濒危植物秦岭石蝴蝶的生态学特性及濒危原因分析

通过野外调查和随机取样法,对仅产于陕西勉县的中国特有濒危植物秦岭石蝴蝶( Petrocosmea qinlingensis W. T. Wang)群落的维管植物组成、垂直结构和分布区类型及其种群特征和土壤化学性质进行了调查和分析；在此基础上,初步探讨了该种类的濒危原因。调查结果显示：秦岭石蝴蝶为喜阴植物,仅分布于山体海拔约640 m的区域,种群面积仅约42 m2；土壤为黄棕壤,呈中性(pH 6.50),土壤中有机质含量较高,全氮、全磷和全钾含量较低,有效铁、有效镁、有效钠和有效钙含量则较高；秦岭石蝴蝶种群中个体数量约1000株,多生长于覆有土壤或苔藓的岩石上,也有部分成年个体生长在裸露且瘠薄的岩石上。秦岭石蝴蝶群落中共有维管植物28种,隶属于23科28属；其中,蕨类植物3科4属4种,裸子植物1科1属1种,被子植物19科23属23种,优势科和优势属不明显。秦岭石蝴蝶群落垂直结构明显,可分为乔木层、灌木层和草本层,其中,乔木层优势种为杜仲( Eucommia ulmoides Oliver),灌木层优势种为华西小石积( Osteomeles schwerinae Schneid.),草本层优势种为裂叶荨麻( Urtica lobatifolia S. S. Ying)。该群落维管植物科的分布型以热带分布型科为主,其中泛热带分布型科占明显优势；属的分布型以温带分布型属为主,其中北温带分布型属占优势；中国特有分布的科和属均很少；总体上看,该群落具有暖温带向亚热带过渡的特点。在秦岭石蝴蝶种群的不同样方中,成年个体和幼苗数量均有一定差异,成年个体占14.6%~37.5%,幼苗占61.3%~80.0%,幼苗数量明显高于成年个体；各样方的单株叶片数为7~9,冠幅为6.0~7.2 cm,大多数样方的单株结实量小于4,表明在同一个种群的不同生境中秦岭石蝴蝶的分布和生长状况有明显差异。根据调查结果,推测种群规模较小、分布范围狭窄以及人为干扰可能是造成秦岭石蝴蝶濒危的主要原因,而人为干扰是其中的重要原因。

Analyses on ecological characteristics and endangered reason of endangered plant Petrocosmea qinlingensis

By field survey and random sampling method, vascular plant composition, vertical structure and distribution type of community of Petrocosmea qinlingensis W. T. Wang, an endemic endangered species in China and only distributing in Mianxian County of Shaanxi Province, and its population characteristics and soil chemical property were investigated and analyzed. On this basis, endangered reason of P. qinlingensis was preliminarily discussed. The investigation results show that P. qinlingensis is shade-acclimated plant, and only distributes in the district of the mountain with altitude about 640 m. Area of P. qinlingensis population is only about 42 m2 . The soil is yellow brown soil and is neutral (pH 6. 50). Content of organic matter in soil is higher, contents of total nitrogen, total phosphorus and total potassium are lower, and contents of available iron, available magnesium, available sodium and available calcium are also higher. Number of individuals in P. qinlingensis population is about 1 000, most grow on the rock covered with soil or moss, and some adult individuals grow on naked and barren rock. There are 28 species of vascular plants in P. qinlingensis community, which belong to 28 genera in 23 families, in which, there are 4 species of pteridophyte belonging to 4 genera in 3 families, 1 species of gymnosperm belonging to 1 genus in 1 family, 23 species of angiosperm belonging to 23 genera in 19 families, and dominant families and genera are not obvious. Vertical structure of P. qinlingensis community is obvious and can be divided into arbor, shrub and herb layers, in which, Eucommia ulmoides Oliver is dominant species in arbor layer, Osteomeles schwerinae Schneid. is dominant species in shrub layer, and Urtica lobatifolia S. S. Ying is dominant species in herb layer. Distribution type of family of vascular plants in this community is mainly tropical distribution type family, in which, Pantropic family takes an obvious advantage;distribution type of genus is mainly temperate distribution type genus, in which, N. Temp. genus takes an obvious advantage;there are a few families and genera belonging to Endemic to China. On the whole, P. qinlingensis community has the feature of warm temperate zone transition to subtropical zone. There are a certain differences in numbers of adult individual and seedling in different quadrats of P. qinlingensis population, with adult individual accounting for 14. 6%-37. 5%and seedling accounting for 61 . 3%-80 . 0%, showing that number of seedling is obviously higher than that of adult individual. Leaf number per plant in different quadrats is 7-9, crown width is 6. 0-7. 2 cm, and fruit setting amount per plant in most quadrats is less than 4. It is indicated that there are obvious differences in distribution and growth status of P. qinlingensis among different habitats in the same population. According to investigation results, it is speculated that small population size, narrow distribution range and human disturbance are the main reasons for causing P. qinlingensis to be endangered, in which, human disturbance is the most important reason.