Abstract: To study the characteristics of litter decomposition of the dominant tree species of mountain forests in arid areas under different precipitation conditions, a field simulation experiment was performed with three precipitation treatments of ZP(zero precipitation), CK(natural precipitation), and DP(double precipitation). The impact of precipitation intensity on the decomposition of litter(leaves and branches) and the fine roots of Picea schrenkiana was investigated. Compared with decomposition rates of leaf, branch and fine root under CK treatment, those of under ZP treatment were 24.79%,2.54% and 23.09% lower, whereas, those of under DP treatment were 7.04%, 0.68% and 10.70% higher, respectively. ZP treatment significantly inhibited the decomposition of leaf litters and fine roots(P<0.05) and weakly inhibited the decomposition of branch litters(P>0.05). DP treatment only significantly promoted the decomposition of fine roots(P<0.05). For the CK and DP treatments, the monthly average decomposition rates of leaf litters and fine roots and branch litters showed single-peak curves, respectively, whereas the monthly average decomposition rates of litters and fine roots were relatively stable for ZP treatment. The remaining rates of the lignin and cellulose from different organs showed that ZP>CK>DP. With the different precipitation treatments, the release patterns of N were different, whereas the release patterns of C were essentially the same. By correlation analysis, the monthly decomposition rate of litter was not significantly correlated with soil temperature at depths in 0 10 cm(P>0.05) but showed a significant positive linear correlation with the soil water content(P<0.05). Our findings highlight that future climatic change effects should fully consider the organ-dependent differences of litter and root decomposition in arid mountain forests.

Key words: precipitation intensity, litter, decomposition, nutrient release, Picea schrenkiana var. tianshanica, arid mountain forest