Constraints on microbial communities, decomposition and methane production in deep peat deposits

Journal Article · 06 February 2020 · PLoS ONE

DOI: https://doi.org/10.1371/journal.pone.0223744 · OSTI ID:1598371

Kluber, Laurel A.  ^[1]; Johnston, Eric R.  ^[2]; Allen, Samantha A.  ^[3]; Hendershot, John Nicholas ^[4]; Hanson, Paul J.  ^[2]; Schadt, Christopher Warren  ^[5]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Novozymes Inc., Salem, VA (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tennessee Technological Univ., Cookeville, TN (United States)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Stanford Univ., CA (United States)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

Peatlands play outsized roles in the global carbon cycle. Despite occupying a rather small fraction of the terrestrial biosphere (~3%), these ecosystems account for roughly one third of the global soil carbon pool. This carbon is largely comprised of undecomposed deposits of plant material (peat) that may be meters thick. The fate of this deep carbon stockpile with ongoing and future climate change is thus of great interest and has large potential to induce positive feedback to climate warming. Recent in situ warming of an ombrotrophic peatland indicated that the deep peat microbial communities and decomposition rates were resistant to elevated temperatures. In this experiment, we sought to understand how nutrient and pH limitations may interact with temperature to limit microbial activity and community composition. Anaerobic microcosms of peat collected from 1.5 to 2 meters in depth were incubated at 6°C and 15°C with elevated pH, nitrogen (NH₄Cl), and/or phosphorus (KH₂PO₄) in a full factorial design. The production of CO₂ and CH₄ was significantly greater in microcosms incubated at 15°C, although the structure of the microbial community did not differ between the two temperatures. Increasing the pH from ~3.5 to ~5.5 altered microbial community structure, however increases in CH₄ production were non-significant. Contrary to expectations, N and P additions did not increase CO₂ and CH₄ production, indicating that nutrient availability was not a primary constraint in microbial decomposition of deep peat. Our findings indicate that temperature is a key factor limiting the decomposition of deep peat, however other factors such as the availability of O₂ or alternative electron donors and high concentrations of phenolic compounds, may also exert constraints. Continued experimental peat warming studies will be necessary to assess if the deep peat carbon bank is susceptible to increased temperatures over the longer time scales.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC05-00OR22725; 3ERKP788
• OSTI ID: 1598371
• Alternate ID(s): OSTI ID: 1607318
• Journal Information: PLoS ONE, Vol. 15, Issue 2; ISSN 1932-6203
• Publisher: Public Library of ScienceCopyright Statement
• Country of Publication: United States
• Language: English