Hydrologic and sediment responses to vegetation and soil disturbances

Abstract

Soil erosion has been linked to stream sedimentation, ecosystem degradation, and loss of rangeland productivity. However, knowledge of soil loss, as it affects rangeland productivity or ecosystem sustainability is lacking. We evaluated the effects of 3 levels of vegetation cover reduction (0, 27%, and 43%) and soil removal (0, 12, and 24 tonnes ha-1) on soil surface runoff and sediment yield in a sagebrush [Artemisia tridentata var. vasseyana (Rydb.) Beetle] steppe under simulated rainfall. Time to runoff initiation was affected by the vegetation cover reduction treat- ments, but not by the soil removal treatments. The 43% vegeta- tion canopy reduction treatment resulted in a shorter time to runoff initiation than did the 27% and 0% canopy reduction treatments (p = 0.002). Results from analysis of covariance indicated that vegetation reduction and soil removal did not significantly affect sediment yield or runoff quantities in the first year following treatments. Multiple regression analysis revealed total sediment yield was related to forb cover, sand in the upper soil profile (0-5 cm), and the amount of bare ground. Time to runoff initiation was positively correlated with slope. Despite the lack of significant treatment differences, we do not conclude that these soil removal and vegetation reduction treatments had no affect on soil surface hydrology and sediment yield. There are numerous studies that show a strong relationship between vegetation reduction and soil erosion. Future research at this site may reveal long-term treatment effects that were not apparent in first year results.