The Mechanistic Function of Terracettes in a Semiarid Rangeland Environment.

Understanding spatial variations in soil moisture is a critical part of runoff estimation and management of rangeland vegetation in semiarid ecosystems. Despite many decades of research quantifying the spatial variability in soil moisture patterns, limited knowledge exists on the complex interactions between microtopography and soil moisture variability, such as with contour trenching or terraces. The objectives of this study were to; (1) gain a mechanistic understanding of microtopographic terracette-feature influences on vadose zone hydrology, and (2) apply our process-based understanding of terracettes to rangeland management in Idaho. Satellite imagery was used to assess 1,000, 50-acre plots, partitioned equally between four classes of land ownership within Idaho. Our assessment estimated the presence of terracettes on more than 477,000 acres. Preliminary results show terracette presence at the plot and hillslope scale may lead to a decrease in soil moisture as compared to non-terracette sites. Differences between terracette and non-terracette plots were observed at depths of less than 30cm for a silt-loam under seasonal grazing use. To evaluate the application of terracette function to rangeland management we considered the effects of decreased antecedent moisture conditions on the output of the Rangeland Hydrology and Erosion Model and the implications this may have for best management practice selection on lands influenced by terracettes.