The shift of carbon metabolic pathways mediated by key rhizosphere microbes of exotic plants affects organic carbon

Exotic plant invasion often drives soil microorganisms to affect soil organic carbon (SOC), whereas microbial taxa that played a key role in the SOC changes and the related mechanisms remain unclear.

In this study, a long-term simulation of the invasion process of exotic plants, Ambrosia artemisiifolia and Bidens pilosa, was carried out to evaluate the relationships between soil microorganisms and SOC during the invasion of exotic plants. A metagenomic method was conducted to study the microbial communities and carbon metabolic pathways in the rhizosphere soil.

Our results showed that the invasion of two exotic plants significantly increased the concentrations of soil microbial biomass carbon (MBC) and SOC by shifting carbon metabolic pathways mediated by key microbial taxa. The dominant carbon metabolic pathways were transformed into the tricarboxylic acid cycle, glyoxylate and dicarboxylate metabolism, and dicarboxylate-hydroxybutyrate cycle in the rhizosphere soil of two exotic species after long-time interaction, and these three pathways were closely correlated to Bradyrhizobium, Mycobacterium, and Sphingomonas. The structural equation model revealed that the invasion of A. artemisiifolia and B. pilosa were more likely to affect the SOC via affecting MBC concentration rather than directly affecting SOC, suggesting MBC played a key role in SOC accumulation in the exotic plant’s rhizosphere.

The similar microbial mechanism of SOC in two exotic species, suggests that exotic plant invasion may affect the SOC cycle by adjusting soil microbiota and microbial metabolic activities.