Land-use change impacts on carbon and nitrogen cycling and greenhouse gas emissions

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As human populations increase, rates of land-use change are accelerating, and terrestrial ecosystems are being threatened by anthropogenic stresses.  The proposed research explores how human disturbances alter key processes of carbon and nitrogen cycling in terrestrial ecosystems.  Key questions are 1) How do forest management practices alter forest structure and rates of carbon exchange with the atmosphere 2) How does afforestation of former agricultural land, and grasslands, influence soil carbon storage and 3) What is the fate of nitrogen added to forest ecosystems, and how do patterns of land use influence catchment-scale nitrogen retention? Using a combination of field studies, process-based models, and collaboration with remote sensing specialists, this research will address how forest management alters forest structure, and how variability in forest structure influences forest growth rate and net carbon storage over various spatial and temporal scales.  Different approaches and models will be tested at Howland Forest in Maine and at two Fluxnet Canada sites.  Using a chronosequence of afforested agricultural lands in Ontario, this research will quantify changes in carbon and nitrogen cycling processes following the conversion of former agricultural land to forests (afforestation or reforestation), and the impact on net carbon storage.  Based initially on results from Howland Forest in Maine, results from this research will explore the processes by which nitrogen added to a forest canopy moves through the ecosystem, and it's impact on net carbon storage.  Land-use and water quality data in Ontario, both historical and current, will be used to quantify catchment-scale factors that influence retention of exogenous nitrogen.   These results will be compared to those from other countries with vastly different sources of nitrogen and land-use patterns. This innovative research provides new insights into processes that control carbon and nitrogen cycling in terrestrial ecosystems.  This information will help inform innovative policy solutions to help solve key environmental issues facing society.