Annual carbon sequestration and loss rates under altered hydrology and fire regimes in southeastern USA pocosin peatlands

• Published in: Global change biology Vol. 28; no. 21; pp. 6370 - 6384
• Main Authors: Richardson, Curtis J., Flanagan, Neal E., Wang, Hongjun, Ho, Mengchi
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.11.2022; Wiley-Blackwell
• Subjects: Annual; Bogs; Carbon dioxide; Carbon sequestration; Carbon sinks; Decomposition; eddy covariance; Emissions; Fire prevention; Gases; Greenhouse effect; greenhouse gas; Greenhouse gases; Groundwater table; Hydrology; Lakes; methane; Microorganisms; net ecosystem exchange; Net zero; Peat; Peatlands; pocosin; Restoration; Storage; Water depth; Water table; Water table depth; Wildlife; Wildlife refuges; United States > US
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.16366

Peatlands drained for agriculture or forestry are susceptible to the rapid release of greenhouse gases (GHGs) through enhanced microbial decomposition and increased frequency of deep peat fires. We present evidence that rewetting drained subtropical wooded peatlands (STWPs) along the southeastern USA coast, primarily pocosin bogs, could prevent significant carbon (C) losses. To quantify GHG emissions and storage from drained and rewetted pocosin we used eddy covariance techniques, the first such estimates that have been applied to this major bog type, on a private drained (PD) site supplemented by static chamber measurements at PD and Pocosin Lakes National Wildlife Refuge. Net ecosystem exchange measurements showed that the loss was 21.2 Mg CO2 ha−1 year−1 (1 Mg = 106 g) in the drained pocosin. Under a rewetted scenario, where the annual mean water table depth (WTD) decreased from 60 to 30 cm, the C loss was projected to fall to 2 Mg CO2 ha−1 year−1, a 94% reduction. If the WTD was 20 cm, the peatlands became a net carbon sink (−3.3 Mg CO2 ha−1 year−1). Hence, net C reductions could reach 24.5 Mg CO2 ha−1 year−1, and when scaled up to the 4000 ha PD site nearly 100,000 Mg CO2 year−1 of creditable C could be amassed. We conservatively estimate among the 0.75 million ha of southeastern STWPs, between 450 and 770 km2 could be rewet, reducing annual GHG emissions by 0.96–1.6 Tg (1 Tg = 1012 g) of CO2, through suppressed microbial decomposition and 1.7–2.8 Tg via fire prevention, respectively. Despite covering <0.01% of US land area, rewetting drained pocosin can potentially provide 2.4% of the annual CO2 nationwide reduction target of 0.18 Pg (1 Pg = 1015 g). Suggesting pocosin restoration can contribute disproportionately to the US goal of achieving net‐zero emission by 2050. Drainage of water from North Carolina coastal pocosin peatlands increases CO2 losses (a) as measured by eddy covariance, (b) results in annual losses of 21 metric tons of CO2 per hectare each year (c). When greenhouse gas (GHG) losses are assessed on drained peatlands across the SE USA millions of tons of CO2 are added to atmosphere each year through increased oxidation of peat or more rapidly through increased fire frequency (d), often with deep peat fires releasing catastrophic volumes of GHG. Rewetting of drained fallow peatlands is thus essential if the United States is to meet its GHG emission goals by 2050.