Increased precipitation, rather than warming, exerts a strong influence on arbuscular mycorrhizal fungal community in a semiarid steppe ecosystem

Knowing the responses of arbuscular mycorrhizal (AM) fungi to warming and increased precipitation are critical for understanding how biodiversity is maintained and how the ecosystem functions under global climate-change scenarios in natural ecosystems. In this study, AM fungal communities were examined in a 6 year experiment with warming and increased precipitation, in a semiarid steppe in northern China. Only the increased precipitation, regardless of warming, significantly increased AM fungal extra-radical hyphal density, compared with the control treatment. AM fungal spore density was significantly increased by the combination of warming and increased precipitation, and increased precipitation-only treatments, but not by warming alone. A total of 36 operational taxonomic units (OTUs) of AM fungi were recovered by 454 pyrosequencing of 18S rDNA. Only increased precipitation, regardless of warming, significantly decreased AM fungal OTU richness and Shannon diversity index, and yet significantly increased AM fungal Bray-Curtis dissimilarity index, compared with the control treatment. AM fungal community composition was significantly affected by increased precipitation via water availability, but not by warming. Our findings demonstrated that the AM fungal community responded more strongly to water availability than to warming in the semiarid steppe ecosystem.