Microbial biomass growth, following incorporation of biochars produced at 350 °C or 700 °C, in a silty-clay loam soil of high and low pH

► Biochar colonization more pronounced with biochar produced at 350 °C than 700 °C ► 20% of microbial biomass 13C derived from biochar350 at 90 d in pH 8 and 4 soils. ► Less than 2% of biomass 13C was derived from biochar700 in the high pH soil. ► Correlation of 13CO2 and biomass 13C shows biochar mineralization is biological. ► Biomass changes after biochar addition confirmed by Scanning Electron Microscopy.