Abstract: Soil microorganisms are important indicator for evaluating the effectiveness of vegetation restoration in karst ecosystems. However, the response of soil microbial communities to vegetation restoration remains uncertain due to the influence of biotic and abiotic factors. Whether soil physicochemical properties, as one of the main factors affecting the habitat of bacteria, can be directly used to infer variations in soil bacterial communities associated with land use changes in karst ecosystems remains unclear. Here we collected soil samples of surface layer (0-10 cm depth) from Zanthoxylum bungeanum forest and secondary forest in the rocky desertification area of Huajiang Karst Canyon, Guizhou, as well as cropland as a control. By using high-throughput 16S rRNA gene sequencing technology, we examined the effects of afforestation on soil properties, soil bacterial community composition, and diversity in karst rocky desertification area, as well as the main factors affecting soil bacterial community after afforestation. The results showed that the main dominant phyla of soil bacteria in all samples were Acidobacteriota, Actinobacteriota, Proteobacteria, and Chloroflexi. Afforestation significantly altered the abundance but not alpha diversity of soil bacteria. After cropland was converted to Zanthoxylum bungeanum forest and secondary forest, the relative abundance of Acidobacteriota and Actinobacteriota significantly increased, while that of Proteobacteria significantly decreased. Chloroflexi had the highest abundance in Zanthoxylum bungeanum forest. Afforestation reduced the abundance of significantly enriched bacteria and changed the type of enriched bacteria. Redundancy analysis showed that soil pH, exchangeable calcium, organic carbon, water content, bulk density, and soil silt content jointly affected bacterial community structure, with exchangeable calcium having the highest degree of influence. These results indicated that the potential interaction between soil physicochemical properties and bacterial communities may jointly affect soil bacterial community structure after afforestation in karst canyon areas.

Key words: afforestation, exchangeable Ca, soil bacterial community, karst rocky desertification