Effects of elevated atmospheric CO₂ concentration and warming on soil carbon pool and microbial community composition in a maize-grown Mollisol

In this study, we used the open top climate chamber (OTC) to simulate the long-term elevated atmospheric CO₂ concentration and warming. The soil samples were fractionated into cPOC (coarse particulate organic C), fPOC (fine particulate organic C) and MOC (mineral-associated organic C). The change of soil microbial community diversity was analyzed by 16SrRNA high-throughput sequencing, and the mechanism of long-term elevated atmospheric CO₂ concentration and warming on soil carbon conversion in dry farming soils was explained. The results showed that 12-yr consecutive climate change did not change the total soil organic carbon, but the turnover rate of soil organic carbon was significantly accelerated. Warming significantly increased fPOC, but decreased MOC. Long-term warming significantly increased the relative abundance of Bryobacter, and this genus was positively correlated with MOC. Long-term elevated atmospheric CO₂ concentration did not significantly change the contents of fPOC and MOC. Elevated atmospheric CO₂ concentration changed the soil microbial community, and significantly increased the abundance of Gram-negative bacteria Nitrospirae. Long-term elevated atmospheric CO₂ concentration and warming increases the turnover rate of SOC, while changes in community structure or genus abundance would further affect SOC stability.