Effects of Drought on the Growth of Lespedeza davurica through the Alteration of Soil Microbial Communities and Nutrient Availability

Lespedeza davurica (Laxm.) is highly important for reducing soil erosion and maintaining the distinctive natural scenery of semiarid grasslands in northwest China. In this study, a pot experiment was conducted to investigate the effects of drought (20% water-holding capacity) on biomass and its allocation, root characteristics, plant hormones, and soil microbial communities and nutrients after L. davurica was grown in a greenhouse. Drought reduced the total biomass of L. davurica but increased the root:shoot biomass ratio. In addition, drought altered the composition and structure of microbial communities by limiting the mobility of nutrients in non-rhizosphere soils. In particular, drought increased the relative abundances of Basidiomycota, Acidobacteria, Actinobacteria, Coprinellus, Humicola and Rubrobacter, which were closely positively related to the soil organic carbon, pH, available phosphorus, ammonia nitrogen (N) and nitrate N under drought conditions. Furthermore, soil fungi could play a more potentially significant role than that of bacteria in the response of L. davurica to drought. Consequently, our study uncovered the effects of drought on the growth of L. davurica by altering soil microbial communities and/or soil nutrients, thus providing new insights for forage production and natural grassland restoration on the Loess Plateau of China.