Analysis of methane emission characteristics and environmental response in natural wetlands

Abstract

Wetlands are the most important natural source of methane (CH4) emissions. Apparent wetland CH4 emissions depend largely on the balance between CH4 production and oxidation. Wetland plants play an important role in all processes. However, direct observations and side-by-side comparisons of CH4 emissions from wetlands with different vegetation types are lacking at the global scale. There is still a lack of clarity in characterizing the environmental response to CH4 emissions from wetlands with different vegetation types. Based on the FLUXNET-CH4 dataset and the Global Standard Soil Database, we analyzed the environmental response characteristics of CH4 emissions and clarified the important role of plants in CH4 emissions. We categorized wetlands into vascular plant wetlands (VPWs) and moss plant wetlands (MPWs). VPWs CH4 emissions were typically higher and more heterogeneous, whereas MPWs CH4 emissions were lower and less variable. When the water table is below the surface, VPWs still have high CH4 emission rates, while MPWs have CH4 emission rates close to zero. In addition, the temperature sensitivity of CH4 emissions from VPWs (Q10 = 2.26) is significantly higher than that of MPWs (Q10 = 1.71). Solar radiation was the main factor affecting CH4 emissions from VPWs, and temperature was the main factor affecting CH4 emissions from MPWs. Finally, our results of structural equation model suggested that soil and water environment, temperature, and plants all contribute to wetland CH4 emissions to varying degrees. These findings highlight the important role of wetland vegetation in CH4 emissions, which should be seriously considered to reduce uncertainty in the assessment of wetland CH4 emissions.