林木直径大小多样性量化测度指数的比较研究

Study on Diversity Indices of Tree Diameter Size

[目的]为了客观恰当地量化表达林分水平上的林木直径大小多样性。[方法]采用6块定位样地数据,对比分析基于直径分布的Simpson(D_N)、Shannon(H_N)及单木断面积Gini系数(GC),基于直径大小分化度的Simpson(DT)、Shannon(HT)及其均值(T-)这6种林木直径大小多样性量化测度指数,筛选出符合逻辑排序且具有较好辨别能力的直径大小多样性量化测度指数。[结果]6块样地的林木直径大小多样性逻辑排序为吉林胡桃楸针阔混交林经营样地>吉林胡桃楸针阔混交林对照样地>甘肃锐齿栎阔叶混交林经营样地>甘肃锐齿栎阔叶混交林对照样地>北京油松落叶松人工混交林样地>北京侧柏人工纯林;林木直径大小多样性为天然林高于人工林,更为成熟的吉林老龄林样地高于甘肃中龄林样地,经过至少5年结构化经营的样地高于对照样地,人工混交林样地高于人工纯林样地。基于直径分布的DN、HN和GC测度的6块样地林木直径大小多样性排序结果与逻辑排序不一致;基于直径大小分化度的D_T、H_T和珔T测度的各林分林木直径大小多样性排序与逻辑排序一致。[结论]基于直径分布的D_N、H_N和GC量化测度指数不能恰当地表达林木直径大小多样性。基于直径大小分化度的D_T、H_T和珔T量化测度指数能恰当表达林木直径大小多样性;相对D_T和H_T,珔T是一个连续型变量的测度指数,而且能从林分整体水平上量化林木间的大小分化程度,易于解释其生物学意义。因此,认为珔T是恰当表达及区分各林分林木直径大小多样性的最优量化测度指数。

[Objective]To evaluate the tree size diversity of natural and artificial forest.[Method]The data of 6 sample plots were compared and used to estimate the 6 size diversity indices,including size diversity indices that based on diameter distribution of Simpson （DN）,Shannon （HN）and individual tree basal area of Gini coefficient （GC）,and the size diversity indices that based on differentiation of diameter distribution of Simpson （DT）,Shan-non（HT）and its mean value （T）.[Result]The results showed that the size diversity logical ranking of the 6 plots was successively the contrastive plot of Juglans mandshurica mixed broadleaf-conifer forest in Jilin〉the structure-based forest managed plot of J.mandshurica mixed broadleaf-conifer forest in Jilin 〉the structure-based forest managed plot of Quercus aliena var.acutiserrata broadleaved mixed forest in Gansu 〉the contrastive plot of Q.ali-ena var.acutiserrata broadleaved mixed forest in Gansu 〉the plot of Pinus tabulaeformis and Larix gmelinii mixed plantation〉the plot of Platycladus orientalis mixed plantation.The size diversity of natural forest was higher than that of the artificial forest,the more matured stand of old-growth forests in Jilin was higher than half-matured forest in Gansu,the stand been applied structure-based forest management for at least 5 years was higher than the contras-tiveplot,themixedartificialstandwashigherthanthepureartificialstand.[Conclusion] Theorderingresultsof methods GC,HN and DN showed inconformity to the logical ranking,stating that the methods based on diameter dis-tribution could not properly express the differences of size diversity.The ordering results of methods T,DT and HT showed conformity to the logical ranking,stating that the methods based on diameter differentiation distribution could properly express the differences of diameter diversity among the 6 plots.It was better for T to discriminate the differ-ences among 6 plots than DT and HT,due to its ability to estimate continuous variable,reflecting the differential de-gree between the target trees and the nearest neighboring trees,and that prone to explain its biological meaning. Therefore,it is considered that the T珔as the best method to express the diameter size diversity.