四川黄龙沟内分布着十分丰富的兰科植物(19属30余种)，并且部分种类在沟内形成优势群落。目前尚不清楚在群落中这些兰科植物种之间作用关系。运用种间关联分析和相关分析对黄龙沟森林植被兰科植物群落中的24个优势种的种间关系进行了研究。两种分析方法得到的结果相近，表明黄龙沟优势兰科植物可以分为两组。一组包括无苞杓兰(Cypripedium bardolphianum)、黄花杓兰(C. flavum)、二叶红门兰(Orchis diantha)、广布红门兰(Orchis chusua)、少花虾脊兰(Calanthe delavayi)和西藏杓兰(C . tibeticum)，主要分布在光线充足但又具有一定遮荫条件的环境中；另一组包括筒距兰(Tipulari a szechuanica)、沼兰(Malaxis monophyllos)、珊瑚兰(Corallorhiza trifida)、小斑叶兰(Goodyera repens)、布袋兰(Calypso bulbosa)、小花舌唇兰(Platanthera minutiflora )和小叶对叶兰(Listera smithii)，它们主要分布于荫蔽的环境中。这些兰科植物在组内大多呈现显著的正相关关系，组间大多呈现显著的负相关关系，说明黄龙沟兰科植物在资源利用方式上可能产生了分化。
Aims The Huanglong Valley of Sichuan is rich in orchid species, with >30 species in 19 genera, and some orchids dominate the herbaceous layer. However, little is known about their interspecific relationships. Our aim was to investigate how the orchid species interact with each other and with other species.
Methods We sampled 6 621 m×1 m releves in the orchid communities in Huanglong Valley, selected 24 dominant species according to importance values and studied interspecific associations and correlations by usingχ2_tests and Spearman rank correlations.
Important findings Results of χ2_tests of species associations and Spearman rank correlations were consistent and indicated two groups of dominant species. One group, including Cypripedium bardolphianum,C. flavum, C. tibeticum, Orchis diantha, O. chusua and Calanthe delavayi, is mostly distributed where both light and shade are provided by tree overstories. The other group, including Tipularia szechuanica, Malaxis monophyllos, Corallorhiza trifida, Goodyera repens, Calypso bulbosa, Platanthera minutiflora and Listera smithii, is mostly distributed in shade. Non-orchid species, Arctous rube, Gentiana scabra, Pedicularis davidii , Elymus nutans and Pinguicula alpine,which are mostly distributed in open areas, are significantly positively correlated with orchid species of the first group , but mostly negatively correlated with the second group. In contrast, Clintonia udensis, Pedicularis humilisandCarex lehmanii, which are mostly distributed i n shaded environmental conditions, have reverse correlations with the two orchid groups. Polygonum macrophyllum, Pyrola callianthaand the orchid Oreorchis nana show no obvious correlations with either of the orchid groups. Our findings indicate that the interspecific interactions of orchid species of Huanglong Valley are complex and the orchid species may have differentiated with regard to the resource use. Reproductive facilitation may play an important role for orchid species diversity in this area.