Arbuscular mycorrhizal (AM) fungi significantly affect plant interactions and community composition both in semi-arid Loess Plateau and Tibetan alpine grasslands, and are believed to modulate plant community dynamics under future climate change scenarios. However, it remains unclear whether AM fungal communities respond to the ongoing climate change drivers with similar patterns between these contrasting systems. We examined the impact of warming and precipitation alteration (+ or – 30%) on the taxonomic and phylogenetic composition of soil AM fungal communities in two 4-yr field manipulation studies, one each in a Loess grassland and a Tibetan alpine meadow. AM fungal abundance was quantified by determining the content of AM fungal signature phospholipid fatty acid (16: 1ω5c), and AM fungal communities were characterized with high resolution amplicon sequencing (Illumina, MiSeq). Phylogenetic patterns were then used to infer the ecological processes structuring communities.
Results/Conclusions
Results showed that both the initial AM fungal communities and their responses to warming and rainfall changes were significantly different between two grasslands. Warming significantly reduced AM fungal biomass in the Loess but not the Meadow soil, although it decreased the evenness in both grasslands. In contrast, altered precipitation increased AM fungal biomass in the Meadow but not the Loess soil. Surprisingly, neither warming nor precipitation change significantly affected the community composition of AM fungi in the Loess soil. However, warming significantly altered the community composition in the Meadow soil, reducing Glomeraceae but increasing Claroideoglomeraceae and Diversisporaceae. In addition, soil AM fungal communities significantly differed between two soils. In the Loess soil, communities were phylogenetically over-dispersed across all experimental treatments, suggesting that competitive exclusion was the primary driver of community assembly. In the Meadow soil, in contrast, communities were phylogenetically random in un-warming plots and over-dispersed in warming plots, suggesting that the ecological process structuring communities shifted from a stochastic process to competitive exclusion under climate warming. Taken together, our findings suggest that processes that dominantly affect the structures of AM fungal communities and mediate their responses to climate change factors may strongly depend on local plant and environmental conditions.