Effects of elevated atmospheric CO₂ concentrations on soil microorganisms

Effects of elevated CO₂ on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and synthesize results from studies assessing impacts of elevated CO₂ on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated CO₂ in atmosphere may enhance certain microbial processes such as CH₄ emission from wetlands due to enhanced carbon supply from plants. However, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of CO₂ fumigation systems are not fully understood.