Soil respiration curves, measured under constant conditions, change after an initial phase to a relative steady course. Now there is an adjustment of an ecological equilibrium in the activity of soil microbes. This state of equilibrium is characterized by a linear course of the log CO2 = f(log t)-curves and is named "Grundatmung" (basic respiration). If this equilibrium ist disturbed by application of primary organic substances or the availability of slowly decomposable organic matter, then microbial growth-phases appear dominating as first-order reactions in the form of increased CO2-delivery. However, in the further course this process changes over again to the state of "Grundatmung".--This linearity of the log CO2 = f(log t)-curves is explained by the existence of a whole series of superimposed first-order reactions, synthetisizing secondary biomasses in the substrate.--This linearity permits a temporary extrapolation of the CO2-release of soils and is important for the quantification of the soil habitat (zoning) mineralisation.