Grazing promoted plant litter decomposition and nutrient release: A meta-analysis

Abstract

Grazing considerably affects ecosystem nutrient cycling and element stoichiometry at the regional and global levels according to synthesized studies. However, the effects of grazing, especially its intensity, on the plant litter decomposition stage of key processes in biogeochemical cycles are not clearly understood. Here, a meta-analysis of 65 published papers was undertaken to examine the responses of eight variables associated with litter decomposition to grazing or grazing intensity. We also explored whether experimental and environmental factors altered the effects of grazing on litter decomposition. Our results indicated that grazing significantly promoted litter decomposition when all the data was averaged, and that the magnitude of its effects on litter decomposition became weaker as grazing intensity increased. Grazing did not affect mixed root litter decomposition, but increased single root litter decomposition, and light grazing had a stronger positive effect. Specifically, grazing significantly accelerated litter C and P release, and significantly increased single N release by single above-ground litter, but not root or mixed aboveground litter. In addition, environmental factors (e.g., elevation, and mean annual precipitation) and experimental factors (e.g., experiment duration and litterbag size) affected the litter decomposition responses to grazing. These results suggest that the effects of grazing on litter decomposition and nutrient release depend on grazing intensity, litter type, and plant organs. Grazing alters terrestrial plant litter decomposition and grazing intensity plays an important role in regulating the magnitude of the effect during litter decomposition and nutrient cycling.