Methane emissions associated with the conversion of marshland to cropland and climate change on the Sanjiang Plain of northeast China from 1950 to 2100

[摘要] Wetland loss and climate change are known to alter regional and globalmethane (CH₄) budgets. Over the last six decades, an extensive area ofmarshland has been converted to cropland on the Sanjiang Plain in northeastChina, and a significant increase in air temperature has also been observedthere, while the impacts on regional CH₄ budgets remain uncertain.Through model simulation, we estimated the changes in CH₄ emissionsassociated with the conversion of marshland to cropland and climate changein 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 regionalCH₄ emissions. The cumulative reduction of CH₄ from 1960 to 2009was estimated to be ~36 Tg (24–57 Tg) relative to the 1950s,and marshland conversion and the climate contributed 86% and 14% ofthis change, respectively. Interannual variation in precipitation (lineartrend with P > 0.2) contributed to yearly fluctuations in CH₄emissions, but the relatively lower amount of precipitation over the period1960–2009 (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) hasincreased CH₄ emissions significantly since the 1990s. Relative to themean of the 1950s, the warming-induced increase in the CH₄ flux hasaveraged 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 assessmentreport (AR5), the CH₄ fluxes are predicted to increase by 36%,52%, 78% and 95%, respectively, by the 2080s compared to 1961–1990in response to climate warming and wetting.

[学科分类] 地球化学与岩石