English yew ( Taxus baccata ) is one of the few gymnospermous species present in the Hyrcanian forests, and it is listed as a rare and endangered species prone to extinction in Iran. This study aims to determine the ecological capability of Taxus baccata in the Hyrcanian region by identifying the diversity of plant communities dominated by this species, and to compare their floristic composition with the Taxus communities of southern Europe (Sicily, Corsica, Sardinia). We collected 408 relevés in the central and eastern part of the Hyrcanian forests. The classification of plant communities was performed using TWINSPAN. Phi-coefficient index, constancy ratio, and the ratio of average cover were used to determine diagnostic species in each vegetation unit. The expert system language of the JUICE program was applied to create formal definitions for syntaxa. The relationship between species and environmental factors were investigated with DCA. The environmental differences among the syntaxa were also tested with one-way ANOVA. Sums of constancy and average species cover of the diagnostic species of classes according to the EuroVegChecklist were computed. We distinguished five associations within three alliances. Of these, two associations and one alliance are new for science. Annual precipitation, elevation and annual temperature which are affected by elevational as well as longitudinal gradients were found to be important factors affecting the diversity of Hyrcanian Taxus communities. The constancy sum of diagnostic species was the highest for the class Carpino-Fagetea sylvaticae in all Hyrcanian and European units except for one Taxus community in Sardinia. We conclude that the Hyrcanian and southern European Taxus communities are similar in their floristically and ecological properties. Yew communities in the central Hyrcanian forests are associated with humid temperate diagnostic species, while semi-humid temperate plants are frequent in the eastern Hyrcanian forests, similar to the yew communities in southern Europe.

中文翻译：

---

希尔卡尼亚森林（伊朗北部）中以红豆杉为主的森林群落（共）分类及其与南欧的比较

英国红豆杉（Taxus baccata）是Hyrcanian森林中为数不多的裸子植物之一，在伊朗被列为濒临灭绝的稀有物种。本研究旨在通过识别以该物种为主的植物群落的多样性来确定 Hyrcanian 地区红豆杉的生态能力，并将其植物群落与南欧（西西里岛、科西嘉岛、撒丁岛）的红豆杉群落进行比较。我们在希尔卡尼亚森林的中部和东部收集了 408 个相关信息。使用 TWINSPAN 对植物群落进行分类。Phi 系数、恒定比和平均盖度比用于确定每个植被单元中的诊断物种。JUICE 程序的专家系统语言被应用于创建语法的正式定义。DCA研究了物种与环境因素之间的关系。语法之间的环境差异也用单向方差分析测试。根据 EuroVegChecklist 计算类别的诊断物种的恒定性和平均物种覆盖率的总和。我们区分了三个联盟中的五个协会。其中，两个协会和一个联盟对科学来说是新的。发现受海拔和纵向梯度影响的年降水量、海拔和年温度是影响希尔卡尼亚红豆杉群落多样性的重要因素。除了撒丁岛的一个红豆杉群落外，所有希尔卡尼亚和欧洲单位中 Carpino-Fagetea sylvaticae 类的诊断物种的恒常性总和是最高的。我们得出结论，Hyrcanian 和南欧红豆杉群落在植物区系和生态特性上相似。希尔卡尼亚中部森林中的红豆杉群落与潮湿的温带诊断物种有关，而半湿润的温带植物在希尔卡尼亚东部森林中很常见，类似于南欧的红豆杉群落。