中文摘要：

在2009年5月到2010年10月。以小兴安岭地区3种林龄的天然白桦次生林（20a，36a，82a）为研究对象，采用网袋分解法研究不同林龄的白桦林凋落物分解过程中的残留量和养分动态变化。结果表明：不同林龄白桦林在分解过程分为两个阶段：快速分解阶段（0～150d）和缓慢分解阶段（150—540d）。凋落物残留量随时间呈指数变化趋势。年分解常数k值在0．584—0．657，凋落物分解50％和95％所用的时间分别为1．06～1．19a和4．56～5．13a。3种林龄白桦天然次生林分解速率从大到小依次为82a〉36a〉20a。在凋落物分解过程中，C和K元素浓度不断释放，而N和P元素浓度先上升后下降，最终N元素为富集，P元素为释放模式。

英文摘要：

Taking three ages Betula platyphflla secondary forests （20a, 36a, 82a） in Xiaoxing＇an Mountains, China as test objects, this paper studied their remaining rates and nutrient dynamics from May 2009 to November 2010 by using decomposition bag method. The results of two year decomposition showed that the different ages of B. platyphylla secondary forests had a fast decomposing stage （0 - 150 d） and a slow decomposing stage （ 150 - 540 d）. For all test litters, their remaining rate had an exponential relationship with time. The annual decomposition constant （k） ranged from 0.584 to 0. 657, and the times for decomposing 50% and 95% were 1.06 - 1.19 years and 4.56 - 5.13 years, respectively. The decreasing order of litter decomposition rate of these three ages of the B. platyphylla secondary forests was 82a 〉 36a 〉 20a. During decomposition, the elements carbon and potassium in litter released continuously, and the concentrations of nitrogen and phosphorus increased first and then decreased, N concentration of three different ages forests was in enriched mode and P concentration was in released mode in the later period.