北京雾灵山自然保护区核桃楸群落的优势种种间联结分析

为了解北京山区核桃楸种群的自然生长状况，于2007年8月对分布于北京雾灵山自然保护区核桃楸群落及其自然生境采用典型抽样的方法进行了研究。共设置面积为20 m×20 m 的样地6块，并把每块样地划分为16个5 m×5 m的小样方，在小样方尺度上，调查了核桃楸种群及其群落中占有一定优势地位的紫椴、黄檗、北京丁香和鹅耳枥的分布情况；用2×2列联表和χ2检验研究了核桃楸与紫椴、黄檗等在主林层、演替层和更新层的种内、种间联结性。结果表明:①主林层中核桃楸与演替层中的核桃楸呈显著正联结；与更新层中的北京丁香呈极显著负联结，且联结系数值较大；与其他物种在不同演替层间正联结种对数小于负联结。②演替层中核桃楸与不同林层间其他物种的正联结种对数大于负联结。 

Interspecific association analysis in dominant species of Juglans mandshurica community in Wuling Mountain Nature Reserve of Beijing

In order to understand the natural growth status of Juglans mandshurica community in Beijing mountain area，J. mandshurica community and its natural habitat in Wuling Mountain Nature Reserve of Beijing were studied using a typical sampling method in August 2007. Six sample plots were used and each plot (20m×20 m) was divided into 16 quadrates (5 m×5 m). The dominant species of J. mandshurica community (Tilia amurensis, Phellodendron amurense, Syringa pekinensis and Carpinus turczaninowii) were investigated. Based on 2×2 contingency tables and chi square test，the authors analyzed the spatial associations of intra and interspecies among T. amurensis, P. amurense, S. pekinensis and C. turczaninowii in the canopy，subcanopy and understory layers. The results show that Juglans mandshurica population in the canopy layer was positively associated with that in the subcanopy layer and negatively associated with S. pekinensis population in the understory layer. The association coefficients were large. Compared with the number of species pairs with positive associations，fewer negative associations were found between J. mandshurica population and others in three vertical layers，while the number of species pairs with the positive associations was greater than that with negative association between J. mandshurica population in the subcanopy and others in three vertical layers.