Afforestation with Pinus sylvestris var. mongolica remodelled soil bacterial community and potential metabolic function in the Horqin Desert

Soil bacteria have been widely investigated and their roles in terrestrial ecosystems are relatively well understood. The soil bacterial community and potential function are controlled by vegetation and bacteria are factors indicating changes in soil microenvironment. However, there is a knowledge gap regarding microbial influence and their use to predict the change in metabolic function after afforestation in desert ecosystem. Pinus sylvestris var. mongolica is the most important evergreen species in desertified northern China. Therefore, we used the 16S rRNA high-throughput sequencing and PICRUSt platform to identify the soil bacterial community and potential metabolic function across stand ages (HQh: half-mature forest, HQn: nearly-mature forest, HQm: mature forest) and control (CK, natural grassland) in the Horqin Desert. Soil characteristics were determined to clarify edaphic driving factors and reveal the effect of afforestation on bacteria. The results indicated that (1) The dominant soil bacterial community category was stable but potential metabolic function changed across stand ages. The dominant phyla and genera were Proteobacteria and Acidobacteria and Sphingomonas, RB41, respectively; the metabolic functions changed from carbohydrate to amino acid metabolism. (2) P. sylvestris plantations significantly increased soil bacterial diversity (P < 0.05). Catalase was significantly correlated with soil bacterial diversity (P < 0.05). (3) The driving factor of the bacterial community was Urease in the CK plot. Afforestation changed the soil organic matter (SOM) in HQh and HQn, but urease was restored in HQm. The dominant soil characteristics that affected potential metabolic function were soil porosity (SP) and total nitrogen (TN) in the CK plot, total phosphorous (TP) and SOM in HQh, catalase activity in HQn, and urease in HQm. The changes in dominant soil characteristics forecasted that afforestation broke traditional desert grassland ecological balance, established a new forest ecological balance by changing soil environment, and indicated that the potential metabolic pattern changed from resource acquisition to resource utilization. This may herald the creation of new ecosystems in deserts. Our results provide strong microbial evidence that evaluated the significance of afforestation in arid regions