Change in soil bacterial community during secondary succession depend on plant and soil characteristics

Secondary succession has great impact on plant and soil characteristics, however, the trends of microbial patterns and the influencing factors during grassland succession without human disturbance remains unclear. Therefore, we investigated the changes of bacterial community in sloped farmlands abandoned for 0, 20, 30, and 40 years (GL-0 yr, GL-20 yr, GL-30 yr, and GL-40 yr). Additionally, plant traits (coverage, diversity, richness, evenness, biomass, and biomass carbon) and soil nutrients were also determined. The results showed that soil bacterial alpha diversity was positively and significantly correlated with the succession time, and the secondary succession greatly affected soil bacterial beta diversity, in contrast, the effects on soil bacterial beta diversity at the late succession time (GL40 and GL30) were larger than that at the early succession time (GL20). For the bacterial taxa, the dominant phyla including Actinobacteria (34.8%), Proteobacteria (26.0%), Acidobacteria (15.0%), Chloroflexi (7.5%), Gemmatimonadetes (8.7%), Nitrospirae (1.6%), Bacteroidetes (2.1%), Verrucomicrobia (1.1%), and Planctomycetes (1.0%) were found. Particularly, the relative abundance of Proteobacteria was higher at the late time (RP40), while the Actinobacteria was higher at the early time (RP20). Such different responses of bacterial diversity and taxa were largely explained by plant traits and soil nutrients, especially for TOC and TN. Collectively, our results indicate that plant secondary succession shifts the bacterial community structure, largely driven by changes in soil nutrients and plant diversity and composition, and also supported the growing view that soil bacterial community are the key determinants of aboveground and belowground linkages that functionally control terrestrial ecosystems.