ISOGENIE: Linking geochemistry, isotopic chemistry and microbial dynamics & community composition in a thawing permafrost peatland, Stordalen Mire, Abisco, Sweden
As permafrost thaws, increasing CH4 emissions from northern wetlands are likely to cause positive feedback to atmospheric warming. One of the over-arching goals of this project is to connect geochemical processes, particularly focusing on methane production, to underlying microbial population dynamics and genomics. Recent transformative technical advances in both high throughput investigations of microbial communities and high temporal resolution biogeochemical isotope measurements now permit a uniquely comprehensive approach to opening the microbial “black boxes” that impact carbon cycling on global scales. This project links detailed microbial sampling with detailed geochemical and isotopic sampling on seasonal and diel timescales and has an extensive modeling component. Gas exchange is monitored across the wetland gradients in a series of automated chambers and isotopes of emitted and belowground methane and carbon dioxide are measured with a QC laser system. The mire is in a state of partial thaw. With this thaw is an apparent ecological session in wetland community structure and associated changes in organic matter lability, rates of methane production and microbial community. Our group’s study sites range from palsa with underlying permanently frozen peat, to recently collapsed and flooded palsa, to flooded palsa colonized by Sphagnum, to flooded eriophorum sites, to sites populated by Carex, to open water lakes. Across this environmental gradient pH ranges from 4 to 6.5. This change is driven by changes in hydrology as the surface of the thawing permafrost subsides and an adjacent lake drains into the mire. Along this environmental gradient, from palsa to Carex, the lability of the peat increases significantly as determined in incubations of peat material and monitoring of methane and carbon dioxide production rates. Coincident with this environmental gradient is a decrease in the apparent fractionation factor between methane and carbon dioxide and methane isotopic composition becomes more 13C enriched, due to increased methane production via the acetate pathway.
Earth Sciences, Earth Systems Research Center
Fall Meeting, American Geophysical Union (AGU)
American Geophysical Union Publications
Chanton, J. etal. (2011), ISOGENIE: Linking geochemistry, isotopic chemistry and microbial dynamics & community composition in a thawing permafrost peatland, Stordalen Mire, Abisco, Sweden, Abstract GC41F-03 presented at 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec.