Abstract
Abstract. Wetland loss and climate change are known to alter regional and global methane (CH4) budgets. Over the last six decades, an extensive area of marshland has been converted to cropland on the Sanjiang Plain in northeast China, and a significant increase in air temperature has also been observed there, while the impacts on regional CH4 budgets remain uncertain. Through model simulation, we estimated the changes in CH4 emissions associated with the conversion of marshland to cropland and climate change in this area. Model simulations indicated a significant reduction of 1.1 Tg yr−1 (0.7–1.8 Tg yr−1) from the 1950s to the 2000s in regional CH4 emissions. The cumulative reduction of CH4 from 1960 to 2009 was estimated to be ~36 Tg (24–57 Tg) relative to the 1950s, and marshland conversion and the climate contributed 86% and 14% of this change, respectively. Interannual variation in precipitation (linear trend with P > 0.2) contributed to yearly fluctuations in CH4 emissions, but the relatively lower amount of precipitation over the period 1960–2009 (47 mm yr−1 lower on average than in the 1950s) contributed ~91% of the reduction in the area-weighted CH4 flux. Global warming at a rate of 0.3 ° per decade (P < 0.001) has increased CH4 emissions significantly since the 1990s. Relative to the mean of the 1950s, the warming-induced increase in the CH4 flux has averaged 19 kg ha−1 yr−1 over the last two decades. In the RCP (Representative Concentration Pathway) 2.6, RCP 4.5, RCP 6.0 and RCP 8.5 scenarios of the fifth IPCC assessment report (AR5), the CH4 fluxes are predicted to increase by 36%, 52%, 78% and 95%, respectively, by the 2080s compared to 1961–1990 in response to climate warming and wetting.
Highlights
Methane (CH4) is recognized as one of the most potent greenhouse gases; it is 25 times more powerful than carbon dioxide (CO2) in terms of its global warming potential (IPCC, 2007)
Recognizing the significance of wetlands in regional CH4 budgets, this study focuses on quantifying the variation in CH4 emissions on the Sanjiang Plain of northeast China via model simulations
CH4MODwetland coupled with the empirical water table model can basically simulate the seasonal variations in standing water depth (Fig. E1a and b) and CH4 fluxes (Fig. E1c and d)
Summary
Methane (CH4) is recognized as one of the most potent greenhouse gases; it is 25 times more powerful than carbon dioxide (CO2) in terms of its global warming potential (IPCC, 2007). The regional and global CH4 budgets of wetlands are influenced by large-scale processes, such as the conversion of wetlands to other uses (Bridgham et al, 2006; Huang et al, 2010) and climate change (Cao et al, 1998; Gedney et al, 2004; Shindell et al, 2004). In terms of temperature (Charmann and Hendon, 2000) and precipitation (Cao et al, 1998; Charmann and Hendon, 2000; Vepraskas and Caldwell, 2008), alters the biochemical processes involved in CH4 production, oxidation and emission (Strack et al, 2008; Updegraff et al, 2001)
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