Response of rhizosphere microbial communities to plant succession along a grassland chronosequence in a semiarid area

Purpose: Changes in microbial communities during natural succession in semiarid areas have been widely studied but their association with plant and soil properties remains elusive. In the present study, we investigated plant characteristics, rhizosphere soil variables, and microbial communities along a chronosequence of grasslands forming on abandoned farmland on the Chinese Loess Plateau. Materials and methods: Rhizosphere samples were collected from the early-stage dominant plant Artemisia capillaris from farmland abandoned for 5, 10, and 15 years and from the late-stage dominant plant Artemisia sacrorum from farmland abandoned for 10, 15, 20, and 30 years. Microbial community composition, including bacteria and fungi, was determined by high-throughput sequencing. Microbial succession rates represented by temporary turnover were assessed using the slope (w value) of linear regressions, based on log-transformed microbial community similarity over time. Results and discussion: Cover and aboveground biomass of A. capillaris tended to decrease, whereas those of A. sacrorum increased during the succession. Although the rhizosphere bacteria of A. capillaris transitioned from Proteobacteria-dominant to Actinobacteria-dominant, the bacteria of A. sacrorum exhibited the opposite trend. Bacterial and fungal community diversity tended to increase logarithmically with increasing plant aboveground biomass, indicating that an increase in plant biomass could lead to enhanced rhizosphere microbial diversity, but the rate of enhancement decreased gradually. A lower temporary turnover rate of bacterial and fungal communities in the rhizosphere than that in the bulk soil indicated a higher successional rate of the rhizosphere microbial community. Levels of soil nutrients, such as organic carbon, nitrate nitrogen, and ammonium nitrogen, were closely associated with the abundance and diversity of bacterial and fungal communities, indicating their critical role in shaping the rhizosphere microbial community. Conclusions: Our results indicate a close association between plant succession and rhizosphere microbial succession in a semiarid area. Plants affect the microbial communities possibly by changing the nutrient input into the rhizosphere.