Increased Loss of DOC from Terrestrial Systems

Carbon released from terrestrial ecosystems is an important source of organic matter in most streams, lakes and rivers. In the Hudson River there has been a doubling in concentration of dissolved organic carbon over the past 15 years.

There have been multiple reports of increased dissolved organic carbon (DOC) yields from terrestrial systems resulting in higher DOC concentrations in diverse surface waters (See figure below; Findlay, S. E. G. 2005. Increased carbon transport in the Hudson River: unexpected consequence of nitrogen deposition? Frontiers in Ecology and the Environment 3:133-137.).

There are several plausible mechanisms potentially causing this increased carbon flux and we (with Gary Lovett) are investigating whether nitrogen deposition can cause greater DOC leaching from forest soils in the North East. Data from some N-fertilized plots shows greater DOC release while other sites show no effect. It seems likely that interactions with soil mineral layers or differences among sites in soil water flowpaths is contributing variability to results. Bioassays show that carbon released from some soils is metabolized by aquatic microbiota and supports rates of bacterial growth comparable to DOC from non-fertilized soils.

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