Exploration of Possible Feedback Mechanisms for Carbon and Nitrogen Cycling in a Forested Ecosystem in Response to Global Climate Change

Alterations in carbon and nitrogen cycling in northern forests due to climate change could substantially affect the forests' ability to fix carbon, with consequent feedbacks for global warming. This study was conducted to evaluate the distribution of additional mineralized nitrogen within the heated plots at the Soil Warming experiment at Harvard Forest in Petersham, MA. Elevated soil temperatures at the Soil Warming site have been maintained since 1991 using heating wires inserted beneath the soil surface. Carbon and nitrogen content of vegetation and soil samples were found to be altered by warming, although these results were statistically significant (p<0.05) in only a few cases. There was no significant difference in plant productivity between heated and non-heated plots. Although heating appears to be shifting concentrations of nitrogen and carbon within the ecosystem, there is no evidence that soil warming contributes to increased nitrogen uptake by plants. Predictions pertaining to the impact of the northern forest on the future of global climate change and assuming an enlargement of the carbon sink due to soil warming may therefore yield misleading results.