Increased Soil Bacterial Abundance but Decreased Bacterial Diversity and Shifted Bacterial Community Composition Following Secondary Succession of Old-Field

Plant secondary succession is a very effective approach for the rejuvenation of degraded ecosystems. In order to comprehend alterations and driving mechanisms soil bacterial communities under old-field reveal their subsequent impacts on decomposition accumulation organic carbon (SOC) nitrogen (SON), we investigated changes in following ~160 years Loess Plateau China through analyses quantitative polymerase chain reaction (qPCR) Illumina MiSeq DNA sequencing 16S rRNA genes. Our results revealed that old-field, abundance progressively increased, while richness diversity significantly decreased. Principal component analysis Bray–Curtis similarity index showed community composition gradually shifted succession. Specifically, relative abundances Proteobacteria, Rokubacteria, Verrucomicrobia Actinobacteria Firmicutes slightly decreased The most enriched Proteobacteria (e.g., Rhizobiales, Xanthobacteraceae, Gammaproteobacteria, Bradyrhizobium, Rhizobiaceae, Mesorhizobiur) were found climax forest, Chloroflexi Gemmatimonadetes had lowest abundances. Further, members Actinobacteria, including Geodermatophilaceae, Frankiales, Blastococcus, Micrococcales, Micrococcacea, Propionibacteriales, Nocardioidaceae, Nocardioide, Streptomycetaceae, exhibited farmland stage. suggested greatly modified via transformation nutrients levels, altering plant biomass physiochemical properties. Soil was transformed from oligotrophic groups copiotrophic succession, which may promote SOC SON increasing utilization labile (C) (N), decreasing recalcitrant C N early- late-successional stages.