Abstract:Litter decomposition is an important process of ecosystem nutrient cycling, which plays an important role in biogeochemical cycling. Global change is an important factor affecting litter decomposition, but there are many uncertainties in its impact on ecosystem nutrient cycling. Studies on the response and feedback of litter decomposition of desert steppe to the increased nitrogen deposition and precipitation change will provide the scientific basis for revealing these uncertainties and protecting the structure and function of grassland ecosystem. In this study, taking S. breviflora desert steppe in Siziwang Banner, Inner Mongolia as the research object, two kinds of plant litter, the dominant species S. breviflora and C. songorica, were selected to carry out a 4-year decomposition experiment, to explore the litter decomposition characteristics and nutrient release patterns of the two kinds of plants. The experiment used split-pot design, with precipitation as the whole-plot factor and N as the split-pot factor. Precipitation treatments include addition 30% (W), removal 30% (R), and ambient precipitation(C). Nitrogen was added at 0 (N0), 30 (N30), 50 (N50) and 100 (N100) kg hm^-2 a^-1. The results show that:(1) Increased precipitation and nitrogen deposition promoted litter decomposition in the desert steppe. Furthermore, the precipitation effects were different between the two kinds of litter, while the effect of nitrogen deposition does not depend on species; (2) Nitrogen deposition shortened the litter decomposition duration by 5.12%-14.82%, and the interaction between precipitation enhancement and nitrogen deposition shortened the litter decomposition duration by 3.69%-28.75%; (3) Precipitation was always beneficial to the release of carbon, cellulose and lignin from litter, but nitrogen deposition had no significant effect on it in the later stage of litter decomposition, and the late stage of litter decomposition is mainly controlled by the decomposition rate of lignin. In conclusion, the main factor affecting the decomposition of litter in the desert steppe is precipitation, followed by nitrogen, and the two factors have a synergistic effect on decomposition of litter.