Kingdom-Asymmetric Responses of Soil Bacterial and Fungal Communities to Forest Types Along an Elevational Gradient in a Subtropical Mountain Forest

Forest types vary in root exudation, litter quality, microclimate, and soil properties, but their impact on microbial community assembly, especially when mixed with elevation, is unclear. Using high-throughput sequencing, phylogenetic null-model analysis, and co-occurrence network inference, we profiled topsoil microbiomes in four forest types, including coniferous, deciduous, mixed and plantation, in a subtropical mountain. Soil bacterial alpha diversity varied significantly by forest type, being lower in coniferous stands, while fungal diversity showed limited variation. Soil bacterial communities were more distinct across forest types than fungal ones. Co-occurrence network analysis revealed plantation-specific bacterial over-connectivity and deciduous-specific fungal fragmentation. Bacterial assembly varied by forest type, with heterogeneous selection in deciduous forests, homogenizing dispersal in plantations, and mixed processes in coniferous and mixed forests. Fungal assembly was marked by homogenizing selection and dispersal limitation. Soil bacterial structure was linked to phosphorus, moisture, and pH, while fungal differentiation was tied to C:N ratios and spatial factors. Because the results derive from a single sampling and forest type was confounded with elevation, controlled studies are needed to separate vegetation effects from climate and soil influences and to confirm the potential linkages among taxa.