The Control of Nitrogen Turn-Over in Forest Litter

Abstract

A semi-empirical model for describing the nitrogen dynamics of decomposing forest litter in a medium-long time perspective is presented. Derived results indicate the strong regulating influence of decomposition rate and initial nitrogen concentration of the litter on its retention and release of N. An increased decomposition rate tends to reduce the rate of N release per unit of carbon mineralized. This makes the ,critical C/N ratio of a litter, below which a net N mineralization takes place, lower the higher the decomposition rate. For a litter of low initial N concentration a faster decomposition generally also means a greater immobilized amount of N but a shortened immobilization phase. The peak of mineralized N is more marked and comes earlier the lower the C/N ratio and the higher the decomposition rate. Furthermore, in all litter types the C/N ratio becomes narrower as decomposition proceeds, but the change levels out earlier and on a lower level the higher the decomposition rate. The possible role of these features as regulating factors for N distribution in soil and in secondary succession of forest ecosystems is discussed.