Young, fast-growing forests can sequester huge amounts of carbon, but this potential is expected to be limited eventually by the nutrients required for biomass growth. Some forests are more productive than expected, given their age and available soil nutrients. In lowland Costa Rica, for example, experimental plantations were still highly productive and cycling large amounts of nitrogen after 22 years of growth. The broad aim of this research is to understand why these tropical forests remain productive. Specifically, this project will address the hypothesis that highly productive forests supply more carbon belowground to fine roots and soil microbes. Increased belowground allocation is expected to promote nutrient cycling largely through greater exploitation of soil resources by fine-root growth and microbial processes, which feed back to stimulate aboveground forest growth. A combination of large-scale and small-scale experimental approaches will be used to evaluate how carbon allocation to roots, symbiotic root microbes, and free-living soil microbes influence carbon and nitrogen cycling.

The results of this research will provide an improved understanding of the belowground pathways underlying tropical forest biogeochemistry, thereby advancing our ability to model and predict the role of forests in current and future global carbon and nitrogen cycling. This new information will inform planning and development of potential mitigation strategies in response to increasing atmospheric CO2. Furthermore, the project will facilitate student mentoring, field based student education, and international collaboration. To increase participation by underrepresented groups, an inquiry-based special short course in Tropical Field Biology will be offered; undergraduate students will be identified and recruited by the Directors of NSF Louis Stokes Alliances for Minority Participation Programs for Wisconsin and Illinois. The goal is to introduce these students to ecology and instill confidence and inspiration that will encourage them to apply for future research fellowships, and ultimately to graduate school.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Linda Deegan
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Duke University
United States
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