Impact of native tree species introduction on soil nutrient and bacterial community in Eucalyptus plantations

The introduction of native tree species can enhance soil ecological functions and mitigate the decline in soil status triggered by the high-intensity monoculture of Eucalyptus plantations, but the specific impact is still unclear. In this study, differences in the structural and function for soil bacterial communities were investigated between evergreen broad-leaved secondary forests, Eucalyptus pure plantations, and mixed plantations of Eucalyptus with two native species in Guangxi: Manglietia glauca and Mytilaria laosensis , respectively. Additionally, soil physicochemical properties and enzyme activities were determined. The results showed that pH, soil sucrase and peroxidase activities, and bacterial alpha-diversity indices were significantly higher in Eucalyptus mixed plantations with M. glauca and M. laosensis , compared to Eucalyptus pure plantations. Bacterial biomarkers ( Burkholderiales, Bradyrhizobium, and Actinobacteria ) with nitrogen fixation and phosphate solubilization functions were enriched in Eucalyptus with M. glauca and M. laosensis . Redundancy analysis showed that pH, effective boron (AB), and soil moisture were the main soil environmental factors driving changes in the structure of the soil bacterial community. Thus, we concluded that mixed plantations of Eucalyptus with M. glauca or M. laosensis have positive effects on mitigating soil acidification, increasing soil enzymatic activity, and improving soil ecological functions, which provides useful information for the development of sustainable management of Eucalyptus plantations.