四川黄龙沟草本层植物种类组成与数量特征

Characteristics of Plant Species in Herb Community in Huanglong Valley,Sichuan

四川黄龙沟草本植物群落在所调查样方中(N=662)共出现维管植物124种,分属于37科91属,有54个中国特有种:其中兰科植物多达21属33种,中国特有种有12个,新种一个。如此众多的地生兰科植物聚集在面积不到1公里的沟内,而且部分兰科植物种类在沟内形成优势草本群落,这在中国地生兰的分布区域中是不多见的。大多数物种,包括兰科植物在内,出现的频率都较小,并且分布不均匀。黄龙沟兰科植物主要分布在两种生境中,即钙化滩流地和森林中。在这两种生境中微环境条件以及兰科植物的种类组成、数量特征和分布格局的差异都很大。钙化滩流地的兰科植物种类数目和每个样方中包含的兰科植物种类数目都比森林生境中的高。钙化滩流地中发现有30种兰科植物,最为常见的是无苞杓兰、黄花杓兰、西藏杓兰、广布小碟兰、二叶根茎兰和少花鹤顶兰。森林生境中有21种兰科植物分布,其中筒距兰和斑叶兰出现最多,光照强度可能对兰科植物的分布起到重要的决定作用。钙化滩流地中的溪流对建立和维持兰科植物生存所必须的稳定环境条件起到至关重要的作用,如果随意改变水流的方向或减少水流的流量,将给某些兰科植物带来灾难性的后果。

There are 124 understory species in the 662 sampled plots,belonging to 37 families and 91 genera,of which 54 are endemic to China,in the herb community in Huanglong valley,southwestern China.In total,thirty-three orchid species of 21 genera were recorded,of which 12 species are endemic to China and one is new It is interesting that so many terrestrial orchids appear in a small area（ca.1 km2）.Furthermore,some of the orchid species are dominant in the herb community.Most of the species,including orchid,have low frequency and uneven distribution patterns.The results indicated that the orchid species in Huanglong valley may disperse with regard to resource usage.Orchid species distributed mainly in two different habitats,i.e.travertine areas and the remained forest.The microenvironmental conditions and the orchid species compositions were found to be quite different between these two habitats.Travertine areas had a higher number of orchid species as well as higher numbers of orchid species per plot as compared to forest.In the travertine areas,30 orchid species were found;the most common ones being Cypripedium bardolphianum,C.flavum,C.tibeticum,G.diantha,Phaius chusua and Ph.delavayi.However,in the forested habitat,21 orchid species were found;the most common ones being T.szechuanica and Goodyera repens.Light availability seems critical to the performance and distribution of orchid species.Stream flow through the travertine area during the orchids growing season appears to be an important factor in shaping and maintaining stable microenvironments which favorable to the growth and reproduction of orchids.The results suggest that some orchid species in the travertine area would be threatened if the travertine stream flows were changed or disrupted.