Effects of a decade of grazing exclusion on three Wyoming big sagebrush community types

Authors: THOMAS, TYLER - Eastern Oregon Agricultural Research; Davies, Kirk; MATA-GONZALES, RICARDO - Oregon State University; Svejcar, Lauren; Clenet, Danielle

Submitted to: Global Ecology and Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2022
Publication Date: 11/17/2022
Citation: Thomas, T.W., Davies, K.W., Mata-Gonzales, R., Svejcar, L.N., Clenet, D.R. 2022. Effects of a decade of grazing exclusion on three Wyoming big sagebrush community types. Global Ecology and Conservation. 40. Article e02338. https://doi.org/10.1016/j.gecco.2022.e02338.
DOI: https://doi.org/10.1016/j.gecco.2022.e02338

Interpretive Summary: Exclusion of grazing has been suggested in drier sagebrush communities to prevent degradation and facilitate recovery. However, the effects of excluding moderate grazing by cattle remain largely unknown, especially across different sagebrush community types. We investigated excluding moderate grazing for over ten years in intact, degraded, and annual grass invaded sagebrush community types. We found that more than a decade of moderate grazing exclusion had negligible effects on plant community characteristics and did not accelerate recovery of degraded and invaded communities. These results suggest that grazing exclusion is not a preferred management practice compared to moderate grazing. These result are of interest to land and wildlife managers as well as other scientists.

Technical Abstract: Livestock grazing is the most extensive land use in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) steppe and its effects on plant community characteristics have been greatly debated. There have been calls to remove livestock grazing from public rangelands due to the negative impacts of historic overgrazing (heavy, repeated use during the growing season). However, most of the studies used to support grazing removal evaluated the impacts of excluding historic grazing, rather than the impacts of excluding moderate contemporary grazing (40-50% utilization, altering season of use) which has vastly different effects on plant communities. Thus, to understand the effects of removing contemporary grazing, we compared contemporary grazed areas to long-term (+10 yrs.) grazing exclusion areas in three common Wyoming big sagebrush community types: intact, degraded, and exotic annual grass-dominated types. Plant community characteristics (cover, density, diversity) were measured in 2020 and 2021 in five grazed and grazing excluded areas within each community type. The effect of grazing exclusion on Sandberg bluegrass (Poa secunda J. Presl) abundance and litter cover varied among community types, suggesting that grazing exclusion effects slightly varied among community types. However, most plant community characteristics were not influenced by grazing exclusion, suggesting that the removal of contemporary grazing has little effect on Wyoming big sagebrush plant communities. In contrast, most plant community characteristics varied among community types and between years, suggesting that grazing management plans need to account for the spatial and temporal variability among Wyoming big sagebrush communities. Furthermore, our results suggest that contemporary grazing exclusion has negligible effects compared to contemporary grazing on plant communities, and that exclusion of contemporary grazing (passive restoration) does not promote the recovery of degraded and annual grass invaded plant communities.