ASPECT RELATED MICROCLIMATE'S EFFECTS ON PEDOGENIC PROCESSES, HILLSLOPE EVOLUTION, AND VEGETATION DISTRIBUTION IN A SEMIARID WATERSHED, SEVILLETA NWR NEW MEXICO

The effects of aspect related microclimate on pedogenic processes and hillslope evolution were studied in a small, west draining watershed incised into pediment alluvium and limestone, sandstone, and mudstone of the Yeso and Abo Formations in the piedmont of the Los Pinos Mts. in central New Mexico. Apparent differences between cross canyon slopes exist where north facing slopes are steeper, have deeper, more developed soils, and more mesic vegetation than south facing slopes. This dissimilarity is explained by aspect related temperature and moisture gradients which drive differences in weathering, erosion, pedogenic processes, and vegetation distribution. Soil catenas and vegetation examined along the watershed representing differing degrees of incision suggest that temperature and moisture gradients between slopes become greater as aspect increases. Slope forms and characteristics appear to be controlled by weathering and erosion where pediment alluvium is transport limited, calcareous units are transport or detachment limited varying with moisture availability, and silicaceous units are detachment limited.