ARS | Publication request: Vulnerability of Permafrost Soil Carbon to Climate Warming: Evaluating Controls on Microbial Community Composition

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 22, 2010
Publication Date: August 22, 2010
Citation: Ernakovich, J., Challenger, A., Calderon, F.J., Wallenstein, M. 2010. Vulnerability of Permafrost Soil Carbon to Climate Warming: Evaluating Controls on Microbial Community Composition. Meeting Abstract. Poster presentation at the 13th International Society for Microbial Ecology Meeting. Aug. 22-27, 2010. Seattle, WA.

Technical Abstract: Abstract: Despite the fact that permafrost soils contain up to half of the carbon (C) in terrestrial pools, we have a poor understanding of the controls on decomposition in thawed permafrost. Global climate models assume that decomposition increases linearly with temperature, yet decomposition in thawed permafrost may be strongly controlled by the microbial communities that inhabit this extreme environment. In addition, the chemistry of this soil organic matter (SOM) that may be vulnerable to decomposition has not been well characterized. In many systems microbial community structure correlates to SOM quality and bioavailable-C, and I hypothesize that variation in the bioavailable-C and SOM quality in permafrost will affect microbial community structure. Active layer and permafrost soils were collected from Sagwon Hills, AK and permafrost samples were separated into 5cm depth increments. Diffuse reflectance Fourier-transformed mid-infrared spectroscopy (FT-IR) was performed to determine SOM quality, and 454 pyrosequencing is in progress. FT-IR results indicate that permafrost and active layer soils both contain organic functional groups that can be attributed to labile organic carbon, but permafrost soils have more features attributable to previously decomposed material, a trend which increases with depth. Carbon:nitrogen ratios also indicate that soil organic matter in the active layer has undergone less microbial degradation than in permafrost (42.1+6.5 versus 14.4+1.2). DNA fingerprinting indicates that permafrost communities are more diverse than the active layer; 454 pyrosequencing will provide more information about the differences in community composition. We expect that differences in the SOM chemistry between the active layer and permafrost layers will result in variation in the microbial species evenness and richness, suggesting that models predicting the carbon release from permafrost upon thaw should consider microbial community structure in addition to the currently used temperature response function.