9701765 Robertson While the loss of organic carbon and nitrogen via soluble forms has implications both for source and sink ecosystems, the extent and magnitude of fluxes are poorly known. Preliminary data from a range of ecosystems in an agricultural landscape in southwest Michigan suggest that fluxes of dissolved organic nitrogen can be quite significant. A review of the literature on leaching of soluble organic carbon and nitrogen, primarily studied in forests, suggests only abiotic controls. Several biotic controls are proposed here, given their large effect on the abiotic controls shown to significantly affect leaching of dissolved organic carbon and nitrogen(DOM). To better understand controls, an idea of the source of the leached DOM is critical. This study proposes a two tiered approach to looking at both aspects. A broad study of different ecosystems along a successional gradient and an intense study using isotopic tracers on the sources of leached DOM in one ecosystem. It is hypothesized that those factors which influence hydraulic flux will have the greatest effect on the mass loss of C and N through leached organic forms.
