Variations of soil metal content, soil enzyme activity and soil bacterial community in Rhododendron delavayi natural shrub forest at different elevations

Abstract Background Rhododendron delavayi is a natural shrub distributed at different elevations in the karst region of Bijie, China, and has an importance in prevention of land degradation in this region. The soil bacterial community structure of R. delavayi at three elevations (1448 m, 1643 m, 1821 m) was analyzed by high-throughput sequencing, and soil mineral elements and enzymes activities were determined. Results In this study, our results showed that the soil Fe, Mg, Cr, Ni, Cu and Zn content decreased with increase in elevations, the soil K content varied in a V-shape, while the soil Cd and Pb showed an inverted V-shape. In addition, the variation of soil urease and phosphatase activity also showed an inverted V-shape. Invertase activity increased while catalase activity decreased with elevation increase. The Shannon index of soil bacterial community initially increased and then decreased with elevation, and was highest at 1643 m. At 1821 m, Fe was positively correlated with Acidobacteria; Ca, Ni, Cu, Zn and Pb were positively correlated with Actinobacteria. Urease and phosphatase significantly affected the soil bacterial community, while elevation affected the diversity of bacterial community by affecting Fe and urease content. The results of Linear discriminant effect size (LEfSe) showed that there were different biomarkers at different elevations. The bacterial co-occurrence network analysis showed that the dominant bacterial communities at different elevations in Baili Rhododendron scenic spot had a complex structure. Acidobacteria, Actinobacteria and Proteobacteria were the most dominant phyla at 1448 m, 1643 m and 1821 m. Mantel test and correlation analysis showed that Fe and urease significantly affected bacterial OUT at 1448m. Moreover, Cr, Ni and catalase had a negative impact on TM7 at 1448m but there was no significant correlation between soil variables and bacteria communities on bacterial OUT at 1643m and 1821m. Conclusion Elevation significantly influenced structure of bacterial communities by affecting the content of soil mineral elements and the level of enzyme activity.