parameterization by incorporating PEST (parameter estimation) software and Monte-Carlo simulation, and improved accuracy by adding capabilities for simulating spatial and temporal heterogeneity. Simulation of grazing management scenarios showed that CARM decision criteria resulted in greater forage production compared to 7- or 14-day rotation intervals. The modified APEX model adequately simulated daily animal weight gain for both continuous, season-long grazing and adaptive multi-paddock rotational grazing.

Accomplishments
1. New remote sensing approach to reduce wildlife-livestock conflicts for ranchers and public land managers. Environmental conservation and economic sustainability can collide when wildlife and livestock compete for forage in working lands, creating challenges for private and public land managers. One example is competition between the black-tailed prairie dog, a keystone wildlife species, and livestock in the western Great Plains. ARS researchers from Fort Collins, Colorado, in collaboration with the Thunder Basin Grasslands Prairie Ecosystem Association and the USDA Forest Service used high spatial resolution remote sensing imagery and a deep learning approach to detect individual prairie dog burrows across vast areas of remote rangeland. Researchers were able to accurately map prairie dog colonies and vegetation use intensity, giving managers new remote sensing tools for understanding prairie dog population changes and their associated effects on livestock forage. In a related long-term experiment, the ARS researchers discovered that prairie dog impacts on cattle weight gain are often limited, but can increase substantially during drought years, when they can reduce revenue by 27% on some soil types. These efforts are currently helping managers understand where and when livestock production operations are at risk from prairie dogs, and informing management strategies for public and private lands. The findings indicate that successful mitigation of wildlife-livestock conflict depends on spatially explicit monitoring and management. If prairie dog conservation is focused on soil types where impacts to livestock production are low, producers may be able to reduce control costs and enhance coexistence of wildlife and livestock on Unite4d States rangelands.

2. Leaves not stems are critical for livestock production across the Great Plains. Forage production increases as precipitation increases in the Great Plains, but the response of livestock production along this gradient is unknown. ARS researchers in Fort Collins, Colorado, and Mandan, North Dakota, in collaboration with scientists from Colorado State University, Kansas State University, and South Dakota State University, analyzed long-term (20-30 years) livestock production data from six North American rangelands that varied from 13-33 inches of annual precipitation. They determined that, in contrast to the forage production response, livestock production declined in the sites with more precipitation, as plants had more stem than leaf material, which reduced forage quality and therefore lowered livestock performance. These results provide land managers with critical knowledge: Grazing management practices which increase leaf relative to stem growth in more mesic (wet) sites will increase livestock production and efficiency, as well as profitability.

U.S. DEPARTMENT OF AGRICULTURE

Rangeland Resources & Systems Research: Fort Collins, CO