基于分层的半天然马尾松阔叶混交林直径分布

Diameter Distribution of Semi-natural Mixed Forest of Pinus massoniana and Broadleaved Trees Based on Stratification

[目的]研究半天然马尾松阔叶混交林各林层(包括全林和各亚层)的直径分布,揭示其直径分布特征,为其可持续经营提供基础依据。[方法]基于10块半天然马尾松阔叶混交林样地,采用最大受光面法划分林层,利用Shapiro-Wilk检验对各样地各林层直径分布进行正态性检验,利用峰度和偏度系数描述直径分布图形特征,采用三参数Weibull分布和Meyer负指数函数拟合各样地各林层直径分布,用卡方检验法检验拟合效果,并选择效果较好的函数拟合各样地直径分布图,分析林分直径分布特征。[结果]有5块样地的第Ⅰ亚层服从正态分布,但所有样地全林和第Ⅱ亚层的直径分布均呈反J形且不服从正态分布。所有样地全林和各亚层的偏度系数均为正值,有7块样地的全林峰度系数小于0,大多数样地全林的偏度系数及峰度系数绝对值介于第Ⅰ亚层和第Ⅱ亚层之间。Weibull分布函数对全林和第Ⅰ亚层的拟合效果较好,全林、第Ⅰ亚层、第Ⅱ亚层的卡方检验通过率分别为80%、100%、70%;Meyer负指数函数对第Ⅱ亚层的拟合效果较好,而对全林和第Ⅰ亚层的适应性较差,特别是第Ⅰ亚层的通过率仅为10%,但第Ⅱ亚层的通过率达100%。[结论]半天然马尾松阔叶混交林各林层的直径分布差异显著,第Ⅰ亚层倾向于正态分布,全林和第Ⅱ亚层的直径分布均呈反J形且都不服从正态分布;从第Ⅱ亚层到第Ⅰ亚层直径分布表现出由负指数分布向正态分布过渡的趋势。所有样地各林层的直径分布曲线均为右偏,大多数样地的全林直径分布曲线呈低峰态。Weibull分布函数对全林和第Ⅰ亚层的拟合效果较好,而Meyer负指数函数则适用于拟合第Ⅱ亚层直径分布。

[Objective]The diameter distribution of each storey(including the whole stand and sublayers) of seminatural mixed forest of Pinus massoniana and broadleaved trees was studied to reveal the diameter distribution characteristics of the stand and provide data for their sustainable management. [Method]Based on 10 semi-natural mixed forests plots, the maximum light-receiving plane method was used to divide storey, and the Shapiro-Wilk test was used to measure the normality of the diameter distribution of each plot and storey;the skewness and kurtosis coefficients were used to describe the graphic characteristics of the diameter distribution. The diameter distributions of each plot and storey were fitted by three-parameter Weibull distribution and the Meyer negative exponential function, and the chi-square test was used to test the fitting effect, then the function with better fitting effects was selected to fit the distribution chart of each plot, and analyzed the distribution characteristics of the stand. [Result]There were five plots whose sublayer Ⅰ obeyed normal distribution, but for all sample plots, the diameter distribution of all the whole stand and the sublayer Ⅱ followed an inversed J shape were not obeying normal distribution. The skewness coefficient of all the whole stand and sublayers were positive value, the kurtosis coefficient of the whole stand of 7 plots were less than 0, and for most plots the skewness coefficient and the absolute value of the kurtosis coefficient of the whole stand were between that values of the sublayer Ⅰ and the sublayer Ⅱ. The Weibull distribution function has a good fitting effect on the whole stand and the sublayer Ⅰ. The pass rates of the chi-square test of the whole stand, the sublayer Ⅰ and the sublayer Ⅱ were 80%, 100%, and 70%, respectively. Meyer negative exponential function could fit the sublayer Ⅱ better, while the adaptability to the whole stand and the sublayer Ⅰ were poor, especially the pass rate of the sublayer Ⅰ was only 10%, but the pass rate of the sublayer Ⅱ reached 100%. [Conclusion]There are significant differences in the diameter distribution of the whole stand and each sublayer of the semi-natural mixed forest of P. massoniana and broadleaved trees, the diameter distribution of sublayer Ⅰ tends to be normal distribution while the whole stand and the sublayer Ⅱ are inverse J shaped and not obeying normal distribution. The diameter distribution from sublayer Ⅱ to sublayer Ⅰ shows a transition trend from negative exponential distribution to normal distribution. For all sample plots, the diameter distribution curves of each storey are right-skewed, and the curves of the whole stand of most sample plots are platykurtic. The Weibull distribution function has a good fitting effect on the whole stand and the sublayer Ⅰ, while the Meyer negative exponential function is suitable for fitting diameter distribution of sublayer Ⅱ.