TREE-DOM: DOM FROM THE CROWNING HEADWATERS OF THE AQUATIC CARBON CYCLE

Studies of DOM transport through terrestrial aquatic systems usually start at the stream. However, the interception of rainwater by vegetation marks the beginning of the terrestrial hydrological cycle making trees the headwaters of aquatic carbon cycling. Rainwater interacts with trees picking up tree-DOM, which is then exported from the tree in stemflow and throughfall. Stemflow denotes water flowing down the tree trunk, while throughfall is the water that drips through the leaves of the canopy. Per unit area of landscape, trees yield similar amounts of DOM as the streams that drain those landscapes. The exported tree-DOM may find its way into streams and provides a carbon subsidy for soil microbes. Increased research is required to understand the significance of tree-DOM to soil and aquatic carbon cycling. We report tree-DOM export from two tree species (live oak and Virginian juniper) on Skidaway Island, Savannah, GA. DOC yields were high for both species and were elevated when the epiphyte, Spanish moss, was present. Stemflow DOM had higher color per unit carbon (SUVA) irrespective of tree species or epiphyte cover. However, cluster analysis of FT-ICR MS derived molecular signatures of tree-DOM revealed that each species has a unique molecular fingerprint irrespective of epiphyte cover and whether stemflow or throughfall was analyzed. These initial findings should prove useful as future studies seek to track tree-DOM across the aquatic gradient from canopy roof, through soils and into fluvial networks.