Effects of canopy structure on water cycling: implications for changing forest compositionThis article is part of a larger document. View the larger document here.
In upland oak (Quercus spp.) forests of the Eastern United States, shade-intolerant, fire-tolerant oaks are being replaced by shade-tolerant, fire-sensitive species due to changes in forest management and fire regimes. In these mixed-species forests, rainwater redistribution by the forest canopy is determined by tree species traits as well as canopy position. To better understand how shifting forest composition could impact rainwater partitioning, we quantified differences in canopy structure and the resultant net flux of water to forest soils in a series of experiments across the Southeastern United States. Non-oak species had denser canopies than oaks and intercepted more rainwater, reducing throughfall by more than 15 percent. Conversely, stemflow water inputs were more than four times greater beneath non-oaks, which had smoother bark compared to rougher-bark oaks. This study demonstrates the link between aboveground tree structure and interspecific water fluxes. It supports the hypothesis that a shift in forest composition could influence future ecosystem function in southeastern upland oak forests.