Purpose Litter decomposition is a fundamental process of biogeochemical cycles. Mixing litter of different species can induce non-additive effect (NAE) on decompostion processes. A better understanding of the factors influencing the direction and magnitude of NAE is important for quantification of ecosystem carbon and nutrient cycling.Methods Litter mixing effects on leaf litterdecomposition were examined using two parallel experiments (each with leaf leaf litter of four tree species combained into four diversity levels) conducted in Chinese temperate forestsfor 2 years.Results A significant diversity effect in both experiments demonstrated NAEs of litter mixing on the mass remaining. Separating the diversity effect into species richness and composition was statistically significant in both experiments whereas as effect of species richness was only detected in Experiment 2. In both experiments, the NAE on decomposition changed with incubation time and showed a declining trend during decompostion process. However, a sligh difference of the NAE in the two experiments was observed in our study. Decompoition in the litter mixtures differed from the predictions based on single species, and the presence/absence of polar, pne and oak in the litter mixture significantly influenced the direction and magnitude of the NAE. Presence of coniferous species litter significantly reduced decomposition rates even within the same species richness level. The coefficient of variation of remaining litter mass was lower in the treatements with higher number of litter species.Conclutions Our findings showing of changes in the direction and magnitude of NAE with decomposition time and litter species composition indicate that tree species composition and decomposition duration should be considered in predicting biodiversity effect on biogeochemical cycling in temperature forests.