Influence of Permafrost Thaw, Microtopography, and Precipitation on Methane Cycling in Northern Peatlands

• Main Author: Perryman, Clarice Rachelle
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2022
• Subjects: carbon cycle; methane; microbial ecology; peatlands; stable isotopes; wetlands; Stordalen; permafrost
• Online Access: https://scholars.unh.edu/dissertation/2725; https://scholars.unh.edu/context/dissertation/article/3724/type/native/viewcontent/Perryman_unh_0141D_11456_DATA.xml_AWSAccessKeyId_AKIAYVUS7KB2I6J5NAUO_Signature_toEWyaLkc3hILGtYEphHOjWtI_2BA_3D_Expires_1684690754

Northern peatlands are both globally important carbon (C) stores and sources of methane (CH4). The impacts of climate change including warming, changing precipitation and hydrology, shifts in vegetation, and thawing permafrost may increase the vulnerability of the northern peatland C stock, including the amount of C lost to the atmosphere as CH4. Variation in peatland water table depth strongly influences CH4 cycling, as water table levels largely control redox conditions and therefore rates of anaerobic CH4 production (methanogenesis) and aerobic CH4 oxidation (consumption, methanotrophy). As CH4 emissions reflect the balance of methanogenesis and methanotrophy, changes in water table depth due to landcover change, microtopography, or changes in precipitation strongly influence CH4 emissions across northern peatlands. Vegetation also impacts peatland CH4 cycling by affecting the quality and quantity of labile C inputs and the exchange of CH4 and oxygen between the atmosphere and the subsurface. As northern peatlands have high spatial heterogeneity in water table levels and vegetation, CH4 emissions often vary strongly across the landscape.The first portion of this dissertation examines how site-scale landscape heterogeneity impacts belowground CH4 cycling. This work was conducted in a thawing permafrost peatland (Stordalen Mire, 68°21’N, 19°02’E) and a temperate fen (Sallie’s Fen, 43°12.5′N, 71°3.5′W). At Stordalen Mire, I examined how lineage abundance and activity of methane oxidizing bacteria (MOB) vary with permafrost thaw. I found that MOB clustered across the thaw gradient according to their redox niches, and that MOB community composition was a strong predictor of CH4 oxidation rates. At Sallie’s Fen, I investigated belowground CH4 cycling across hummocks and lawns, and found that CH4 cycling in hummocks was more strongly regulated by CH4 oxidation whereas in lawns CH4 production was the more dominant process. This portion of my dissertation emphasizes the importance of considering site-scale landscape ...