Comparison of bacterial and fungal diversity and network connectivity in karst and non-karst forests in southwest China.

Microbial communities contribute to sustaining the function of terrestrial ecosystems and are influenced by soil type and climate gradients. The effects of karst and non-karst soils on bacterial and fungal profiles for seven climate gradients were assessed to better understand bacterial and fungal diversity and community composition in response to soil type with changes in soil physicochemical properties under different temperatures and precipitations. Bacterial and fungal abundance, diversity, and community composition differed between karst and non-karst forests. Bacterial and fungal richness, Shannon index, and bacterial abundance in karst forests were higher than non-karst forests, but the fungal abundance was lower. Mean annual temperature was negatively correlated with bacterial diversity in the karst forest and fungal abundance in karst and non-karst forests. The community composition of bacteria and fungi differed among these two soil types. The karst forest had greater connectivity among bacterial and fungal communities than non-karst forests. The bacterial members of Acidobacteria, Proteobacteria, Actinobacteria, and fungal groups of Ascomycota and Basidiomycota were mainly connected with other taxa in the network, implying that taxa were associated with highly functional potential. The relative abundance of Actinobacteria and Ascomycota was higher in karst than in non-karst forests. Proteobacteria and Basidiomycota showed the opposite results. A random forest and multiple regression tree analyses revealed that soil properties, specifically pH, calcium, and total nitrogen, were the main factors influencing the variation in bacterial and fungal profiles between karst and non-karst forests. This study provides novel evidence that the abundant microbial taxa were kinless hubs in co-occurrence patterns. Controlling complex networks of species interactions may contribute to improving soil nutrient processes rather than microbial diversity, enhancing our understanding of developing sustainable recovery strategies in fragile ecosystems.