Tree-DOM: Dissolved organic matter in throughfall and stemflow

Abstract

Rainfall onto trees entrains dissolved organic matter (tree-DOM). Tree-DOM is then exported down stems in stemflow and through leaves, branches, and gaps as throughfall. We synthesize tree-DOM literature, presenting trends in and controls of tree-DOM concentrations, fluxes, and chemistry. Tree-DOM concentrations are higher in stemflow (7–482 mg-C L−1) than throughfall (1–61 mg-C L−1) with both being enriched in DOM compared to rainwater. Per unit area of landscape, trees yield similar amounts of DOM as the streams draining those landscapes, indicating tree-DOM may provide a quantitatively significant carbon subsidy to stream and soil ecosystems. Tree-DOM chemistry is indicative of mixed sources likely dominated by organic molecules produced by the trees and supplemented by inputs from epiphytes and atmospheric deposition. Increased research is required to understand the sources of tree-DOM, the controls on tree-DOM concentrations and fluxes, and the significance of tree-DOM to aquatic C cycling.