Abstract
The availability of labile carbon (C) compounds in Arctic wetland soils is expected to increase due to thawing permafrost and increased fermentation as a result of decomposition of organic matter with warming. How microbial communities respond to this change will affect the balance of CO2 and CH4 emitted during anaerobic organic matter decomposition, and ultimately the net radiative forcing of greenhouse gas emissions from these soils. While soil water content limits aerobic respiration, the factors controlling methanogenesis and anaerobic respiration are poorly defined in suboxic Arctic soils. We conducted incubation experiments on two tundra soils from field sites on the Seward Peninsula, Alaska, with contrasting pH and geochemistry to determine the pathways of anaerobic microbial respiration and changes with increasing substrate availability upon warming. In incubation of soils from the circumneutral Teller site, the ratio of CO2 to CH4 dropped from 10 to <2 after 60 days, indicating rapid depletion of alternative terminal electron acceptors (TEAs). Addition of acetate stimulated production of CO2 and CH4 in a nearly 1 : 1 ratio, consistent with methanogenesis, and the composition of the microbial community shifted to favor clades capable of utilizing the added acetate such as the Fe(iii)-reducing Geobacter and the methanogenic archaea Methanosarcina. In contrast, both CO2 and CH4 production declined with acetate addition during incubation of soils from the more acidic Council site, and fermentative microorganisms increased in abundance despite the high availability of fermentation products. These results demonstrate that the degree to which increasing substrate availability stimulates greenhouse gas production in tundra wetlands will vary widely depending on soil pH and geochemistry.
Original language | English |
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Pages (from-to) | 2070-2083 |
Number of pages | 14 |
Journal | Environmental Science: Processes and Impacts |
Volume | 22 |
Issue number | 10 |
DOIs | |
State | Published - Oct 2020 |
Funding
† This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, We thank Xiangping Yin for technical support and Xujun Liang for assistance in constructing the soil microcosms. This research was part of the Next Generation Ecosystem Experiments (NGEE-Arctic) project supported by the Office of Biological and Environmental Research, Office of Science, in the Department of Energy (DOE). All data supporting the conclusions of this work can be found on the NGEE-Arctic Data Portal (https://ngee-arctic.ornl.gov/data, DOI: 10.5440/1529131). Oak Ridge National Laboratory is managed by UT-Battelle LLC for DOE under contract DE-AC05-00OR22725.
Funders | Funder number |
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Office of Biological and Environmental Research | |
US Department of Energy | |
UT-Battelle LLC | DE-AC05-00OR22725 |
U.S. Department of Energy | |
Office of Science | |
Oak Ridge National Laboratory |