Despite Strong Temporal Responses, Soil Microbial Communities in Afforested Land Are Less Susceptible to Temporal Variability Than That in Farmland.

Afforestation have altered the plant diversity of ecological systems, with land use changes simultaneously enhancing the functional attributes such as resistance. However, how the below-ground microbial diversity following afforestation respond to temporal variability has received less attention. To illustrate the linkage of plant-soil- microbe following afforestation, and the effect of temporal variability on the soil bacterial community, we chose a farmland and three afforested lands, namely Robinia pseudoacacia L, Caragana korshinskii Kom, and abandoned land, which have been arable for the past 40 years. The study analyzed the changes in plant characteristics, soil characteristics and soil microbial communities in four periods via quantitative PCR and Illumina sequencing of the 16S rRNA genes. Both plant characteristics (plant diversity, above/belowground biomass, spatial heterogeneity index of herbaceous plants) and soil properties (soil water content, clay, organic carbon, total nitrogen, dissolved organic carbon/nitrogen, microbial biomass carbon/nitrogen, saccharase, urease and alkaline phosphatase) were synchronously increased after returning farmland to forest and were also influenced by temporal variability, but soil temperature and pH showed opposite trend. These indicated that the soil conditions have been improved after afforestation. Additionally, the diversities of soil bacterial communities, including alpha diversity (Shannon index, H) and beta diversity (Principle coordinates analysis, Bray–Curtis dissimilarity), were significantly affected by temporal variability and increased by afforestation. In combination with both plant and soil characters, higher plant diversity and soil nutrients presented higher bacterial diversity, which were less influenced by temporal variability that lower bacterial diversity in farmland, suggesting that afforestation strongly affect the above- and below-ground biomass and the spatial heterogeneity, thereby causing considerable increases in soil properties and associated soil microbial community, raising awareness regarding sustainable management of afforested plant.