THEORETICAL-ANALYSIS OF CARBON AND NUTRIENT INTERACTIONS IN SOILS UNDER ENERGY-LIMITED CONDITIONS

The cycles of S and P in soil have received only limited attention from a theoretical or modeling point of view, relative to those of C and N. In this study, the interactions between the cycles of C, N, P, and S in decomposing litters and soils have been analyzed using a theory based on changes in substrate quality during decomposition. The C cycle requires information about microbial efficiency and growth rate as functions of substrate quality, with initial litter quality as a parameter distinguishing different materials. Nitrogen, P, and S are given similar descriptions and the parameters differentiating them are the concentrations of the elements in microbial populations and fresh litter. The theoretical predictions are compared with empirical data on C, N, P, and S behavior in a number of different conditions covering both steady states of soils and dynamics in incubation experiments in laboratories. The agreement between theoretical and empirical results indicate that the cycles of N, P, and S basically follow similar rules.