Extreme Drought Enhanced the Diversity and Network Complexity of Root-Associated Soil Fungal Components of a Native Grass (Achnatherum inebrians)

Achnatherum inebrians, a perennial grassland plant species, is often distributed in many semiarid regions of northwestern China and is well adapted to the abiotic stress (drought and low nutrient) conditions. Root-associated fungi had been reported to improve plant productivity and drought tolerance; in return, these host-associated and environmental factors also determined the assembly of root-associated fungi. A field experiment was performed to explore the effects of different (non, moderate and severe) drought levels on root-associated fungi, soil nutrients, grass biomass, and their relationships through amplicon sequencing of the 18S rDNA region. Drought increased the soil ammonium nitrogen, total nitrogen, and available phosphorus, while decreasing nitrate nitrogen and grass biomass of A. inebrians plants. The surrounding soil had significantly higher fungal diversity and richness than roots. Extreme drought treatment decreased soil fungal diversity, while increasing the diversity and complexity of fungi in roots of A. inebrians plants. Meanwhile, the increase of soil ammonium nitrogen and available phosphorus content in drought treatments also contributed to enhancing the root fungal diversity of A. inebrians plants. Soil fungal diversity and Glomeromycota abundance were positively related to the grass biomass. Extreme drought treatment promoted the colonization of fungi present in soil to roots of A. inebrians plants, enhancing fungal diversity and community complexity.