HR: 1340h
AN: B23D-1602    [Abstracts]
TI: Spatial Variation in Carbon Release From Arctic Tundra Resulting From Microtopography Created by Permafrost Thawing
AU: * Lee, H
EM: hannalee@ufl.edu
AF: Department of Botany, 214 Bartram Hall, University of Florida, Gainesville, FL 32611, United States
AU: Schuur, E A
EM: tschuur@ufl.edu
AF: Department of Botany, 214 Bartram Hall, University of Florida, Gainesville, FL 32611, United States
AU: Vogel, J G
EM: jvogel@ufl.edu
AF: Department of Botany, 214 Bartram Hall, University of Florida, Gainesville, FL 32611, United States
AB: One of the biggest potential feedbacks to global climate change from high latitude ecosystems may come from thawing of permafrost, which stores 30% of the total global terrestrial soil organic carbon (SOC). Thawing of permafrost may accelerate decomposition of soil organic matter (SOM) and increase carbon dioxide (CO₂) emissions and such emissions from soil can lead to further warming in global scale. When permafrost thaws in ice-rich areas, it creates localized topographical surface subsidence called thermokarst, which can induce variations in soil abiotic properties. By altering multiple resources in soil, thermokarst can change C cycling in high latitude ecosystems beyond simple increases in temperature alone. The objective was to determine how thermokarst affects ecosystem C exchange. We hypothesized that there would be a positive relationship between the degree of ground subsidence and CO₂ emissions from decomposition of SOM. This study was conducted in a tundra site near Denali National Park, Alaska. Three study sites were established according to the degree of surface depressions: Severe Thaw, Moderate Thaw, and Minimal Thaw. We established 50 equally spaced grid points each site and they were surveyed using GPS to measure the micro-elevation. Clear static chamber measurements were used to measure ecosystem C exchange, while soil properties such as temperature and volumetric water content (VWC) were measured simultaneously. Normalized Difference Vegetation Index (NDVI) was measured as an indicator of primary productivity. We used forward stepwise regression analysis to quantify how much microtopography explained ecosystem C exchange. There was a negative correlation between ecosystem respiration and relative elevation at the Severe and Minimal site. The best predictor variable for ecosystem C exchange was VWC alone, which was better than temperature alone, or mixed effects of temperature and VWC. There was no relationship between NDVI and microtopography, which supports the idea that thermokarst alters soil processes more than primary productivity. Subsided areas showed high CO₂ emissions; therefore, we suggest thermokarst development may play major role in stimulating CO₂ emissions from high latitude ecosystems.
DE: 0428 Carbon cycling (4806)
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
DE: 0708 Thermokarst
DE: 0718 Tundra (9315)
DE: 1600 GLOBAL CHANGE
SC: Biogeosciences [B]
MN: 2007 Fall Meeting