Temporal and Spatial Variation of Episodic Wind Erosion in Unburned and Burned Semiarid Shrubland

Whicker, Jeffrey; Breshears, David; Wasiolik, Piotr; Kirchner, Thomas; Tavani, Rebecca; Schoep, David; Rodgers, John

Redistribution or soil, nutrients, and contaminants is often driven by wind erosion In semiarid shrublands. Wind erosion depends on wind velocity (particularly during episodic, high-velocity winds) and on vegetation, which Is generally sparse and spatially heterogeneous In semiarid ecosystems. Further, the vegetation cover can be rapidly and greatly altered due to disturbances, particularly fire. Few studies, however, have evaluated key temporal and spatial components or wind erosion with respect to (i) erosion rates on the scale or weeks IS a function or episodic high-velocity winds, (ii) rates at unburned and burned sites, and (iii) within-site spatial heterogeneity in erosion. Measuring wind erosion In unburned and recently burned Chihuahuan desert shrubland, we round (i) weekly wind erosion was related more to dally peak wind velocities than to dally average velocities as consistent with our findings or a threshold wind velocity at approximately 7 m s-1; (ii) greater erodibility In burned vs. unburned shrubland indicated by erosion thresholds, aerodynamic roughness, and near-ground soil movement; and (iii) burned shrubland lost soil from intercanopy and especially canopy patches In contrast to. unburned shrubland, where soil accumulated in canopy patches. Our results are among the first to quantify post-fire wind erosion and highlight the importance or accounting for finer temporal and spatial variation in shrubland wind erosion. This finer-scale variation relates to semiarid land degradation, and is particularly relevant for predictions or contaminant resuspension and redistribution, both or which historically ignore finer-scale temporal and spatial variation In wind erosion.