Understand the Mechanisms Underlying Heterotrophic CO2 and CH4 Fluxes in a Peatland with Deep Soil Warming and Atmospheric CO2 Enrichment
Scott Bridgham–University of Oregon
Jason Keller–Chapman University
Qianlai Zhuang–Purdue University
Anya Hopple, Postdoctoral Associate, Chapman University and University of Oregon
Laura McCullough and Cory LeeWays, MS. Students, University of Oregon
Funded by U.S. Department of Energy, Office of Biological and Environmental Research, Terrestrial Ecosystem Science Program
Peatlands are among the most important terrestrial ecosystems in the global carbon (C) cycle. These wetlands currently store roughly one-third of the terrestrial soil C and are a significant source of the potent greenhouse gas methane (CH4) to the atmosphere. A pressing challenge in global change biogeochemistry remains whether or not a significant fraction of the large soil C pool in peatlands will be mineralized to CO2 or CH4 in future climates. Given that CH4 has 28-times the global warming potential of CO2, understanding the response of peatland CH4 dynamics in response to global change is particularly critical for understanding peatland-climate feedbacks. Methane cycling in peatlands is complex. The production of CH4 is the result of multiple, anaerobic microbial processes in which different groups of microbes ‘cooperate’ by sequentially producing substrates for one another and compete for those substrates. Once produced, a significant fraction of CH4 can be oxidized to CO2 within peatlands by different microbial processes. Currently, Earth system models do not adequately capture the complexity of CH4 cycling in peatlands and are thus ill-equipped to predict the response of peatland CH4 emissions to global change – including elevated [CO2] and increased temperatures. The overall objective of this renewal is to expand our mechanistic understanding of how deep warming of peat and CO2 enrichment in a bog affect C mineralization and CH4 dynamics and to incorporate that understanding into Earth system models.
The Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) project will manipulate temperature (+0, +2.25, +4.5, +6.75 and +9 °C) and atmospheric CO2 concentrations (Ambient, +850 ppmv) in 9 m diameter plots within a northern Minnesota bog (S1 Bog). Warming through the entire ~2 m peat profile was initiated in June of 2014, and surface warming and CO2 enrichment will commence in spring 2015. This iOthers a large multidisciplinary project with the larger project led by Paul Hanson, Oak Ridge National Laboratory. Our role in this project is to examine anaerobic carbon cycling processes including fermentation reactions, methanogenesis pathways, homoacetogenesis, and anaerobic carbon cycling and to incorporate this new knowledge into the ecosystem models, with particular emphasis on the Terrestrial Ecosystem Model (TEM).