My current research focus is to understand the water source use patterns of riparian trees in the southeastern US and how changes in environmental variables impact source utilization. There have been many studies in arid locations, like those of the southeastern US and central Australia, showing that streamside trees, even when growing in the water, rely heavily on groundwater and often take up little or no surface water. It is theorized that this is because most surface water in these regions is not reliable enough to warrant root development in those zones as it is often snow-fed and dries up sometime during the summer. I am using stable isotopes of water to ask similar questions in the southeast, where surface water is reliable year round. If this ‘theory of unreliability’ holds true, it would be expected that species in these areas should be taking up a large portion of surface water. These studies examine species representative of riparian zones of the foothills of the southern Appalachians.
I have investigated these processes in plants growing along differing hydrologic regimes, between coexisting species, and among species growing along an elevational gradient.