Rhizosphere soil microbial properties on abandoned croplands in the Loess Plateau, China during vegetation succession.

摘要

Rhizosphere is a microbiosphere with chemical, physical, and biological properties different from those of bulk soils. Knowledge of the changes in the microbial properties of plant rhizospheres is important in understanding the interactions between soil and plant communities. The present study aims to investigate the effect of bulk and rhizosphere soils on the microbial properties of eight croplands abandoned for 1, 3, 5, 10, 13, 15, 20, and 30 years and to evaluate the change in the rhizosphere soil microbial properties with time in the Loess Plateau, China. The results show that during the succession on the abandoned croplands, the pioneer species, Artemisia capillaries Thunb, was an important species in the 1- to 13-year sites, whereas the late species, Artemisia sacrorum Ledeb, emerged into the community after 13 years and became the dominant community species in 30 years. The species richness of the community exhibited an increasing trend during the first 15 years, and rapidly decreased thereafter. The organic carbon, total nitrogen, microbial biomass carbon, and microbial biomass nitrogen contents in the rhizosphere soil increased compared with those in bulk soil. Basal respiration and saccharase, alkaline phosphatase, catalase, and peroxidase activities were also enhanced, and the pH value decreased. Compared with the companion species, the dominant species showed higher organic carbon, total nitrogen, microbial biomass carbon, and microbial biomass nitrogen contents as well as enhanced respiration, but no significant difference in urease, catalase, alkaline phosphatase, and peroxidase activities was observed. As the succession proceeded, both A. capillaries and A. sacrorum showed increased microbial biomass carbon and microbial biomass nitrogen, and a decreased metabolic quotient. The soil enzymes of these two species behaved differently. Coverage and aboveground biomass of A. capillaries and A. sacrorum exhibited different relationships with microbial biomass and enzymes. In conclusion, the soil microbial activity in the rhizosphere is affected by plants, the soil condition, and the successional stage. Plant root exudates play an important role in the change in rhizosphere microbial properties.