Microbial community diversity and composition across a gradient of soil acidity in spruce-fir forests of the southern Appalachian Mountains

► We evaluated the impact of acid deposition on microbial diversity in high elevation forests in US. ► Strong acidophilic bacterial species were identified common to acid mine drainage and low pH sites. ► Actinobacteria, Acidobacteria, Proteobacteria, and Chloroflexi were dominant in the soils.