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 137Cs. 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 137Cs deposition occurred. In contrast, analysis of variance showed that, on windswept landscape positions, 137Cs 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 137Cs 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 137Cs.

Abstract. Soil nitrogen transformations and nitrous oxide fluxes were measured in a range of sagebrush steppe ecosystems in south-central Wyoming. Net nitrate production, measured in laboratory incubations, was highest in the ecosystem type dominated by Artemisia tridentata ssp. vaseyana, especially early in the growing season. Fluxes of nitrous oxide, measured in closed chambers and analyzed by gas chromatography, also tended to be higher in the same type, but only for short periods in the spring. Thereafter, all nitrous oxide fluxes were low and did not differ consistently among types. Estimated average annual fluxes for three Artemisia ecosystem types (dominated by Artemisia tridentata ssp. vaseyana, Artemisia tridentata ssp. wyomingensis, and Artemisia nova) were 0.32, 0.23 and 0.13 kg N,O-N ha-'y-r repsectively. Average annual flux, weighted by the areal extent of these and other vegetation types in the region, was approximately 0.21 kg N,O-N ha-'y-l. Assuming this landscape is representative of sagebrush steppe, we calculate a flux of 9.5 X lo9 g y-' of N,O-N from U.S. sagebrush steppe, and a flux of 1.1 X 10" g y-l of N,O-N from analogous desert and semi-desert shrublands of the world.

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