B054-06
Shrub Encroachment Enhances Methanotrophy in a Minerotrophic Fen

Thursday, 10 December 2020: 10:50
Virtual
Clarice R Perryman, University of New Hampshire Main Campus, Durham, NH, United States, Carmody K McCalley, Rochester Institute of Technology, Rochester, NY, United States, Jessica Gilman Ernakovich, University of New Hampshire Main Campus, Natural Resources and the Environment, Durham, NH, United States, Louis J Lamit, Syracuse University, Syracuse, NY, United States, Joanne H Shorter, Aerodyne Research Inc., Billerica, MA, United States, Erik Lilleskov, USDA Forest Service, Northern Research Station, Houghton, MI, United States and Ruth K Varner, University of New Hampshire, Durham, NH, United States
Recorded Presentation
Abstract:
Rising temperatures may increase emissions of the radiatively important trace gas methane (CH4) from northern peatlands. Warmer and drier conditions have encouraged encroachment of shrubs and other woody vegetation in these same ecosystems. Recent work has characterized the impact of “shrubification” on peatland carbon cycling, but few studies have investigated the impact of shrub encroachment on methanogenesis and methanotrophy in peatlands. We sampled peat and porewater at 10, 30, and 60 cm depth at 8 plots divided between low ericaceous shrub cover (~30%) and high shrub cover (~60%) at Sallie’s Fen in NH, USA (43°12.50N, 71°3.50W). We investigated belowground CH4 dynamics using 16s rRNA sequencing and incubations of peat, as well as measurements of porewater CH4 concentration, CH4 isotopologues, and redox potential. The most abundant methanogenic genera across shrub cover classes and depth were Methanobacterium (0.34 ± 0.4%) and Methanoregula (0.31 ± 0.3%), and Methylocystis were the most abundant methanotrophs (2.3 ± 2.2%). While the relative abundance and community structure of methanogenic and methanotrophic lineages were more strongly affected by depth (ANOSIM, R = 0.44, p < 0.001) than shrub cover (ANOSIM, R = -0.07, p = 0.8), potential CH4 production and consumption varied across the shrub cover classes. Incubations indicate that CH4 production is higher in areas with low shrub cover (ANOVA, p < 0.001), and that CH4 oxidation is higher in areas with high shrub cover (ANOVA, p < 0.001). Similarly, dissolved CH4 concentration was lower (ANOVA, p = 0.06) and more enriched in 13C in the high shrub cover plots (ANOVA, p = 0.014), especially at 10 cm depth, which may indicate in situ oxidation as CH4 diffuses through the peat in areas with less plant-mediated transport through sedge aerenchyma. Our incubations and porewater measurements suggest that dominant Alphaproteobacterial methanotrophs at our study site may be more active in situ in the high shrub plots, which have more oxidizing conditions (ANOVA, p = 0.068) favorable to these methanotrophs. Additional isotopic measurements will further clarify the impact of shrub encroachment on belowground CH4 cycling at this site, but thus far our work suggests that shrubification promotes CH4 oxidation which may result in lower CH4 emissions.
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