Ecohydrological processes are important drivers of vegetation establishment and growth. Subsurface properties have a significant impact on these processes controlling soil moisture and nutrient storage and rates of fluid transport. Geophysical techniques have been well established for locating geological features and resource deposits, but have not been widely tested as tools for determination of soil properties that control Ecohydrology. We hypothesized subsurface maps of soil properties could be used to better inform placement of experimental plots or environmental instrumentation. We used GPS-based electromagnetic induction (EMI) and electrical resistance imaging (ERI) to uncover subsurface details relating to soil properties (i.e., texture and depth) that control processes (e.g., flow and evapotranspiration).
Results/Conclusions
Existing instrumented plots within the T.W. Daniel Experimental Forest site in Northern Utah were examined using near-surface soil electrical conductivity maps revealing significant differences in soil texture across aspen, conifer, sage and grass treatments. In hindsight, tremendous benefit could be derived from EMI mapping of the study area to combine vegetation and soil electrical conductivity maps in the process of designating locations of vegetation plots for scientific study. The use of electrical resistance imaging, which probes deeper into the soil and resolves detailed vertical features, can be coupled with EMI maps to identify the soil textural profile and soil-bedrock interface. These provide detailed hydrologic information on the soil moisture reservoir capacity which is an important vegetation constraint in semi-arid climates. Geophysical techniques using electromagnetic and electrical methods, show great promise for ecohydrologic investigations where, for example a small watershed of 40 ha can be mapped using EMI in a single day. Further research is needed to more definitively link measured geophysical response to hydrologic and vegetative feedbacks.
