湖南针栎混交林直径分布及演替动向
Diameter Distribution and Succession Tendency of Coniferous Oak Mixed Forest in Hunan Province

为揭示湖南省针栎混交林林分结构，了解林分树种更替过程以及指导针栎混交林抚育间伐奠定理论基础，以湖南省5块针栎混交林样地为研究对象，采用偏度和峰度描述栎类林分的直径分布特征，利用正态分布、Weibull分布、Gamma分布以及Logistic分布函数分别对针栎全林分和栎类林分的直径分布进行拟合，同时以林分株数变化动态为依据，分析针栎混交林的演替动向。结果表明：1）5个样地的偏度系数＞0，说明栎类直径分布曲线为左偏，林分中中小径阶的栎类林木所占比重较大。除5号样地在2004年的峰度＜0外，其余样地的峰度＞0，表明栎类直径分布相对比较集中，呈现尖峰态；2）Weibull分布函数和Gamma分布函数更适于拟合针栎全林分和栎类林分的直径分布规律，但在拟合栎类林分的直径分布规律时效果更优；3）针栎混交林分中的栎类比例随着生长时间的延长逐渐增加，而针叶树逐步退化，针栎混交林逐步演替为阔栎混交林。
The objectives of this study were to provide the theoretical basis for revealing the forest structure,understanding the replacement process of the tree species and guiding the improvement cutting.Based on the five conifer and oak sample plots in Hunan Province,the skewness and kurtosis were used to describe the diameter distribution characteristics of oak forest,functions,including the normal distribution,Weibull distribution,Gamma distribution,and Logistic distribution were adopted to fit the diameter distribution of conifer-oak forest and pure oak forest.Meanwhile,the succession tendency of conifer and oak forest was analyzed based on the change of plant number.The results showed that 1) the coefficient of skewness of the 5 sample plots were above 0，indicating that the distribution curve of the diameter of oak was left deviated，and the proportion of medium and small forest trees was large.Except for sample plot No.5,the values of kurtosis of other sample plots were above 0,indicating that the diameter distribution of oak was relatively concentrated and presented a peak state.2) The Weibull distribution function and Gamma distribution function were more suitable for fitting the diameter distribution rule of the whole forest and pure oak forest,and the result was better when fitting the diameter distribution rule of the pure oak forest.3) The proportion of oak species in coniferous and oak forest increased gradually with growing time,and coniferous forest gradually replaced by quercus species forest