A mono-component model of carbon mineralization with a dynamic rate constant

The difficulties in using complicated models of carbon mineralization and t he poor performance of simple ones call for new models that are simple in u se and robust in performance. We have developed a model for the mineralizat ion of carbon from experimental data in which the organic matter is treated as a single component. The logarithm of the average relative mineralizatio n rate, K, or rate constant, of a substrate considered as a whole was found to be linearly related to the logarithm of time, t, provided prevailing so il conditions remained unchanged. The equation is: logK=logR - Slogt, or K= R t(-s), in which R (dimension t(S-1)) represents K at t=1, and S (dimensio nless, 1 greater than or equal to S greater than or equal to 0) is a measur e of the rate at which K decreases over time, also called the speed of 'age ing' of the substrate. The quantity of the remaining substrate, Y-t, is cal culated by Y-t = Y-0 exp(-Rt(1-S)), where Y-0 is the initial quantity of th e substrate. The actual relative mineralization rate, k, at time t is propo rtional to K, according to k=(1-S)K. The model was tested against an assemb ly of 136 sets of data collected from trials conducted in 14 countries all over the world. They cover materials ranging from glucose, cellulose and pl ant residues, to farmyard manure, peat and soil organic matter. The results lead to the conclusion that the model describes well the dynamics of organ ic matter in soil over time varying from months to tens of years, provided major environmental conditions remain unchanged. It can easily be applied i n practice and is attractive because of its modest input requirements.