Influence of proximity to the Qinghai-Tibet highway and railway on variations of soil heavy metal concentrations and bacterial community diversity on the Tibetan Plateau

An understanding of soil microbial communities is crucial in roadside soil environmental assessments. The 16 S rRNA sequencing of a stressed microbial community in soil adjacent to the Qinghai-Tibet Highway(QTH) revealed that the accumulation of heavy metals(over about 10 years) has affected the diversity of bacterial abundance and microbial community structure. The proximity of a sampling site to the QTH/Qinghai-Tibet Railway(QTR), which is effectively a measure of the density of human engineering, was the dominant factor influencing bacterial community diversity. The diversity of bacterial communities shows that 16 S rRNA gene abundance decreased in relation to proximity to the QTH and QTR in both alpine wetland and meadow areas. The dominant phyla across all samples were Actinobacteria and Proteobacteria.The concentration of Cr and Cd in the soil were positively correlated with proximity to the QTH and QTR(MC/WC sampling sites), and Ni, Co, and V were positively correlated with proximity to the QTH and QTR(MA/WA sampling sites).The results presented in this study provide an insight into the relationships among heavy metals and soil microbial communities, and have important implications for assessing and predicting the impacts of human-induced activities from the QTH and QTR in such an extreme and fragile environment.