Abstract: The effect of precipitation variation on chemistry of Quercus mongolica leaf litters was ex-amined by analyzing litters of Mongolia oak saplings under 4 precipitation gradients, and the decom-posing process of these leaf litters in Q. mongolica dominated forest was assessed using litter bag method. The results showed that under less precipitation, the litter had a higher decomposition rate , and its N, P and K mineralized quickly. The initial concentrations of N, P, and K increased, while that of lignin decreased significantly. With increasing precipitation, the mineralization rates of N, P and K in litter decreased. Its initial N concentration decreased, while the relative content of lignin increased. The mass loss patterns of four type litters fitted exponential model, and the decom-position rate could be well predicted by their lignin/N ratio. The decomposition rate of the litters with higher lignin and lower N was best related to their N concentration, while that of the litters with lower lignin and higher N was strongly correlated with their lignin concentration. It was proved that precipitation had a significant effect on the litter substrate quality of Q. mongolica, and thus, changed the decomposition process of the litter indirectly.

Key words: Winter wheat, Summer maize, Nitrogen fertilizer, Soil nitrogen mineralization, First order dynamic model