Abstract: Soil bacteria are an important part of the microbial community. Previous studies on soil bacteria along elevational gradients have mainly focused on different vegetation types and ecosystems with great differences. However, the distribution of soil bacterial community diversity, structure, and function of the same vegetation type along an elevational gradient remains to be explored, and the relationship between soil bacterial community structure and function is unclear. In this study, we used 16S rDNA sequencing technology and PICRUSt predicted functions to probe the characteristics of soil bacterial community diversity, structure, and function and influencing factors in a Pinus taiwanensis forest along an elevational gradient in the subtropical Wuyi Mountains. The results showed that: (1) Soil bacterial community diversity at 0-10 and 10-20 cm depth showed a nonlinear change along the elevational gradient. The community structure was significantly different between higher elevations (1800, 2000 m) and lower elevations (1200, 1400, 1600 m). (2) Predicted functions analysis showed six classes of level Ⅰ metabolic pathways, including 46 level Ⅱ metabolic pathways (showing rich functions), and predicted functional genes with high abundance exhibited significant differences along the elevational gradient. The relative abundances of carbohydrate metabolism, energy metabolism, metabolism of cofactors and vitamins, translation, folding, sorting, and degradation demonstrated an increasing trend with elevation. However, amino acid metabolism, xenobiotics biodegradation and metabolism, membrane transport, signal transduction, cell motility, cell growth and death, antimicrobial drug resistance, and environmental adaptation showed a decreasing trend. (3) There was a significant correlation between the relative abundance of genes involved in the level Ⅱ metabolic pathway of bacteria and relative abundance of Proteobacteria, Actinobacteria and Chloroflexi at different elevations. The differences of the predicted functional gene composition varied with bacterial community structure, which indicates that structure and function of bacterial community may be closely related. (4) Soil temperature and pH were the key factors affecting bacterial community structure and predicting functional genes in 0-10 cm layer, while pH and dissolved organic carbon were the key influencing factors in 10-20 cm layer. This study reveals the characteristics and driving factors behind the diversity, structure, and predicted functions of soil bacterial communities in a P. taiwanensis forest along an elevational gradient of Wuyi Mountains. Our findings provide a theoretical basis for further understanding the responses of soil bacterial communities to environmental changes, and the change of soil function in subtropical mountain forest ecosystems.

Key words: elevational gradient, soil bacteria, 16S rDNA, community structure, predicted function.