Patterns of Dissolved Organic Carbon and Nitrogen Cycling in a Southern Appalachian Hardwood Forest.

Net ecosystem production (NEP) is a measure of carbon accumulation by ecosystems and is calculated as the balance of gross primary production (GPP) and respiration.  Estimates of NEP are made at an ecosystem level using Eddy Flux covariance methods or by traditional plot based measurements of photosynthesis and net soil and plant respiration.  However, carbon loss beyond respiration, such as leaching of dissolved organic carbon (DOC) is often ignored. We measured monthly DOC and DON fluxes through a forest ecosystem including precipitation, throughfall, shallow (15 cm) and deep (90 cm) soil solution.  Seasonal patterns of DOC and DON show greater throughfall fluxes during the growing season.  Examining annual averages we measured a 10 fold increase in DOC concentrations as precipitation moves through the canopy, followed by decreasing concentrations as water moves through the soil profile from shallow to deep lysimeters.  DOC concentrations in deep lysimeters were greater than stream DOC concentrations, while DON concentrations were similar.  Calculation of DOC and DON fluxes will allow estimation of the importance of these components in ecosystem C and N cycling.