Adaptive, multipaddock rotational grazing management: A ranch-scale assessment of effects on vegetation and livestock performance in semiarid rangeland

Authors: Augustine, David; Derner, Justin; FERNANDEZ-GIMENEZ, MARIA - Colorado State University; Porensky, Lauren; Wilmer, Hailey; BRISKE, DAVID - Texas A&M University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2020
Publication Date: 11/10/2020
Citation: Augustine, D.J., Derner, J.D., Fernandez-Gimenez, M., Porensky, L.M., Wilmer, H.N., Briske, D., the CRAM Stakeholder Group. 2020. Adaptive, multipaddock rotational grazing management: A ranch-scale assessment of effects on vegetation and livestock performance in semiarid rangeland. Rangeland Ecology and Management. 73(6):796-810. https://doi.org/10.1016/j.rama.2020.07.005.
DOI: https://doi.org/10.1016/j.rama.2020.07.005

Interpretive Summary: Over the past century, rangeland scientists and managers have studied and debated how grazing management strategies can be implemented to improve rangeland condition and increase livestock production in a sustainable manner on rangelands of western North America. One key question has been whether rotational grazing management, as opposed to season-long continuous grazing, can lead to desired changes in plant species that lead to enhanced forage and livestock production. However, many past studies on this subject have been criticized for (1) being done in small pastures that are not representative of real-world ranching operations, and (2) rotating cattle in way that do not use the principles of adaptive management. We conducted an experiment in shortgrass rangeland of eastern Colorado that was designed to overcome both of these limitation. We found that when rotational grazing is implemented in an adaptive manner (based on weather forecasts, real-time measures of forage condition,, and detailed monitoring of vegetation and cattle responses to management decisions), this management approach did not result in any desired improvements in vegetation condition or productivity, as compared to a traditional, continuous, season-long grazing management strategy implemented with the same stocking rate over a 5-year period. Furthermore, the rotational approach resulted in a significant reduction in livestock weight gains relative to the traditional approach in all 5 years of the experiment. Our research indicates that adaptive movements of livestock across a landscape can potentially have benefits for other desired outcomes, such as habitat for native wildlife, but is unlikely to generate desired outcomes for vegetation, at least over a 5-year time frame. We suggest that managers in semi-arid rangelands strive to maintain cattle at stock densities low enough to allow for maximal cattle growth rates, while still moving cattle over broad landscapes to achieve specific goals such as enhancing wildlife habitat or sustaining long-term sustainability of forage production.

Technical Abstract: A comprehensive understanding of multi-paddock, rotational grazing management on rangelands has been slow to develop, and the contribution of adaptive management and sufficient scale have been identified as key omissions. We designed an experiment to compare responses of vegetation and cattle in an adaptively managed multi-paddock, rotational system (hereafter, Collaborative Adaptive Rangeland Management; CARM) to that of a season-long, continuous system (Traditional Rangeland Management; TRM) at scales comparable to those of a working ranch. Each of 10 TRM pastures was grazed by a herd of yearling steers that occupied each pasture separately. CARM pastures were grazed by a single, 10-fold larger herd that rotated among pastures. Decisions regarding annual stocking rate and the sequence and timing of cattle rotations among pastures were made by an 11-member, CARM stakeholder group that included ranchers, land management agency professionals and conservation organization representatives. We hypothesized that year-long rest from grazing would increase the abundance and productivity of perennial C3 graminoids relative to continuous, season-long grazing. However, we found little supporting evidence for grazing management effects on C3 graminoid abundance or production under either above-average or below-average precipitation conditions during the first 5 years of treatments. Furthermore, CARM resulted in a 12 – 16% reduction in total cattle weight gain relative to TRM each year. Our work shows that the implementation of adaptive management by a stakeholder group provided with detailed vegetation and animal monitoring data was unable to fully mitigate the adverse consequences of high stock density on animal weight gain. We suggest that managers in semi-arid rangelands strive to maintain cattle at stock densities low enough to allow for maximal cattle growth rates, while still providing spatiotemporal variability in grazing distribution to enhance rangeland heterogeneity and long-term sustainability of forage production.