INFLUENCE OF TEMPERATURE ON CO2 EVOLUTION, MICROBIAL BIOMASS-C AND METABOLIC QUOTIENT DURING THE DECOMPOSITION OF 2 HUMIC FOREST HORIZONS

The decomposition of the litter layer and the humic mineral horizon from a beech forest site was studied at temperatures of 5, 12, and 22 degrees C for both substrates and additionally at 32 degrees C for beech litter. Weight losses, basal and substrate-induced CO2 production, and the extractable biomass C were monitored periodically during a 2-year incubation period. Weight losses and microbial activity were controlled by substrate quality and temperature. No significant differences were found between 5 and 12 degrees C in decomposition, biomass C, and the metabolic quotient in the humic mineral horizon. The decay of beech litter and the humic mineral horizon was highest at 22 degrees C but was faster in the litter material by a factor of 2.9 on average. In the glucose-amended samples, the relationship among the CO2-C fluxes was 1:1:2:3 at temperatures of 5, 12, 22, and 32 degrees C in the litter layer, and 1:2:2.4 at 5, 12, and 22 degrees C in the A horizon, respectively. The microbial activity in the humic mineral horizon was only 2-11% of that in the litter layer The level of biomass C remained constant over 1 year and no significant differences were obtained from the 12 and 22 degrees C treatments in the litter layer.