Leaching, accumulation and release of nitrogen in decomposing forest litter

Abstract

The release through leaching is dependent on the litter type, and appears to be of a magnitude of significant importance to the system. One important factor which determines whether accumulation will take place or not is the nitrogen concentration in the litter. lt appears that the nitrogen level for accumulation varies with the system, ranging from about 0.3 (C/N ca. 170) to 1.4% (C/N ca. 26). When an accumulation of nitrogen takes place, the rate in a given system is proportional to the decomposition rate, and the accumulation continues until the critical nitrogen Ievel is reached. During accumulation a part of the nitrogen is bound up in the fraction of lignin and humification products. Release of nitrogen starts either at the beginning of the decomposition process or after an accumulation phase. The release after an accumulation starts when the nitrogen level has reached a critical nitrogen level, which is higher for litters/systems with a high decomposition rate than those with low decomposition rates. Once release of nitrogen has started, it appears to be in proportion to the weight -loss rate. Finally, the importance of these phases in terms of nitrogen recycling to plants is discussed .