Relationship between dsDNA, chloroform labile C and ergosterol in soils of different organic matter contents and pH

We evaluated the relationship between dsDNA and microbial biomass C estimated by chloroform fumigation in eight soils from the Ultuna long-term experiment (37% clay, 41% silt and 22% sand). These soils have received different organic amendments and fertilisers, every other year since 1956, which have resulted in different soil C contents and pH. Chloroform-labile C and dsDNA concentrations ranged from 50 to 208 μg and from 24 to 95 μg g−1 of soil, respectively. Soil concentrations of dsDNA and chloroform-labile C were highly correlated (r=0.96). The ratios of ergosterol to chloroform-labile C and ergosterol to dsDNA varied between the soils, indicating differences in the fungal-to-total biomass ratio. Despite differences in microbial community composition, the concentration of dsDNA was generally proportional to the concentration of chloroform-labile C and the two appeared to be equivalent measures of soil microbial biomass.