Nitrogen and phosphorus release from decomposing litter in relation to the disappearance of lignin

Concentrations of nitrogen, phosphorus, and acid insoluble substances were followed in decomposing forest foliage litters in some different forest biomes and in a laboratory study. In all cases, the concentration of these substances increased linearly with litter mass loss. In contrast, absolute amounts of these materials in the litter began decreasing at some point during decay, usually following a period of absolute increase (i.e., immobilization of nutrients or humification for acid insoluble substances). The point during decomposition at which a net release (net disappearance) of a substance began (point for maximum amount), was estimated using the linear relations between concentrations of the substance and accumulated litter mass loss. In addition, the concentrations of acid insoluble substances at maximum absolute amounts of nitrogen and phosphorus were estimated. The results indicate that the points in decay at which a net release of nitrogen and phosphorus began were linearly related to one another and to the onset of acid insoluble substance disappearance. In all litters studied, net release of nitrogen and phosphorus began after a net release of the recalcitrant acid insoluble substance fraction had begun. The relationship between the onset of acid insoluble substance loss and nitrogen and phosphorus release differed between deciduous and coniferous foliage litters. Key words: decomposition, litter, nitrogen, phosphorus, lignin, nitrogen release, phosphorus release.