Aims Litter decomposition is a fundamental process of ecosystem functioning, which is largely dependent on biodiversity of the ecosystems. We explored the effects of species diversity and genetic diversity of litter on its decomposition rate. Methods We used laboratory microcosms to determine whether species diversity and genetic diversity of leaf litter or their interaction affect its decomposition. We set 8 treatments which contain 1, 2, 4 diversity levels of four broad-leaf species (Alniphyllum fortunei、Idesia polycarpa、Cinnamomum camphora、Daphniphyllum oldhamii) and genetic diversity. All litter samples were taken back to the laboratory, and oven-dried. Total 246 containers were stored in the dark at 25℃ for 12 weeks. Important findings The effect of litter species diversity on litter decomposition was largely dependent on species composition of the litter mixture in terms of species identity. Overall, the decomposition rate increases linearly with the seed family richness when the species identity was neglected. However, no interactive effect of species diversity and genetic diversity on mass loss was detected. Litter decomposition rate was found to be unrelated to the initial C, while negatively correlated with the initial total N and N:P ratio. However, the regression curve of litter decomposition rate against total P and C:N ratio displayed quadratic parabola opening upward and downward respectively. This study demonstrated the importance of species and/or genetic diversity and composition of litter per se during its decomposition, and also stressed the effects of litter chemistry. Further studies should be done in longer term to ascertain how such effects work and how they change during decomposition process, especially in response to various composition and diversity of surrounding plants. 2016-11-03 15:52:45 UTC prep SP04e The role of genetic diversity and phenotypic plasticity in the context of the species diversity – ecosystem functioning relationship Yuewei Tong tyw8704123@163.com Zhengweng Wang zhengweng_wang@mail.cn Yuewei Tong tyw8704123@163.com Journal of Plant Ecology 2016-11-03 accepted