Ecohydrologic connectivity in semiarid watersheds of central Oregon

Abstract:

Understanding the hydrologic connectivity between upland-stream-groundwater components in conjunction with biological systems is crucial when managing semiarid ecosystems. This ongoing study conducted in semi-arid juniper woodlands in central Oregon aims to investigate how different ecologic and hydrologic components respond to the removal of overstory vegetation (i.e. juniper). The main objective is to characterize and compare ecohydrologic interactions occurring in treated (juniper removed) and untreated watersheds. Monitoring transects were established to determine vegetation-soil texture-soil water content relationships by aspect in both watersheds. Also, previously installed piezometers, soil moisture stations, and weather instrumentation were used to estimate precipitation-soil moisture-subsurface flow interactions in each watershed. Preliminary results suggest similarities in soil volumetric water content and vegetation composition when compared to aspect. Seasonal precipitation triggered an increase in soil water content at the deepest soil profile measured (80cm). This soil response and subsequent shallow groundwater level rise observed in selected piezometers seem to indicate a direct connectivity between precipitation, soil, and groundwater. These results were more evident in the treated watershed when compared to the untreated. Results from this study add to the understanding of hydrologic connectivity in semiarid watersheds.