MEASUREMENT OF MICROBIAL BIOMASS IN ARCTIC TUNDRA SOILS USING FUMIGATION EXTRACTION AND SUBSTRATE-INDUCED RESPIRATION PROCEDURES

The microbial biomass of seven arctic tundra soils was measured using both the chloroform fumigation-extraction procedure (biomass-C and -N) and the substrate-induced respiration method (biomass-C only) to test the suitability of these two methods for organic and mineral arctic soils. Results indicate that in general the two methods gave consistent microbial biomass-C measurements. Microbial biomass-C, estimated by the fumigation-extraction procedure (using K(ec) = 0.35) was highly correlated (r = 0.831, P < 0.001) with the microbial biomass-C values measured by the substrate-induced respiration technique across all soil types. Microbial biomass-N of the seven arctic soils measured by the fumigation-extraction procedure showed a higher linear correlation with the biomass-C values produced by the substrate-induced respiration procedure (r = 0.88) than those produced by the fumigation-extraction procedure (r = 0.69). This result seems to suggest that the fumigation-extraction procedure works better for microbial biomass-N measurements than for biomass-C in these arctic soil conditions. The fumigation-extraction and substrate-induced respiration methods, developed to study mostly temperate agricultural soils, can be successfully applied to arctic tundra soils.