长白山云冷杉林主要树种空间分布及其关联性

Spatial distribution patterns and associations of main tree species in spruce-fir forest in Changbai Mountains,northeastern China

为揭示长白山云冷杉林物种共存的维持机制，基于Ripley’sK的双相关函数g（r），分析了5．2hm。云冷杉林中鱼鳞云杉和臭冷杉的种群结构、空间分布格局及其种间空间关联性。结果显示：样地中鱼鳞云杉与臭冷杉共8730株，占样地全部个体数的68．1％，胸高断面积之和占样地全部个体胸高断面积的51．9％，在样地中占据绝对优势地位。2个树种的径级结构均呈反“J”型分布。空间格局分析显示：小径级的臭冷杉和鱼鳞云杉均呈聚集分布，尤其是在小尺度上更加明显；而随着径级增大，则呈随机分布，聚集强度也随尺度的增大而降低。臭冷杉的大树和小树在0—50m尺度上呈负相关，显示这2组个体存在非常激烈的种内竞争。而不同径级的鱼鳞云杉之间在小尺度上表现为负相关或无明显相关性，说明鱼鳞云杉的种内竞争相对较弱。小径级的臭冷杉与所有径级的鱼鳞云杉，小径级的鱼鳞云杉与所有径级的臭冷杉均呈正相关关系，表明2个树种均适宜在对方林冠下生存。臭冷杉和鱼鳞云杉的中径级和大径级的个体，两两之间呈负相关或无显著相关性；表明随着径级的增大，臭冷杉与鱼鳞云杉之间存在强烈的种内和种间竞争。2个树种的种群分布格局主要受到种子扩散限制和负密度效应的影响，而相似的耐荫性使得2个树种可以在该森林群落中长期共存。

To reveal the mechanisms for species coexistence of spruce-fir forest communities in Changbai Mountains, northeastern China, the population structure, spatial distribution patterns and spatial associations of Abies nephrolepis and Picea jezoensis were analyzed by g（r） function based on Ripley＇ s K- function in a 5.2 hm2 spruce-fir forest community plot. The results showed that the two species had a total of 8 730 individuals, and accounting for 68.1% of the total individuals. The basal areas of two species accounted for 51.9% , and may suggest dominant status of two species in the plot. The DBH-class structures of the two species exhibited inverse ＂J＂ type distributions each. Spatial pattern analysis showed that the small-sized individuals of A. nephrolepis and P. jezoensis displayed an aggregated distribution, especially at small scales. The individuals were randomly distributed as the increase of DBH-class, and the aggregated intensity became lower with the increase of scales. The A. nephrolepis showed negative correlations between small-sized individuals and large-sized individuals at 0-50 m scales, and couldsuggest intense intraspecific competition between the two groups. The P. jezoensis species exhibited negative correlations or no significant correlations among different DBH-classes at small scales, indicating that the intraspecific competition was relatively weak. It showed positively correlations between the small- sized A. nephrolepis and all DBH-classes P. jezoensis, as well as between small-sized P. jezoensis and all DBH-classes A. nephrolepis; it may indicate those two species could survive below the canopy of each other. The middle-sized and large-sized individuals of A. nephrolepis and P. jezoensis were negatively correlated and not significantly correlated from one to another, and suggesting the existence of intense intraspecies and interspecies competitions between the two species as the increase of DBH-class. The spatial distribution patterns of the two species were mainly affected by seed dispersal limitations and the negative density-dependent effect, while similar biological characteristics （shade tolerance） made them coexist in this forest community.