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Project funded by NSF-OPP 0408371. PIs: G. Kling, K. Nadelhoffer, E. Rastetter, L. Johnson, M. Sommerkorn

 Developing Process-Level Understanding of Controls on Belowground Carbon and Nutrient Dynamics in Tundra Ecosystems

 Limited understanding of the production of roots and the fate of root-derived carbon additions to soils in the Arctic hinders accurate predictions of how global warming may affect the absorption or emission of greenhouse gases by plants. This project was designed to increase scientific understanding of these processes by examining the basic role of belowground roots and soils in carbon and nutrient cycling in tundra ecosystems. Researchers treated intact plots of tundra plots that were natural or fertilized with isotopic tracers to study the flow of carbon and nitrogen through root systems and into the soil. Findings indicate that even after 6 years the added radiocarbon label was still in sufficient abundance to trace the flow of carbon between different soil pools such as soil organic matter and microbial biomass, as well as in persistent plant tissues such as wood and evergreen leaves. However, after 3 years the added label in the gaseous and soil water samples was diluted to below detection in these rapid turnover pools. This was to be expected, and will be used to parameterize a mathematical model of the rates of C movement and transformation belowground.

 The major finding from this work has been that the contribution of roots alone to the dissolved pools of DOC, DIC, CO2 , and CH4 in the soils is much larger than previously thought. Results show that the total amount of dissolved carbon produced from the roots per m2 is ~300 times greater than the total output of dissolved carbon (per m2) from tundra catchments. This implies that a tremendous amount of carbon processing occurs somewhere on the landscape before draining from a watershed or flowing into the coastal oceans.

 Click here for NSF Final Report

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