Does conversion from natural forest to plantation affect fungal and bacterial biodiversity, community structure, and co-occurrence networks in the organic horizon and mineral soil?

Abstract

Tree species influence the chemical properties of the organic horizon and mineral soil. Microbial communities, including fungi and bacteria, which are the main drivers of nutrient cycles in forest soils, may be affected by tree species via litter chemical properties and root exudation. Therefore, conversion from natural forest to plantation could affect the microbial communities. Here, we aimed to reveal the effects of conversion from natural forest to coniferous plantation on soil microbial community structure, biodiversity, and co-occurrence networks, as well as soil chemical properties. For this purpose, we investigated chemical and microbial properties of the organic horizon and mineral topsoil (0–10 cm depth) in three forest types (a natural forest dominated by broad-leaved deciduous trees, and two types of plantations). Forest type had significant effects on chemical properties, including the C/N ratio, pH, and dissolved inorganic N of the organic horizon, while it had no significant effect on the chemical properties of topsoil, except for microbial biomass N and C. Microbial community structures in both the organic horizon and topsoil differed significantly among forest types and with changes in soil properties such as pH and C/N ratio. Microbial diversity indices did not significantly differ among forest types in either layer, while the microbial co-occurrence networks in the mineral soil of the natural forest were more complex and robust than the networks of plantations. Therefore, our results showed that conversion from natural forest to coniferous plantation could affect soil chemical properties and microbial community structure in the organic horizon, and the microbial co-occurrence network in the mineral topsoil; these impacts may vary according to the planted tree species.