Plants and Wetland Methane Emissions
field work, Interior Alaska
Natural wetlands currently contribute 20–39% of global methane emissions and therefore influence climate change; however, at present, not only the amplitude but even the sign of the feedback between climate and wetland methane emissions is unknown. Much of this uncertainty is due to the unknown response of emissions to climate-induced changes in plant physiology and community composition. Wetland plants can both enhance and diminish methane emissions. We are working in thermokarst bog in Interior Alaska to quantify rates of methane production and oxidation, and to determine how changes in plant productivity alter these rates.
Plant growth experiments
We are augmenting field investigations with plant-growth experiments that use stable isotope labeling and a suite of novel genomic and molecular techniques to probe plant and microbial interactions in the soil zone surrounding roots (i.e., the rhizosphere) of Carex aquatilis, a water sedge at the site known to enable methane production and methane emission. The wetland rhizosphere is inhabited by complex microbial communities. With relation to the methane cycle, the important functional groups include methanogenic Archaea and methanotrophic Bacteria. The latter have to compete for oxygen with non-methanotrophic heterotrophic microbes, and all compete for carbon released by roots. Our goal is to ascertain how activities of these different microbial populations respond to root inputs of oxygen and carbon.
Results from both efforts will:
Advance understanding of how current and expected changes in plant productivity will alter methane production and methane oxidation in wetlands, which will contribute to improved representations of this response in large-scale methane models and will lead to more robust predictions of future methane emissions and climate–methane feedbacks.
Neumann, R. B., S. J. Blazewicz, C. H. Conaway, M. R. Turetsky, and M. P. Waldrop (2016), Modeling CH4 and CO2 cycling using porewater stable isotopes in a thermokarst bog in Interior Alaska: results from three conceptual reaction networks, Biogeochemistry, 127(1), 57–87, doi:10.1007/s10533-015-0168-2.
Neumann, Rebecca B; Blazewicz, Steven J.; Conaway, C. H.; Turetsky, Merritt R; Waldrop, Mark P. 2015. Modeling CH4 and CO2 cycling using porewater stable isotopes in a thermokarst bog in Interior Alaska: Results from three conceptual reaction networks, Bonanza Creek LTER - University of Alaska Fairbanks. BNZ:610, http://www.lter.uaf.edu/data/data-detail/id/610. doi:10.6073/pasta/c246d9ed17292fe6b0654cdd88a56deb