Intensification of agricultural practices on calcareous soils leads to drastic changes in biogeochemical processes due to modifications of CO 2 partial pressure in soil pores. For this reason, CO 2 evolution was measured in vitro from Typic Rendoll soils of the Champagne Crayeuse at four temperatures. Microbial biomass was also estimated by a plate‐count technique that had been calibrated by two independent methods: chloroform fumigation and bioluminescence. Carbon dioxide evolution curves fit an equation consisting of a zero‐ and first‐order reaction. The three parameters of this equation were interpreted as: (i) the amount of easily decomposable organic matter generated by the disturbance, (ii) the time constant for the disappearance of that disturbance, and (iii) the sustained respiration of the native microflora. This model implies that the rate of CO 2 evolution is maximum at the start of the incubation, while the observed maximum in bacterial biomass occurred about 5 d later. Comparison of the results presented here with data from the literature shows that there is an almost continuous spectrum of values for the amounts of easily decomposable organic matter generated by any disturbance, and that the time constant for its mineralization is of the order of a very few days. Therefore, the use of the double exponential model is superfluous unless the duration of the incubation experiments exceeds 100 d.
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Blet‐Charaudeau et al. (1990) studied this question.