Abstract
Water table depth and vegetation are key controls of methane (CH4) emissions from peatlands. Microtopography integrates these factors into features called microforms. Microforms often differ in CH4 emissions, but microform-dependent patterns of belowground CH4 cycling remain less clearly resolved. To investigate the impact of microtopography on belowground CH4 cycling, we characterized depth profiles of the community composition and activity of CH4-cycling microbes using 16S rRNA amplicon sequencing, incubations, and measurements of porewater CH4 concentration and isotopic composition from hummocks and lawns at Sallie's Fen in NH, USA. Geochemical proxies of methanogenesis and methanotrophy indicated that microforms differ in dominant microbial CH4 cycling processes. Hummocks, where water table depth is lower, had higher porewater redox potential (Eh) and higher porewater δ13C-CH4 values in the upper 30 cm than lawns, where water table depth is closer to the peat surface. Porewater δ13C-CH4 and δD-CH3D values were highest at the surface of hummocks where the ratio of methanotrophs to methanogens was also greatest. These results suggest that belowground CH4 cycling in hummocks is more strongly regulated by methanotrophy, while in lawns methanogenesis is more dominant. We also investigated controls of porewater CH4 chemistry. The ratio of the relative abundance of methanotrophs to methanogens was the strongest predictor of porewater CH4 concentration and δ13C-CH4, while vegetation composition had minimal influence. As microbial community composition was strongly influenced by redox conditions but not vegetation, we conclude that water table depth is a stronger control of belowground CH4 cycling across microforms than vegetation.
Department
Soil Biogeochemistry and Microbial Ecology
Publication Date
8-6-2022
Journal Title
Journal of Geophysical Research: Biogeosciences
Publisher
Wiley
Digital Object Identifier (DOI)
Document Type
Article
Recommended Citation
Perryman, C. R., McCalley, C. K., Ernakovich, J. G., Lamit, L. J., Shorter, J. H., Lilleskov, E., & Varner, R. K. (2022). Microtopography matters: Belowground CH4 cycling regulated by differing microbial processes in peatland hummocks and lawns. Journal of Geophysical Research: Biogeosciences, 127, e2022JG006948. https://doi.org/10.1029/2022JG006948
Rights
© 2022. American Geophysical Union. All Rights Reserved.
Comments
This is a preprint of an author's manuscript published by Wiley in JGR: Biogeosciences in 2022, the Version of Record is available online: https://dx.doi.org/10.1029/2022JG006948