Keqi He, Wenhong Li, Yu Zhang, Angela Zeng, Inge E. M. de Graaf, Maricar Aguilos, Ge Sun, Steven G. McNulty, John S. King, Neal E. Flanagan, Curtis J. Richardson
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引用次数: 0
Abstract
Wetlands are the largest and most climate-sensitive natural sources of methane. Accurately estimating wetland methane emissions involves reconciling inversion (“top-down”) and process-based (“bottom-up”) models within the global methane budget. However, estimates from these two model types are inherently interdependent and often reveal substantial discrepancies. To enhance the reliability of both approaches, we need a comprehensive understanding of wetland methane emissions and an independent high-resolution long-term flux data set. Here, we employed a data-driven random forest approach to identify key variables influencing methane emissions from subtropical freshwater wetlands in the Southeastern United States. The model-estimated monthly mean methane fluxes fit well with measured methane fluxes (R2 = 0.67) at four representative FLUXNET-CH4 wetland sites across the region. Variable importance analysis highlighted the sensitivity of subtropical freshwater wetland methane emissions to variations in both temperature and water levels. High temperatures facilitate methanogenesis by enhancing microbial activities, while elevated water levels maintain anaerobic conditions necessary for methane production. Notably, the response of methane emissions to water level fluctuations is contingent on temperature conditions, and vice versa. Moreover, we constructed the first high-spatial-resolution (∼1 km × 1 km) and long-term (1982–2010) gridded regional wetland methane flux product for the Southeastern United States, estimating annual methane emissions from subtropical freshwater wetlands in the region at 4.93 ± 0.11 Tg CH4 yr−1 for 1982–2010. This new benchmark product holds promise for validating and parameterizing uncertain wetland methane emission processes in bottom-up models and provides improved prior information for top-down models.
期刊介绍:
Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.