报春苣苔的生态生物学特征

The ecological and biological characteristics of an endangered plant, Primulina tabacum Hance

报春苣苔是苦苣苔科多年生喜 Ca草本植物 ,因分布区极窄而被列为第一批国家 I级重点保护野生植物。基于其生态生物学特征探讨报春苣苔的濒危机制及解濒措施。报春苣苔生于海拔约 3 0 0 m的石灰岩山洞口附近的植物群落中 ,群落主要由一些喜 Ca及耐阴湿植物组成 ,其伴生植物为苔藓。从洞口向里 ,植物种类越来越少 ,报春苣苔的数量却越来越多 ,植株个体越来越小 ,开花的比例也越来越少。洞口的报春苣苔种群呈均匀分布 ,深处则呈集聚分布 ,洞穴的壁顶的报春苣苔群落为单一种且呈集聚分布。报春苣苔需要偏碱性的硬质水才能生长。其生存土壤太薄且营养贫乏 ,p H值为 7.5 ,有机质、全 N、全 P和全 K含量分别为 1 .8%、0 .87%、0 .1 6 %和 0 .71 % ,因而植物的生长极为缓慢 ,一般一株的年生长量为 3 0 g左右。报春苣苔分布点 CO2 平均浓度为 0 .0 9% ,高于洞外约 2倍。其相对湿度终年保持在 97%左右。报春苣苔仅生于相对弱的光环境下 ,且只在散射光线能到达的地方出现 ,大约只忍受正常光强的 1 /4以下。作为洞穴植物 ,其生态分布的限制因子是光源和特殊的大气环境。生境的特殊性导致其分布狭窄 ,3

Primulina tabacum Hance is a calciphilous perennial belonging to the Gesneriaceae family. It is narrowly distributed in northern Guangdong, and is listed in the “first class protected key wild plants of China”. The present paper presents the results of a study on the biological characteristics and ecological factors and mechanisms that have caused its endangered status, and assesses approaches for conservation. Primulina tabacum grows with other calciphilous and shade-tolerant plants (including bryophytes) around the entrances to karst caves, below 300m altitude. Variation was observed in the communities studied along gradients from the entrance to the caves, with a decrease in the number of accompanying species as the density of Primulina tabacum population increase, a decrease in the size of individuals, and a decrease in the flowering ratio of individual. Primulina tabacum populations around cave entrances show uniform distributions, whereas populations in deep caves and on the top of the caves show aggregated distributions. Primulina tabacum relies on alkalescent calciferous groundwater. The soil layer is thin and lacks nutrient, with a pH of c. 7.5; the organic content, total N, total P and total K are 1.8%、0.87%、0.16% and 0.71%, respectively. Primulina tabacum individuals consequently grow slowly, with a maximum growth of no more than 30 g/a. The concentration of CO 2 in its habitat is about 0.09%, which is approximately two times higher than outside the cave. The relative humidity is maintained c. 97%, and annual air temperatures vary from 19℃ to 21℃ through the year. Primulina tabacum only grows in environments with low light intensities, with scattered radiation of less than 25% of normal. As a species of cave plant, its limiting factors include light intensity and atmosphere environment; this specialized habitat has resulted in its narrow distribution. Human disturbance, such as tourist activities are threatening its survival. The 3 year ex situ conservation experiments have not succeed; further ecological and biological information is therefore needed, and more appropriate in situ conservation measures are necessary for its protection.