Enhanced CO₂ emissions from soil organic matter in agricultural fields during microbial community assemblage

Using two kinds of microbial inoculations extracted from soil cropped to rice and peanut, we conducted a swap-inoculation experiment to explore the relative importance of microbial inoculation and soil properties on CO₂ emissions from soil. Inoculated microorganisms into a soil different from their origin (swap inoculation) were partially successful and reduced CO₂ emissions, namely according to home-field advantage (HFA); The success of invasive microorganisms depended on molecular composition of soil organic matter (SOM) compared to inoculation of native microbes (inoculated microorganisms into origin soil). The different habits screened the fewer microorganisms to undergo respiration for energy and life-sustaining activities, thus decreasing CO₂ emissions from SOM. However, the effect of HFA diminished with incubation time, as the invasive microorganisms reshaped SOM molecular diversity and composition during microbial community assemblage, which fits with the Gaia effect (GE). Specific microbial communities, such as Bacteroidetes and Actinobacteria, drove the conversion of persistent molecules to labile molecules, thereby increasing the chances of SOM mineralization by microorganisms. We found there was positive correlation between labile SOM molecules and SOM mineralization. In addition, MBC increased in swap inoculation compared to native inoculation after 60 days, which also resulted in higher CO₂ emissions from SOM. HFA and GE provide new perspectives to help decipher the interaction between microorganisms and the habitat under microbial invasion, and the mechanism of influence on CO₂ emissions from SOM.