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') 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 treatments, but not by the soil removal treatments. The 43% vegetation 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.Key Words: rainfall simulation, erosion, runoff, hydrology, sagebrush steppe Soil erosion is a major problem throughout the world (Meyers 1984, Pimentel et al. 1995 and has been recognized as a problem in the United States since the early 1900's (Sampson 1918). In the United States, an estimated 4.4 billion tonnes of soil are eroded by wind and water every year (Bills and Heimlich 1984). In many cases, these soil losses lead to increased sediment loads in streams and rivers which can reduce productivity of aquatic ecosystems, shorten the life span of ponds and reservoirs ResumenLa erosion del suelo ha sido vinculada a la sedimentacion de las corrientes de agua, la degradacion de ecosistemas y la perdida de productividad de pastizales. Sin embargo, se carece de conocimiento de como la perdida de suelo afecta la productividad de los pastizales o la sostenibilidad del ecosistema.Evaluamos el efecto de 3 niveles de reduccion de cobertura vegetal (0, 27 y 43%) y remocion de suelo (0,12 y 24 ton ha') en el escurrimiento superficial y la produccion de sedimento en una estepa de "Sagebrush" [Artemisia tridentata var. vasseyana (Rydb.) Beetle] bajo lluvia simulada. El tiempo de inicio del escurrimiento superficial fue afectado por los tratamientos de reduccion de cobertura vegetal, pero no por los de remocion de suelo. El tratamiento de 43% de reduccion de cobertura vegetal resulto en un menor tiempo de iniciacion del escurrimien...

Soil hydrological and erosional responses in patches and inter-patches in vegetation states in semi-arid Australia

“…Runoff was extracted using a vacuum pump and measured every minute during the first 5 min and then every 2 min until the end of the simulation. Runoff values were plotted over time to generate runoff hydrographs, and time to runoff (min) was defined as the time when the collected runoff exceeded 5% of the applied rainfall rate (Giordanengo et al, 2003). Average runoff rate (mm h −1 ) was computed for each rainfall simulation plot.…”