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Our proposed research represents an integrated program that will advance our understanding of the mechanisms responsible for altering Net Primary Productivity (NEP) under future levels of atmospheric CO2 and variable climate for a wide range of temporal scales (minutes to decade). The mechanisms considered as drivers for NEP changes are the result of forest physiology, structure, and species diversity. We developed an integrated set of tasks that address the component mechanisms responsible for quantifying NEP over a broad range of scales. Our proposed work will also focus on closure of NEP estimates from harvest components and net ecosystem exchange measurements under ambient conditions. The integration of all the mechanisms will provide a general understanding of how responsive NEP is for coniferous forests significantly contributing to the carbon "sink" in eastern North America. Our proposed studies of impending "downregulation" stem from preliminary observations in the FACE Prototype plot, as well as our current estimates of nitrogen cycling under ambient and elevated CO2 We can test this hypothesis, without disruption of site fertility, using the 15N-addition experiment in conjunction with on-going measurements and models that couple carbon and nitrogen dynamics. These studies provide additional relevance from the enhanced rates of nitrogen deposition that are currently experienced in eastern North America.
A major gap in our knowledge is concerned with the regulation of respiration in plants and soil carbon and its contribution to NEP. Our recent efforts to balance a soil carbon budget suggests that a mechanism not previously considered (e.g., exudation) may explain changes in soil carbon storage. |
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To address collectively all objectives, we assembled an interdisciplinary team of scientists with expertise in biogeochemistry, soil science, plant physiology, forest ecology and hydrology, atmospheric chemistry, and micrometeorology. Such investigation is one of the corner stones of the U.S. global carbon cycle initiative. Ultimately, this project provides unique scientific knowledge guiding the quantification at multiple time scales of biosphere-atmosphere exchange processes and climate feedbacks to the present and future global carbon cycle.
Further details can be found at The Duke University FACE Website
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