Decomposition of Leaf Litter in Pinus yunnanensis Forest and Evergreen Broad-Leaved Forest in Central Yunnan

The decomposition and its nutrient dynamics of leaf litters of Pinus yunnanensis, Cyclobanopsis glaucoides and Castanopsis orthacantha in pine forest stand and evergreen broad-leaved forest stand in central Yunnan had been investigated by using the litterbag method in a duration of 868 days. It was found that the decomposition rates of both broad-leaved leaf litters are greater than that of pine needles. There are obvious differences between pine forest stand and evergreen broad-leaved forest stand in decomposed mass loss of leaf litters of three species. The decomposition coefficients were 0 55～0 6 1a -1 for three leaf litters in evergreen broad-leaved forest, and in pine forest they were 0 50～0 53 a -1 . The removal rates of nutrient elements in litter change with the quality of leaf litter and decomposing site. During decomposition process the N, Al, Fe and Zn release of three leaf litters in both forest stands showed increase in the first period in content, and thereafter showed decrease over rest of this trial. P and Ca in decomposing leaf litters had also immobilization in evergreen broad-leaved forest stand. Mg and K exhibited a relatively rapid initial loss in the light of concentration and content, thereafter followed a steady decrease. The removal rates of nutrients in decomposing pine needles were lower than that of the other two broadleaf litters. The time and range of most elements immobilization of leaf litters in evergreen broad-leaved forest stand were cut down, and the decomposition speed of leaf litter increased, which indicates evergreen broad-leaved forest stand was beneficial to the decomposition of leaf litter and nutrients cycling in comparison with pine forest stand.