Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2012
Publication Date: 5/1/2012
Publication URL: naldc.nal.usda.gov.d2.nal.usda.gov/catalog/54350
Citation: Davies, K.W., Bates, J.D., Nafus, A. 2012. Vegetation response to mowing dense mountain big sagebrush stands. Rangeland Ecology and Management. 65(3):268-276. Interpretive Summary: Sagebrush reducing treatments may be needed in dense mountain big sagebrush stands to increase herbaceous vegetation. Prescribed fire is often used to treat dense sagebrush stands; however, mowing treatments are increasingly used because they are more controllable. However, information is limited on the effects mowing treatments on herbaceous vegetation. We evaluated vegetation responses to mowing treatments for three years post-treatment in mountain big sagebrush plant communities. Mowing treatments generally increased herbaceous cover, density, and production compared to the untreated areas. However, perennial forbs did not respond to mowing.
Technical Abstract: A decrease in fire frequency and past grazing practices has led to dense mountain big sagebrush (Artemisia tridentata spp. vaseyana (Rydb.) Beetle) stands with reduced herbaceous understories. To reverse this trend, sagebrush reducing treatments are often applied with the goal of increase herbaceous vegetation. Mechanical mowing is a sagebrush reducing treatment that is common applied; however, information detailing vegetation responses to mowing treatments are generally lacking. Specifically, information is needed to determine whether projected increases in perennial grasses and forbs realized and how exotic annual grasses respond to mowing treatments. To answer these questions, we evaluated vegetation responses to mowing treatments in mountain big sagebrush plant communities at eight sites. Mowing was implemented in the fall of 2007 and vegetation characteristics were measured for three years post-treatment. In the first growing season post-treatment, there were few vegetation differences between the mowed treatment and untreated control (P > 0.05), other than sagebrush cover was reduced from 28% to 3% with mowing (P < 0.001). By the second growing season post-treatment, perennial grass, annual forb, and total herbaceous vegetation was generally greater in the mowed than control treatment (P < 0.05). Total herbaceous vegetation production was increased 1.7- and 1.5-fold with mowing in the second and third growing seasons, respectively (P < 0.001). However, not all plant functional groups increased with mowing. Perennial forbs and exotic annual grasses did not respond to the mowing treatment (P > 0.05). These results suggest that the abundance of sagebrush may not be the factor limiting some herbaceous plant functional groups or they are slow to respond to sagebrush removing disturbances. However, this study does suggests that mowing can be used to increase herbaceous vegetation and decrease sagebrush in some mountain big sagebrush plant communities without promoting exotic annual grass invasion.