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Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/5/2016 Publication Date: 4/25/2016 Publication URL: http://handle.nal.usda.gov/10113/62584 Citation: Davies, K.W., Bates, J.D., Boyd, C.S. 2016. Effects of intermediate-term grazing rest on sagebrush communities with depleted understories: evidence of a threshold. Rangeland Ecology and Management. 69:173-178. doi: 10.1016/j.rama.2016.01.002. Interpretive Summary: Millions of acres of sagebrush plant communities have been degraded by past improper management resulting in dense sagebrush stands with depleted herbaceous understories. Rest from grazing is often suggested as a treatment to promote recovery of these communities, but information on its effects are generally lacking. We evaluated the effect of intermediate term (5-6 years) rest from grazing on these plant communities. Perennial herbaceous cover was greater in ungrazed compared to grazed areas, but herbaceous vegetation densities, diversity, richness, litter and biological soil crust did not differ between treatments. These results suggest that intermediate term rest does not promote recovery of the herbaceous understory compared to moderate grazing in these communities. Technical Abstract: Millions of hectares of sagebrush (Artemisia L.) plant communities have been degraded by past improper management resulting in dense sagebrush stands with depleted herbaceous understories. Rest from grazing is often applied to promote herbaceous recovery from past mismanagement. However, the effect of intermediate term (5-10 years) rest from grazing in sagebrush communities with depleted herbaceous understories and dense sagebrush is relatively unknown. We compared well managed, moderate grazing (grazed) with intermediate term (5 and 6 years) rest (ungrazed) at five sites in southeastern Oregon. Sites were Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young) communities with dense sagebrush and depleted herbaceous understories. Perennial herbaceous cover was greater in ungrazed compared to grazed areas, but this was expected because herbivory removes foliar vegetation tissue (i.e. cover). Density of herbaceous vegetation, diversity, and species richness did not differ between ungrazed and grazed areas. Similarly, bare ground, litter, and biological soil crust cover did not differ between treatments. These results suggest that intermediate term rest does not promote recovery of the herbaceous understory compared to moderate grazing in these communities. The lack of effect from intermediate term rest on density, richness, and diversity, and that other restoration treatments have generally failed to restore the herbaceous understory in these plant communities illustrates the need to protect relatively intact herbaceous understories in Wyoming big sagebrush communities from degradation. The results of this study also suggest that Wyoming big sagebrush communities with a depleted herbaceous understory likely have crossed a threshold that may be difficult to reverse. |
