[Altitudinal Distribution Pattern of Soil Bacterial Communities in Different Soil Layers and Driving Factors in the Forests of Mountain Zhela， Xizang].

To investigate the distribution pattern and main driving factors of soil bacterial community structure and diversity along the altitudinal gradient in different soil layers of alpine forests， this study examined and sampled two soil depths， 0-20 cm and 20-40 cm， along the altitudinal gradient of 3 400-4 300 m in the Zhela Mountains of southeastern Xizang. Redundancy analysis （RDA）， random forest analysis （RF）， Spearman correlation analysis， and Mantel's test were used to investigate the distribution pattern and its main driving factors. The study produced several important results： ① Acidobacteriota and Proteobacteria， Acidobacteriae， and norank__ f__norank__o_Subgroup__2 dominated the alpine forest ecosystem. Their relative abundance accounted for a relatively high percentage， and no significant changes were found in the dominant groups of bacterial communities at different elevations. ② The four alpha diversity indices of soil bacteria were generally higher in the 0-20 cm soil layer than in the 20-40 cm soil layer and were highest at 4000 m above sea level. Soil bacterial beta diversity was significantly distributed at different elevation gradients. ③ RDA， RF， and Mantel's test indicated that soil nitrogen， TK， EC， and pH were the main driving factors affecting the variation of soil bacteria by altitudinal distribution pattern. Soil SOC， NH₄⁺-N， and TK were the main driving factors affecting the alpha diversity of soil bacterial communities by altitudinal distribution pattern. The sensitivity of soil bacteria to soil physicochemical factors was higher in the 0-20 cm soil layer than in the 20-40 cm soil layer. ④Neutral community model （NCM） analysis revealed that the assembly mechanism of soil bacterial communities in the two soil layers was mainly driven by deterministic processes. The results showed that there was variability in the structure and diversity of soil bacterial communities under different altitudinal gradients and soil horizons in the Zhela Mountains and that soil nitrogen， TK， EC， pH， and Temp play important roles in shaping the mechanism of bacterial community assembly and are important drivers of their distribution along the altitudinal gradient. The results of this study provide an important basis for understanding the pattern of soil bacterial community structure and diversity along the altitudinal distribution in different soil layers.