不同稀有种处理对双向指示种分析分类结果影响的比较

为探讨不同稀有种处理对TWINSPAN分类结果的影响，以北京小龙门林场华北落叶松林调查数据为例，采用2×2列联表比较了剔除频度＜5%、盖度＜5%的稀有种前后TWINSPAN分类结果的异同，同时结合引入的DBI重点对比了最佳分类等级的吻合性。结果表明：(1)在相同的分类终止原则下，剔除稀有种前后的最大分类结果分别分为12、11个群落类型；(2)基于结合系数r，剔除稀有种前后TWINSPAN在低分类等级的结果差异较大，随着分类等级的增加，二者的吻合度增大，表明稀有种对低分类等级的结果影响较为明显；(3)引入的DBI适用于确定TWINSPAN分类的最佳分类等级，尽管剔除稀有种前后的最佳分类等级不同，但分类结果的吻合度较高。因此，在TWINSPAN分类应用中，建议引入DBI指数辅助确定最佳分类等级，同时取低分类等级结果时必须做删除稀有种处理。

Effects of Different Rare Species Treatments on Two-way Indicator Species Analysis

For comparing the impact of different treatment methods on TWINSPAN, we studied two different methods of eliminating rare species and untreated with the plant communities and environmental survey data of Xiaolongmen Forest Farm. Match coefficient and Davies-Bouldin index(DBI) were taken to compare the result of two different TWINSPAN classification for ensuring the best classification division. Before and after eliminating accidental species, the TWINSPAN classification result among the same classification principles of termination was, respectively, divided into 12 and 11 associations. With the combination coefficient r, the low grade of TWINSPAN classification results of before and after eliminating rare species were not consistent, with the increase of classification level, the ground adhesion coefficient was higher and higher, and the rare species greatly influenced the result of the low grade of TWINSPAN classification. DBI index as the division criterion was introduced to obtain the optimum TWINSPAN classification results. Although the best classification of grade was different before and after eliminate rare species, but with higher classification results of alignment the degree of agreement between two ones was higher. Therefore, in the application of TWINSPAN classification, when introducing DBI index to determine the best classification, the low classification results of rare species should be deleted.