Relationships between soil microbial biomass determined by chloroform fumigation–extraction, substrate-induced respiration, and phospholipid fatty acid analysis

The soil microbial biomass (SMB) is responsible for many of the cycles and transformations of nutrients in soils. Three methods of measuring and describing this pool in soil are: (1) chloroform fumigation–extraction (CFE), (2) substrate-induced respiration, and (3) total extractable phospholipid fatty acids (PLFA). This study was conducted to seek a relationship between microbial PLFA and measures of SMB. Microbial PLFA was best predicted by CFE (R2=0.77); 1 nmol of PLFA corresponded to a flush of 2.4 μg C released by fumigation. This conversion factor will be useful in discussions of microbial populations and diversity and allow comparisons to literature in which only CFE is used to describe the size of the microbial biomass.