A Microbial Functional Group‐Based CH<sub>4</sub> Model Integrated Into a Terrestrial Ecosystem Model: Model Structure, Site‐Level Evaluation, and Sensitivity Analysis
Chaoqing Song, Junwei Luan, Xiaofeng Xu, Minna Ma, Mika Aurela, Annalea Lohila, Ivan Mammarella, Pavel Alekseychik, Eeva‐Stiina Tuittila, Wei Gong, Xiuzhi Chen, Xianhong Meng, Wenping Yuan
Abstract
Abstract Wetlands are one of the most important terrestrial ecosystems for land‐atmosphere CH 4 exchange. A new process‐based, biophysical model to quantify CH 4 emissions from natural wetlands was developed and integrated into a terrestrial ecosystem model (Integrated Biosphere Simulator). The new model represents a multisubstance system (CH 4 , O 2 , CO 2 , and H 2 ) and describes CH 4 production, oxidation, and three transport processes (diffusion, plant‐mediated transport, and ebullition). The new model uses several critical microbial mechanisms to represent the interaction of anaerobic fermenters and homoacetogens, hydrogenotrophic, and acetoclastic methanogens, and methanotrophs in CH 4 production and oxidation. We applied the model to 24 different wetlands globally to compare the simulated CH 4 emissions to observations and conducted a sensitivity analysis. The results indicated that (1) for most sites, the model was able to capture the magnitude and variation of observed CH 4 emissions under varying environmental conditions; (2) the parameters that regulate dissolved organic carbon and acetate production, and acetoclastic methanogenesis had the significant impact on simulated CH 4 emissions; (3) the representation of the process components of CH 4 cycling showed that CH 4 oxidation was about half or more of CH 4 production, and plant‐mediated transport was the dominant pathway at most sites; and (4) the seasonality of simulated CH 4 emissions can be controlled by soil temperature, water table position, or combinations thereof.