Population turnover promotes fungal stability in a semi-arid grassland under precipitation shifts

Abstract

Abstract Aims Bacteria and fungi are two primary groups of soil microbes, and their stability determines the persistence of microbial functions in response to a changing environment. Recent studies reported higher fungal than bacterial stability under precipitation alteration, the underlying mechanisms, however, remain elusive. Methods A 3-year precipitation manipulation experiment in a semi-arid grassland was used to compare the bacterial and fungal diversities, including alpha diversity, beta diversity and microbial community composition turnover, in response to precipitation manipulations. A framework is proposed to understand the stability properties of bacteria and fungi under precipitation alteration. We conceived a diagrammatic valley to illustrate microbial stability with the depth representing resistance and the width ecological resilience. Important Findings We found that ±60% in precipitation significantly reduced the richness and increased the evenness of bacteria but had trivial impacts on fungi. Precipitation alteration yielded stronger impacts on the variation in alpha diversity of bacteria than fungi, suggesting that the bacterial community is more sensitive to water stress than the fungal community. Moreover, fungi had wider composition turnover than that of bacteria, indicating higher composition variation of fungi than bacteria. The population turnover of fungi, reflected by composition variation, coefficient variation of diversity index and composition turnover, was larger than that of bacteria at both temporal and spatial scales, indicating the population turnover promotes fungal stability. The higher stability of fungal community in tolerating water stress is analogous to a ball in a wide valley that swing substantially but remain close to its steady state; while the lower stability of bacteria community is analogous to a ball that swings slightly but stay far away from its steady state. Our finding that the fungal community had higher stability than bacterial community in a semi-arid grassland might be applicable to other biomes.