Effect of temperature on soil microbial biomass and its metabolic quotient in situ under different tillage systems

摘要

Variations in the microbial biomass and the in situ metabolic quotient (qCO2) due to climatic conditions were determined in a typical soil from the Argentine Rolling Pampa. Microbial C was evaluated by fumigation-incubation andqCO2was calculated using soil respiration in the field. An inverse relationship between microbial C and soil temperature was fitted to a model (r2=0.90,P=0.01). No significant association with the soil water content was detected because the soil was generally near field capacity and thus water availability did not limited microbial growth and activity. Values ofqCO2increased (r2=0.89,P=0.01) as the result of metabolic activatìon, likely induced by a higher maintenance energy requirement at high temperatures. The highest values ofqCO2were obtained when microbial C was the lowest, which was attributed to self consumption of microbial C in the presence of high temperatures. Consequently, microbial C was generally higher (P=0.05) in winter than in summer. Therefore, when microbial C is used as an index of soil biological activity, the influence of temperature should be taken into account