Are there benefits to mowing Wyoming big sagebrush plant communities? An evaluation in southeastern Oregon.

Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle & Young) communities frequently are mowed in an attempt to increase perennial herbaceous vegetation. However, there is limited information as to whether expected benefits of mowing are realized when applied to Wyoming big sagebrush communities with intact understory vegetation. We compared vegetation and soil nutrient concentrations in mowed and undisturbed reference plots in Wyoming big sagebrush plant communities at eight sites for three years post-treatment. Mowing generally did not increase perennial herbaceous vegetation cover, density, or biomass production (P > 0.05). Annual forbs and exotic annual grasses were generally greater in the mowed compared to the reference treatment (P < 0.05). By the third year post-treatment annual forb and annual grass biomass production was more than nine and sevenfold higher in the mowed than reference treatment, respectively. Our results imply that the application of mowing treatments in Wyoming big sagebrush plant communities does not increase perennial herbaceous vegetation, but may increase the risk that exotic annual grasses will dominate the herbaceous vegetation. We suggest that mowing Wyoming big sagebrush communities with intact understories does not produce the expected benefits. However, the applicability of our results to Wyoming big sagebrush communities with greater sagebrush cover and/or degraded understories needs to be evaluated.