Decomposition Characteristics of Coniferous Litter under Different Site Conditions in a Larix principis-rupprechtii Plantation | 不同立地条件下华北落叶松叶凋落物的分解特性

صينى. 采用凋落袋法,研究2种立地条件下不同林分密度华北落叶松人工林叶凋落物基质质量、分解速率的差异。结果表明：海拔与坡度是造成2种立地（地位级Ⅲ,Ⅳ）差异的主要因子,华北落叶松叶凋落物季节失质量率均表现出双峰曲线,且在秋季失质量率最高。2种立地条件下,叶凋落物半衰期分别为2.57,2.67年,完全分解分别需要11.09,11.24年。叶凋落物年平均失质量率、分解速率及初始无机养分含量均表现出立地Ⅲ高于立地Ⅳ。与立地Ⅳ相比,在立地Ⅲ下,C/N均值、木质素含量均值更有利于凋落物分解。经t检验分析,2种立地条件下叶凋落物初始无机养分含量之间并无显著差异性,而有机养分中木质素含量、有机碳含量之间差异显著（P〈0.05）。相关分析表明：凋落物分解速率与全碳、C/N、凋落物层厚度呈极显著负相关,相关系数分别为-0.735,-0.569,-0.758。叶凋落物质量指标表明：在立地Ⅲ条件下,林分密度为1675株・hm-2最为有利于凋落物分解;在立地Ⅳ条件下,则以林分密度1300株・hm-2最为有利于叶凋落物分解。

إنجليزي. The litter bag method was used to investigate the differences in dynamic weight loss rate,leaf litter decomposition rate and substrate quality of a Larix principis-rupprechtii plantation under different mountain site conditions in Beijing.The results showed that elevation and slope were two main factors in determining the site difference（Site class Ⅲ,Ⅳ）.There were two peaks for leaf weight loss rate under two site conditions during the one-year observation.T0.5 in Ⅲ and Ⅳ was 2.57 and 2.67 years,and t0.95 was 11.09 and 11.24 years,respectively.The average annual weight loss rate,the decomposition rate and initial inorganic nutrient content in Ⅲ were higher than in Ⅳ.Compared with Ⅳ,the average C/N value and lignin content in Ⅲ were more benefit to the decomposition of coniferous litter.The initial inorganic nutrient content of litter was not significantly different between two site conditions,while the initial content of C and lignin existed significant（P0.05） difference.Correlation analysis showed that there were significantly negative correlations between litter decomposition rate and total carbon,C/N ratio and litter layer thickness,and the correlation coefficients were-0.735,-0.569 and-0.758,respectively.Substrate quality indexes indicated that the forest density of 1 675 tree・hm-2 was most favorable to litter decomposition in Ⅲsite condition,while the density in 1 300 tree・hm-2 was the most beneficial to decomposition of coniferous litter in the Ⅳ site condition.