Spatial and temporal patterns of tree water uptake between catchments of contrasting lithologies

Lithology may strongly control water uptake in vegetation. Soils weathered from different lithologies have different porosity and nutrient composition. As a result, trees may take up water from different soil depths in response to different vertical distribution of water and nutrients. Temporally, lithology may shift seasonal patterns of the rate and duration of water uptake by trees. Spatially, local heterogeneity of landscapes of different lithologies may create different water pools for individual trees. In this study, we used stable isotopes (²H and ¹⁸O) to compare tree water uptake processes between a shale catchment and a sandstone catchment. For each catchment, using natural isotope abundance in summer thunderstorms as a tracer, we cored sapwood of oaks and maples before and after four individual storms. Our sampling locations represented three different slope positions (e.g., ridge-top, mid-slope and toe slope) and curvatures (e.g., swale and planar hillslopes). From this study, we hope to test 1) whether different preferential flow pathways in soils shift tree preferences for event or pre-event water and 2) whether different landscapes driven by their underlying bedrocks scale tree water pools in different ways.