Microbial diversity drives carbon use efficiency in a model soil

Empirical evidence for the response of soil carbon cycling to the combined effects of warming, drought and diversity loss is scarce. Microbial carbon use efficiency (CUE) plays a central role in regulating the flow of carbon through soil, yet how biotic and abiotic factors interact to drive it remains unclear. Here, we combined distinct community inocula (biotic factor) with different temperature and moisture conditions (abiotic factors) to manipulate microbial diversity and community structure within a model soil system. Abiotic factors indirectly influenced CUE through their impacts on diversity and community structure, which were the strongest predictors of CUE. We also found that abiotic factors modulated the relationship between diversity and CUE, with CUE being positively correlated with bacterial diversity under high moisture. Altogether these results indicate that drier soils diminished the synergistic effect between diversity and CUE, with potential consequences for the fate of C in soils.