Plant organic matter inputs exert a strong control on soil organic matter decomposition in a thawing permafrost peatland

Journal Article · Tue Jan 11 00:00:00 EST 2022 · Science of the Total Environment

DOI:https://doi.org/10.1016/j.scitotenv.2021.152757· OSTI ID:1925190

Wilson, Rachel M. ^[1]; Hough, Moira A. ^[2]; Verbeke, Brittany A. ^[1]; Hodgkins, Suzanne B. ^[3]; Chanton, Jeff P. ^[1]; Saleska, Scott D. ^[2]; Rich, Virginia I. ^[3]; Tfaily, Malak M. ^[2]; Tyson, Gene ^[4]; Sullivan, Matthew B. ^[3]; Brodie, Eoin ^[5]; Riley, William J. ^[5]; Woodcroft, Ben ^[4]; McCalley, Carmody ^[6]; Dominguez, Sky C.; Crill, Patrick M. ^[7]; Varner, Ruth K. ^[8]; Frolking, Steve ^[8]; Cooper, William T. ^[1]

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1. Florida State University, Tallahassee, FL (United States)
2. University of Arizona, Tucson, AZ (United States)
3. The Ohio State University, Columbus, OH (United States)
4. University of Queensland, Brisbane, QLD (Australia)
5. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
6. Rochester Institute of Technology, Rochester, NY (United States)
7. Stockholm University (Sweden)
8. University of New Hampshire, Durham, NH (United States)

Peatlands are climate critical carbon (C) reservoirs that could become a C source under continued warming. A strong relationship between plant tissue chemistry and the soil organic matter (SOM) that fuels C gas emissions is inferred, but rarely examined at the molecular level. Here we compared Fourier transform infrared (FT-IR) spectroscopy measurements of solid phase functionalities in plants and SOM to ultra-high-resolution mass spectrometric analyses of plant and SOM water extracts across a palsa-bog-fen thaw and moisture gradient in an Arctic peatland. From these analyses we calculated the C oxidation state (NOSC), a measure which can be used to assess organic matter quality. Palsa plant extracts had the highest NOSC, indicating high quality, whereas extracts of Sphagnum, which dominated the bog, had the lowest NOSC. The percentage of plant compounds that are less bioavailable and accumulate in the peat, increases from palsa (25%) to fen (41%) to bog (47%), reflecting the pattern of percent Sphagnum cover. The pattern of NOSC in the plant extracts was consistent with the high number of consumed compounds in the palsa and low number of consumed compounds in the bog. However, in the FT-IR analysis of the solid phase bog peat, carbohydrate content was high implying high quality SOM. Here, we explain this discrepancy as the result of low solubilization of bog SOM facilitated by the low pH in the bog which makes the solid phase carbohydrates less available to microbial decomposition. Plant-associated condensed aromatics, tannins, and lignin-like compounds declined in the unsaturated palsa peat indicating decomposition, but lignin-like compounds accumulated in the bog and fen peat where decomposition was presumably inhibited by the anaerobic conditions. A molecular-level comparison of the aboveground C sources and peat SOM demonstrates that climate-associated vegetation shifts in peatlands are important controls on the mechanisms underlying changing C gas emissions.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF)
• Grant/Contract Number: AC02-05CH11231; SC0010580; SC0016440; 2022070
• OSTI ID: 1925190
• Alternate ID(s): OSTI ID: 1842895
• Journal Information: Science of the Total Environment, Vol. 820; ISSN 0048-9697
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
peatland
climate change
greenhouse gas production
sphagnum
soil organic matter
decomposition