Mass loss and nutrient release during litter decomposition drive biogeochemical cycling in terrestrial ecosystems. However, the relationship between the litter decomposition process and the decomposition stage, precipitation and litter quality has rarely been addressed, precluding our understanding of how litter decomposition regulates nutrient cycling in various ecosystems and their responses to climate change. In this study, we measured mass loss as well as carbon and nutrient releases during the decomposition of 16 types of leaf litter under three precipitation treatments over 12 months in a common garden experiment (i.e., using standardized soil and climatic conditions). Sixteen types of leaves were divided into 3 functional groups (evergreen, deciduous, herbaceous). The objectives were to understand the effects of decomposition stages and precipitation regimes on litter decomposition and to examine the relationship between this effect and chemical properties. The mass loss and release of nitrogen and potassium were significantly higher in the 6-12 month stage of decomposition (high temperature and humidity) than in the 0-6 month stage. Phosphorus was relatively enriched in evergreen leaves after 6 months of decomposition. The rates of mass loss and nutrient release were significantly greater in herbaceous than in deciduous and evergreen leaves. Increasing precipitation from 400 to 800 mm accelerated mass loss and potassium release but decreased phosphorus release in the 0-6 month stage of decomposition. These results highlighted the contribution to and complexity of litter chemical properties in litter decomposition.

 After 12 months of field tests, a large number of samples have been tested in the laboratory to obtain test data.  All the statistical analyses were carried out using SPSS software (Version 19.0, IBM, USA). Principal component regression analysis was performed using the R software package v.3.3.2 (R Core Team 2018).

In this study, we selected leaves from 16 species that are widely distributed in Shaanxi Province and vary markedly in their leaf chemical properties.  The 16 species belonged to 6 deciduous trees, 4 evergreen trees, and 6 herbaceous.we defined the early and late stages of decomposition as the 0-6 and 6-12 month decomposition, respectively. Tthe designed precipitation treatments were 400, 600 and 800 mm per year. The litter before decomposition was prepared for the analysis of the concentrations of C, N, P, K, lignin and cellulose. The samples after 6 and 12 months of decomposition were prepared for the analysis of the C, N, P and K concentrations. There are missing values in the data.