Impacts of deforestation and forest regeneration on soil bacterial communities associated with phosphorus transformation processes in the Brazilian Amazon region

Abstract

Land-use change has negative impacts on the biodiversity of plants and animals. However, we lack studies and/or information about the impacts of land-use change on the biodiversity of soil microorganisms, especially those involved in the phosphorus (P) transformation processes. This represents a great concern since some microbial groups are extremely important to different P transformation processes and regulate P availability in tropical and subtropical regions. In our study, we used shotgun DNA-metagenomic sequencing and P fractionation analysis to assess the effects of forest-to-pasture conversion on the dynamics of soil bacterial groups involved in the P transformation processes and their potential functions. Additionally, we assessed if the dynamics of these specific soil bacterial groups were recovered after pasture abandonment and with secondary forest establishment. Our results demonstrated that the land-use change altered the total amount of P and its fractions in the soils. The bacterial community structure was affected by changes in soil chemical properties, mainly by changes in the aluminum, total P, and labile P contents. The bacterial groups involved in the P transformation processes and their potential functions were also affected by changes in land use. The pasture soil harbored a distinct bacterial community when compared to the primary and secondary forest sites. In general, forest-to-pasture conversion increased bacterial groups involved in the P mineralization, including Firmicutes, Cyanobacteria, and Gemmatimonadetes. Conversely, we observed an increase of Proteobacteria members (e.g., Bradyrhizobiaceae and Beijerinckiaceae) and genes related to P solubilization and mineralization after pasture abandonment and with the secondary forest re-establishment. Our multi-analytical approach suggests that forest-to-pasture conversion has negative impacts on the biodiversity of bacterial groups involved in the P transformation processes and their potential functions, while the secondary forest re-establishment can stimulate resilience. Taken together, our results indicated that the bacterial groups involved in the P transformation and their potential functions can be gradually recovered and reach intermediate and/or even similar levels to those observed in undisturbed forest sites. This brings new insights and helps to improve our knowledge about the impacts of anthropogenic actions on the soil microbiome in the Amazon region.