Abstract
Northern peatlands constitute a significant source of atmospheric methane (CH 4). However, management of undisturbed peatlands, as well as the restoration of disturbed peatlands, will alter the exchange of CH 4 with the atmosphere. The aim of this systematic review and meta‐analysis was to collate and analyze published studies to improve our understanding of the factors that control CH 4 emissions and the impacts of management on the gas flux from northern (latitude 40° to 70°N) peatlands. The analysis includes a total of 87 studies reporting measurements of CH 4 emissions taken at 186 sites covering different countries, peatland types, and management systems. Results show that CH 4 emissions from natural northern peatlands are highly variable with a 95% CI of 7.6–15.7 g C m−2 year−1 for the mean and 3.3–6.3 g C m−2 year−1 for the median. The overall annual average (mean ± SD) is 12 ± 21 g C m−2 year−1 with the highest emissions from fen ecosystems. Methane emissions from natural peatlands are mainly controlled by water table (WT) depth, plant community composition, and soil pH. Although mean annual air temperature is not a good predictor of CH 4 emissions by itself, the interaction between temperature, plant community cover, WT depth, and soil pH is important. According to short‐term forecasts of climate change, these complex interactions will be the main determinant of CH 4 emissions from northern peatlands. Drainage significantly (p < .05) reduces CH 4 emissions to the atmosphere, on average by 84%. Restoration of drained peatlands by rewetting or vegetation/rewetting increases CH 4 emissions on average by 46% compared to the original premanagement CH 4 fluxes. However, to fully evaluate the net effect of management practice on the greenhouse gas balance from high latitude peatlands, both net ecosystem exchange (NEE) and carbon exports need to be considered.
Highlights
The concentration of methane (CH4) in the atmosphere has increased from 722 ppb during the pre-industrial period to 1,819 ppb in 2012, due to increased anthropogenic emissions (Ciais et al, 2013; Whalen, 2005)
The specific hypotheses that we tested were as follows: (1) Methane emission is mainly controlled by water table (WT), plant community, temperature, and pH; (2) management, especially drainage and restoration, significantly affects CH4 emissions; and (3) climate change will significantly reduce the capacity of northern peatlands to absorb the atmospheric C
Our analysis suggests that the emission of CH4 from northern peatlands is mainly controlled by WT depth (Granberg et al, 1997; Moore & Knowles, 1989), plant community composition (Granberg et al, 1997; Nilsson et al, 2001), and soil pH (Hutsch, 1998; Singh et al, 1999)
Summary
The concentration of methane (CH4) in the atmosphere has increased from 722 ppb during the pre-industrial period to 1,819 ppb in 2012, due to increased anthropogenic emissions (Ciais et al, 2013; Whalen, 2005). Methane production by methanogenic archaea could be inhibited by the transport of O2 into otherwise anaerobic layers, or oxidized due to release of O2 into the rhizosphere Due to this bypass release of CH4, the net emission to the atmosphere tends to increase when aerenchymatous vascular plants are present (Joabsson et al, 1999). The specific hypotheses that we tested were as follows: (1) Methane emission is mainly controlled by WT, plant community, temperature, and pH; (2) management, especially drainage and restoration, significantly affects CH4 emissions; and (3) climate change will significantly reduce the capacity of northern peatlands to absorb the atmospheric C
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