EFFECT OF SOIL CO2 CONCENTRATION ON MICROBIAL BIOMASS

The effect of increasing soil CO2 concentration was studied in six dif ferent soils. The soils were incubated in ambient air (0.05 vol.% CO2) or in air enriched with CO2 (up to 5.0 vol.% CO2). Carbon dioxide evo lution, microbial biomass, growth or death rate quotients and glucose decay rate were measured at 6, 12 and 24 h of CO2 exposure. The decrea se in soil respiration ranged from 7% to 78% and was followed by a dec rease in microbial biomass by 10-60% in most cases. High CO2 treatment s did not affect glucose decay rate but the portion of C-gluc minerali zed to CO2 was lowered and a larger portion of C-gluc remained in soil s. This carbon was not utilized by soil microorganisms.