Characteristics of the soil microbial communities indicate the health of grasslands and quality of the environment. To elucidate the effects of desertification and artificial revegetation on the respective soil bacterial communities, four alpine grassland types including natural grassland (NG), desertified grassland (DG), grass-based artificial grassland (AG) and shrub-based
artificial grassland (AS) in a small watershed of Guinan County, Qinghai Province were selected and qPCR and Illumina MiSeq high-throughput amplicon sequencing technologies were used to study the variation between the communities in bacterial biomass, diversity and structure. We also analyzed the key factors shaping soil bacterial community structure and their contributions based on variations in vegetation and soil properties. It was found that grassland desertification significantly reduced bacterial community biomass and α diversity (P<0.05), but that bacterial community biomass could be almost restored to the level of undegraded grassland after 22 years of artificial revegetation. Desertification significantly increased the relative abundance of Gemmatimonadota, while abundance of Proteobacteria
and Planctomycetota significantly decreased (P<0.05). Artificial revegetation promoted the succession of dominant bacteria towards the community structure found in NG, and after 22 years of artificial revegetation, most of the bacterial relative abundances paralleled those of the undegraded status. Dissimilarity in bacterial community structure was noted between NG and DG, AG and AS, community structure in AG and AS were very similar. Soil bacterial community structure significantly positively correlated with the majority of vegetation and soil physiochemical properties (P<0.05). However, compared to soil physical (6.3%) and chemical (1.9%) properties, vegetation properties explained more variation (10.0%) in bacterial community structure. In total, the measured vegetation and soil indices explained 72.0% of variation in soil bacterial community structure, implying that vegetation and soil determine the shifts of soil bacterial community structure. Accordingly, it is essential and meaningful to strengthen vegetation and soil protection, and implement artificial revegetation in desertified grassland for protection and restoration of soil bacterial communities in Tibetan alpine grassland. However, the choice between shrub and grass planting during revegetation made little difference to the superficial soil bacterial community structure in artificial revegetation.