Higher temporal turnover of soil fungi than bacteria during long-term secondary succession in a semiarid abandoned farmland

Abstract

Microorganisms play critical roles in soil biogeochemical processes and the establishment of vegetation communities. However, their long-term successional patterns and associations with environmental factors are not well understood, especially in semiarid areas where plant community composition and species diversity change rapidly. We investigated changes in soil (Cambisol) microbial communities across a chronosequence of abandoned farmland comprising six successional stages (0, 11, 35, 60, 100, and 150-years) in the semiarid Loess Plateau of China. We aimed to reveal the long-term patterns and succession rates of microbial communities, and to reveal the driving forces. Bacterial and fungal communities were characterized by sequencing bacterial 16S ribosomal RNA genes and fungal internal transcribed spacers (ITS), respectively. Temporal turnover of microbial succession was investigated using the slope (w value) of linear regression of log-transformed microbial community similarity over time. Succession rate of fungi was approximately three times higher (w = 0.1477, P < 0.0001) than that of bacteria (w = 0.0549, P < 0.0001). Bacterial succession was affected by changes in soil NH4+-N, total N, organic C, water content, bulk density, and pH, whereas fungi were more susceptible to changes in NO3−-N, available phosphorus, and C:N ratio. Bacterial communities transitioned from slow-growing oligotrophic groups (Gemmatimonadetes, Chloroflexi) to fast-growing copiotrophic groups (Alpha- and Betaproteobacteria). Basidiomycota showed the highest temporal turnover (w = 0.2000, P < 0.0001), followed by Armatimonadetes, Firmicutes, Verrucomicrobia, Chloroflexi, and Proteobacteria. These results provide new insights into microbial community dynamics during long-term secondary succession, and enhance our understanding of associations between soil factors and microbes in semiarid ecosystems.