Abstract: Under-forest economy has become an important way to increase forest output and promote forestry economic benefit. The objective of this study was to identify changes in soil bacterial community diversity and structure in Corydalis yanhusuo(an earlyspring medicinal plant) rhizosphere associated with moso bamboo forest gaps. We collected C. yanhusuo rhizosphere soil samples from plots located in large (400 m²), medium (100 m²), and small forest gaps (25 m²), as well as from the closed stands. Highthroughput sequencing combined with habitat parameters were used to analyze the variations of soil bacterial community diversity and structure among these plots. The results showed that the soil bacterial communities in the four plots contained 35 phyla, 104 classes, 195 orders, 321 families, and 523 genera. Although the specific rankings of the dominant groups in the soil bacterial communities of large and medium forest gaps were different, Acidobacteria and Proteobacteria were overall the most dominant taxa, followed by Chloroflexi and Actinobacteria. In small forest gaps and closed stands, Proteobacteria were dominant, followed by Actinobacteria and Bacteroidetes, while Acidobacteria was the least dominant. With the decrease of forest gap size, the relative light intensity dropped to 10.7%-22.5% of full light. The total number of taxa in bacterial communities tended to decrease, and species abundance and specificity, phylogenetic diversity, community diversity, and community evenness all decreased with the decreases of gap size. However, the closedstand habitat was better than the small forest gaps. The operational taxonomic unit (OTU) percentages of bacterial communities at the phylum and genus levels were significantly correlated with light intensity and air temperature, but showed opposite relationship with soil moisture content and air humidity, and had no correlation with forest gap size, altitude and border bamboo parameters. Therefore, large forest gaps were the best one favoring the development of C. yanhusuorhizosphere bacterial communities, while small forest gaps were not suitable for them. Forest gaps and closedstand habitats can provide growth opportunities for different bacterial communities under certain conditions. Consequently, soil microbiological indicators, such as representative communities, can be used as indicators of changes in the development of forest gaps. Relative light intensity and air temperature have great impacts on rhizosphere soil bacterial communities during the artificial creation of forest gaps and cultivation of C. yanhusuo, which are important in regulating soil bacterial community structure and promoting the stability of soil ecosystems.

Key words: irrigation and nitrogen, microbial diversity, microbial biomass carbon and nitrogen.