Effect of different factors dominated by water level environment on wetland carbon emissions.

The exacerbation of global warming has led to changes in wetland carbon emissions worldwide. Therefore, we conducted a meta-analysis of methane (CH) and carbon dioxide (CO) emissions in wetland ecosystem and explored the underlying mechanisms. Our finding indicated that (1) water level of -50 to 30 cm (the negative value represents the depth of the groundwater table, whereas the positive value represents the height of the above-ground water table) and -10 cm will result in a large CH and CO emissions, respectively; (2) CO and CH massive emissions occurred at the temperature range of 15-20 °C and > 20 °C, respectively; (3) CH and CO emissions were higher when the mean annual precipitation (MAP) was between 400 and 800 mm, but lower at an range of 800-1200 mm; (4) there was no significant difference in CH and CO emissions in marsh over time; however, CO emissions in fen were relatively high; (5) there was no significant difference in CO emissions between the forest, grass, and shrub groups; there was also no significant difference in CH emission within the forest group; and (6) MAP has a low impact (0.577) on the CO emissions of wetlands. Collectively, our findings highlight the characteristics of wetland CH and CO emissions under different conditions dominated by water level, enhance our understanding of the potential mechanisms that govern these effects, and provide basis for future wetland management and restoration in the future.