Effects of permafrost degradation on carbon balance of upland tundra

Susan M. Natali, University of Florida, natali@ufl.edu (Presenter)
Ted Schuur, University of Florida, tschuur@ufl.edu

Northern permafrost systems play a critical role in global carbon (C) cycling because of the vast pool of thermally-protected C stored in these ecosystems and the strong potential for changes in C storage in a warmer climate. Increased decomposition of previously frozen organic C may result in a significant positive feedback to global climate change; however, some respiratory C losses may be offset, in part, by warming-mediated increases in plant productivity. To determine the magnitude of warming effects on ecosystem C balance, we established a new warming experiment—the Carbon in Permafrost Experimental Heating Research (CiPEHR) project—where we increased air and soil temperatures and degraded surface permafrost. We used snow fences coupled with spring snow removal to increase deep-soil temperatures and thaw depth (winter warming) and open top chambers to increase summer air temperatures (summer warming). Here we present ecosystem C balance results from three years of experimental warming of upland tundra in Interior Alaska and describe our efforts to incorporate these results into ecosystem models. Winter warming significantly increased net annual CO2 loss from the ecosystem, which was driven by a two-fold increase in ecosystem respiration during the snow-covered period. While most changes to the abiotic environment at CiPEHR were caused by the winter warming treatment, summer warming effects on plant and soil processes resulted in 20% increases in both gross primary productivity and growing season ecosystem respiration and significantly altered the age and sources of CO2 respired from this ecosystem. These results demonstrate the vulnerability of organic C stored in near surface permafrost to increasing temperature and the strong potential for warming tundra to serve as a positive feedback to global climate change. Future research efforts will focus on combining field observations with laboratory incubation results and using data assimilation techniques to both modify the Terrestrial Ecosystem (TECO) model for use in permafrost ecosystems, and to parameterize this model in order to make projections of the response of tundra ecosystem C balance to future climate scenarios.

Presentation Type:  Poster

Session:  Global Change Impact & Vulnerability   (Tue 11:30 AM)

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Poster Location ID: 253