A review of the mechanisms and controlling factors of methane dynamics in forest ecosystems

It is widely recognized that forest soils are important terrestrial sinks for atmospheric CH4; however, the complexity of the underlying microbial production and oxidation processes, forest ecosystem CH4 fluxes, and the links to environmental controls are not well understood. Several studies have shown that forests have high CH4 emission rates under certain environmental conditions. In this paper, we reviewed the CH4 production mechanisms and monitored CH4 produced by the CO2-reducing pathway, methylotrophic pathway, and aceticlastic pathway. In recent years, CH4 flux monitoring methods in forest ecosystems have included chamber-gas chromatography (C-GC) method, eddy covariance (EC) method, relaxed eddy accumulation (REA) method, and flux-gradient (FG) method. CH4 emissions may be influenced by various operating parameters and environmental conditions. Water balance, one of the main controlling factors affecting CH4 emissions in forest ecosystems, creates a necessary anaerobic environment for the production of CH4. CH4 gas dynamics are mainly influenced by human and natural disturbances, especially disturbances caused by climate change. CH4 dynamics in forest ecosystems are influenced by soil moisture, soil nutrients such as C, N, and P, natural disturbances such as droughts and fires, and forest management practices such as thinning and understory removal. To ensure a more accurate simulation and assessment of global CH4 production and consumption, forest CH4 fluxes should be included in the global CH4 budget under the context of global change.