Changes in soil microbial communities are linked to metal elements in a subtropical forest

As one of the primary divers of microbial changes, soil metals have been extensively studied in agroecosystems. Soil microbial processes in forests are crucial for maintaining plant biodiversity; however, the contributions of soil metals toward such processes remain poorly understood. In the present study, 1287 soil samples collected from a 20 ha forest plot were analyzed. The results showed that the levels of seven metal elements (Al, Ca, Cu, Fe, Mg, Mn, and Zn) were better indicators of changes in microbial communities than soil properties (organic carbon, pH, and water content), macronutrients (AK, AP, NH₄⁺-N, NO₃⁻-N, TN, and TP), and topographic (elevation, convexity, and slope) or spatial factors. Furthermore, Mn was found to be the most influential metal element regarding microbial functions. The initial responses of biomarkers to metal elements influenced microbial functions. The responses of microbial α-diversity and community structure to these elements, as well as the correlations between soil metals and microbial functions, were affected by both the C:N ratio and soil pH. Although it may still be too early to assign causality, our study is one of the first to link soil metals to changes in forest microbial communities. These findings advance our capacity to predict belowground microbial processes by establishing the importance of metals in forest soils, providing a solid theoretical basis for forest biodiversity conservation under the context of global climate change.