Taxa-specific changes in soil microbial community composition induced by pyrogenic carbon amendments

The effects of pyrogenic carbon on the microbial diversity of forest soils were examined by comparing two soil types, fire-impacted and non-impacted, that were incubated with laboratory-generated biochars. Molecular and culture-dependent analyses of the biochar-treated forest soils revealed shifts in the relative abundance and diversity of key taxa upon the addition of biochars, which were dependent on biochar and soil type. Specifically, there was an overall loss of microbial diversity in all soils treated with oak and grass-derived biochar as detected by automated ribosomal intergenic spacer analysis. Although the overall diversity decreased upon biochar amendments, there were increases in specific taxa during biochar-amended incubation. DNA sequencing of these taxa revealed an increase in the relative abundance of bacteria within the phyla Actinobacteria and Gemmatimonadetes in biochar-treated soils. Together, these results reveal a pronounced impact of pyrogenic carbon on soil microbial community composition and an enrichment of key taxa within the parent soil microbial community.