山西霍山白桦种群不同龄级立木的点格局分析

以山西霍山地区的先锋树种之一白桦( Betula platyphylla)为研究对象,在霍山七里峪林场典型地段设置一个50 m×50 m的样方,应用点格局分析方法对其不同龄级(Ⅰ级、Ⅱ级、Ⅲ级和Ⅳ级)个体的分布格局及相互关系进行了研究.结果表明:(1)白桦种群不同龄级的个体间密度也不相同,中间龄级Ⅱ级(7 cm＜ DBH≤14 cm)和Ⅲ级(14 cm ＜DBH≤21 cm)的密度较大,幼龄和老龄个体密度小,年龄结构为衰退型；(2)除Ⅰ级(DBH≤7 cm)外,其余3个龄级集群分布特征比较明显,且随着龄级的增加,集群特征有更明显的趋势；(3)除Ⅰ级和Ⅱ级、Ⅱ级和Ⅲ级、Ⅱ级和Ⅳ级(DBH ＞21 cm)之外,其余龄级间基本都是小尺度下负关联,并随尺度的增大关联性逐渐变得不显著.

Spatial Pattern Analysis of Individuals in Different Age-classes of Betula platyphylla in Huoshan Mountain of Shanxi Province

Betula platyphylla is a pioneer plant and is distributed intensively in Huoshan mountain.One 50 m×50 m quadrat was established in Qiliyu from which we recorded the DBH of each individual and the spatial points of all individuals were mapped.The data were analyzed by point pattern analysis.All individuals were divided into four DBH classes： DBH Ⅰ（DBH≤7 cm）;DBH Ⅱ（7 cm〈DBH≤14 cm）;DBH Ⅲ（14 cm〈DBH≤21 cm）;DBH Ⅳ（DBH〉21 cm）.The results of this study showed：（1） The densities of four age-classes varied in the order： age-class Ⅱ〉age-class Ⅲ〉age-class Ⅰ〉age-class Ⅳ.The middle age-classes Ⅱ and Ⅲ had many more individuals than age-classes Ⅰ and Ⅳ,which indicated that the population was currently in decline.（2） The individuals of all age-classes focused on clumping distribution in space,except the age-class Ⅰ.The feature of clumping distribution became more significant with increasing age.（3） The relationships between individuals in different age-classes were significantly correlated with each other on a small scale,but became non-significant with increasing scale,except for age-classes Ⅰ and Ⅱ,age-classes Ⅱ and Ⅲ,and age-classes Ⅱ and Ⅳ.