中文摘要：

以大兴安岭林区不同发育阶段兴安落叶松人工林和天然次生林为研究对象，采用野外调查和定量分析相结合的方法，对林地土壤有机质、土壤腐殖质组成、土壤酸度指标及其主要养分含量的变化进行测定和分析。利用主成分分析的方法，以各主成分特征贡献率为权重，加权计算各林地土壤肥力综合指标值。结果表明：随着林龄的增长，不同发育阶段落叶松人工林土壤酸度总体呈现升高的趋势，土壤有酸化的迹象；全磷和速效钾呈现降低的趋势；有机质、水解氮、胡敏酸和胡敏素含量在近熟林略有升高，但总体呈现降低的趋势。土壤肥力评价结果为：天然林〉幼龄林〉近熟林〉中龄林〉成熟林，即随着林龄的增长，土壤肥力迅速下降，其主要原因是林地凋落物分解缓慢。因此，建议通过适度提高林地抚育强度，调整群落结构，增加林地光照，诱导天然阔叶树种进入，形成针阔混交林的调控措施，调节落叶松人工纯林凋落物分解与积累的矛盾，以维持地力平衡和提高林地生产力。

英文摘要：

The research object was based on larch （Larix gmelinii） plantations at different development stages and natural secondary forest in the forest area of Daxinganling Mountains. Using the combined methods of field investigation and quantitative analysis, the changes of soil organic matter, the composition of soil humus, soil acidity indices and their chief nutrition content were determined and analyzed. By the methods of principal component analysis, the contribution rate of each principal component character was used as weight; Integrated fertility index in every forest type was computed by the weighted calculation The results were shown as follows： with the increase of the stand age, the soil acidity presented increasing tendency in larch plantations of different development stages, the soil began to acidify. The content of total phosphorus and available kalium presented decreasing tendency, and the content of organic matter, hydrolysable nitrogen, humic acid and humin increased slightly in near mature stand, but totally decreased. Comprehensive evaluation of soil fertility showed the results： natural forest 〉 young stand 〉 near mature stand 〉 half-mature stand 〉 mature forest, namely, with the stand ages increasing, soil fertility began to decrease rapidly because of the slow litter decomposition. It is proposed that the intensity of partial cutting should be increased properly in order to adjust community structure, increasing forestland light, inducing the entrance of natural broad-leaved trees into larch plantations, forming coniferous and broad-leaved mixed forests, regulating the contradiction of larch plantations litter between decomposition and accumulation, keeping the soil fertility balance and raising forest productivity.