NET EROSION ON A SAGEBRUSH STEPPE LANDSCAPE AS DETERMINED BY CESIUM-137 DISTRIBUTION

Soil erosion plays a major role in structuring landscapes of semiarid regions. The purpose of this study was to examine patterns and assess transport mechanisms of soil erosion and deposition in a native sagebrush steppe landscape in south central Wyoming using Cs-137. Six landscape units were identified using a cluster analysis based on four landscape variables. Cesium-137 values varied little among landscape units, suggesting that intermediate-scale (approximately 100 m) fluvial and eolian soil transport is unimportant in this system during the time since bomb-test Cs-137 deposition occurred. In contrast, analysis of variance showed that, on windswept landscape positions, Cs-137 was significantly higher under shrubs than between them. These differences suggest that wind-driven redistribution has occurred at a small scale (0.5-10 m). Even though Cs-137 data indicate that intermediate-scale transport is not occurring, analysis of the soil fine fraction across the landscape shows net transport of fines downslope, suggesting that, in this sagebrush ecosystem, soil redistribution by fluvial erosion occurs too slowly to be determined by Cs-137.