Abstract: By using field litter bag technique, this paper studied the decomposition rate and nutrient release of the leaf litters from Pinus tabulaeformis, P. armandii, Larix principis-rupprechtii, and Quercus aliena var. acuteserrata in Qingling Huoditang forest area. After two years decomposition, the remaining percentage of the leaf litters was 35.6%-58.6%, and ranked as P. tabulaeformis > P. armandii > L. principis-rupprechtii > Q. aliena var. acuteserrata. Except that P. tabulaeformis and P. armandii had no significant difference in their leaf litters remaining percentage, there existed significant differences in the remaining percentage among the test tree species. During the two-year experiment, the leaf litters decomposed fastest during the period from April to September, and kept a stable decomposition rate in other months. Compared the second year, the mass loss rate of the leaf litters in the first year was higher, and showed obvious seasonal and stage-wise difference. The estimation of the required time to decompose 50% and 95% of the leaf litters by the Olson model showed that there was a prominent discrepancy among the tree species. The required time to decompose 95% of leaf litter was the shortest (5.43 years) for Q. aliena var. acuteserrata, and the longest (9.87 years) for P. tabulaeformis. The elements N and P in leaf litters appeared enrichment in  first year of decomposition, and started to release after the  enrichment peak reached; while the C presented a decreasing trend. The differences in  decomposition rate and nutrient release rate among the tree species were mainly related to the initial quality and the nature of the leaf litters.

Key words: Beauveria bassiana, Emulsifiable conidia suspensions, Myzus persicae, Field trial, Aphid control