A microbial functional group‐based module for simulating methane production and consumption: Application to an incubated permafrost soil

Abstract

Abstract Accurately estimating methane (CH 4 ) flux in terrestrial ecosystems is critically important for investigating and predicting biogeochemistry‐climate feedbacks. Improved simulations of CH 4 flux require explicit representations of the microbial processes that account for CH 4 dynamics. A microbial functional group‐based module was developed, building on the decomposition subroutine of the Community Land Model 4.5 . This module considers four key mechanisms for CH 4 production and consumption: methanogenesis from acetate or from single‐carbon compounds and CH 4 oxidation using molecular oxygen or other inorganic electron acceptors. Four microbial functional groups perform these processes: acetoclastic methanogens, hydrogenotrophic methanogens, aerobic methanotrophs, and anaerobic methanotrophs. This module was used to simulate dynamics of carbon dioxide (CO 2 ) and CH 4 concentrations from an incubation experiment with permafrost soils. The results show that the model captures the dynamics of CO 2 and CH 4 concentrations in microcosms with top soils, mineral layer soils, and permafrost soils under natural and saturated moisture conditions and three temperature conditions of −2°C, 3°C, and 5°C ( R 2 > 0.67; P < 0.001). The biases for modeled results are less than 30% across the soil samples and moisture and temperature conditions. Sensitivity analysis confirmed the importance of acetic acid's direct contribution as substrate and indirect effects through pH feedback on CO 2 and CH 4 production and consumption. This study suggests that representing the microbial mechanisms is critical for modeling CH 4 production and consumption; it is urgent to incorporate microbial mechanisms into Earth system models for better predicting trace gas dynamics and the behavior of the climate system.