Transpiration patterns and water use strategies of beech and oak trees along a hillslope

The role of landscape topography in mediating subsurface water availability and ultimately tree transpiration is still poorly understood. To assess how hillslope position affects use, we coupled sap velocity with xylem isotope measurements a temperate beech-oak forest along transect Luxembourg. We generally observed greater velocities at the upslope locations trees from average-sized trees, suggesting presence more suited growing conditions. found lower difference among positions for larger likely due to exploitation deeper persistent sources canopy light interception. Beech exploited shallower seasonally less source than oak root system trees. different strategy could also explain stronger stomatal sensitivity beech vapour pressure deficit compared Xylem isotopic composition was variable all locations, mainly reflecting contribution soil that groundwater did not contribute, or only marginally contributed, transpiration. Overall, our results suggest rely on stored unsaturated zone shallow table may necessarily subsidize uptake species do tolerate anoxic Contrary previous studies, site, find higher downslope as structure promotes vertical flux over lateral redistribution vadose zone.