Distinctive pattern and mechanism of precipitation changes affecting soil microbial assemblages in the Eurasian steppe

Precipitation may increase or decrease by different intensities, but the pattern and mechanism of soil microbial community assembly under various precipitation changes remain relatively underexplored. Here, although ±30% precipitation caused a small decrease (∼19%) in the within-treatment taxonomic compositional dissimilarity through the deterministic competitive exclusion process in a steppe ecosystem, ±60% precipitation caused a large increase (∼35%) in the dissimilarity through the stochastic ecological drift process (random birth/death), which was in contrast with the traditional thought that increasing the magnitude of environmental changes (e.g., from +30% to +60%) would elevate the importance of deterministic relative to stochastic processes. The increased taxonomic dissimilarity/stochasticity under ±60% precipitation translated into functional dissimilarity/stochasticity at the gene, protein, and enzyme levels. Overall, our results revealed the distinctive pattern and mechanism of precipitation changes affecting soil microbial community assembly and demonstrated the need to integrate microbial taxonomic information to better predict their functional responses to precipitation changes.