Carbon assimilation and microbial activity in soil

Abstract In order to characterise the term microbial „activity”︁ three different microbial populations belonging to a luvisol (I), a phaeozem (II) and a rendzina (III) were used for studying kinetic parameters such as substrate affinity, growth rate, yield and turnover time and the metabolic quotient of basal respiration. Glucose was used as a carbon source. Specific growth rate values (μ) varied between 0.0037 and 0.015 h −1 depending on soil type and glucose concentration and were far below the potential μ max . The calculated turnover time was 3–11 days, respectively. The yield coefficient was in the range between 0.37 and 0.53. The maximal uptake rate of glucose–C of soil population (II) was 0.041 g C g −1 biomass‐C h −1 . The determined affinity constant (K m ) was 57 μg C g −1 soil. The affinity to glucose was higher for the glucose‐mediated CO 2 evolution with K m values of 15.2 and 17.5 than for the glucose uptake system itself. The observed qCO 2 values of the basal respiration at temperature increments from 0 to 45° C were almost identical for the soils (I) and (II). The calulated Q 10 lay in the range between 1.4 and 2.0.