湘西北长果安息香种群数量与分布格局

对湖南石门壶瓶山景关门、桑植龙潭坪茅垭村样地的长果安息香(Changiostyrax raxdolichocarpa)种群数量和分布格局进行调查和分析。结果表明：长果安息香种群的年龄结构呈衰退型，个体数量主要集中在小树(IV龄段)，幼龄级株数和老龄级株数匮乏；长果安息香种群在进入生理死亡年龄前有2个死亡高峰，第1个峰值产生于幼树(II、III龄段)，主要原因是种内和种间竞争(主要是光照)，第2个峰值产生于中树长成大树阶段(V、VI龄段)，除种内、种间对环境的竞争外，生长地土层浅薄、大树倒伏及人为砍伐亦加剧了该峰值的产生；种群整体呈聚集分布类型，小树向中树、大树变化过程表现出聚集分布向随机分布转变，导致长果安息香濒危的主要原因是种子萌发率极低、种群竞争能力较差以及人为干扰等。

The population quantity and distribution pattern of the endangered plant Changiostyrax raxdolichocarpa

The population quantity and distribution pattern of Changiostyrax raxdolichocarpa in Hupingshan and Sangzhi, Hunan province, were investigated and analyzed. Age structure analysis showed the population of Changiostyrax raxdolichocarpa was a declining one, in which there were mainly small trees (IV age group) with infant and old trees lacked. Before entering the physiological age of death, there were 2 mortality peaks of Changiostyrax raxdolichocarpa, one of the which was in the young trees stage (II, III age groups) caused by intraspecific and interspecific competition (mainly for light) and the other was in the stage of the trees growing into big ones (V, VI age groups). Besides, shallow soil, lodging of big trees and man-made cutting intensified the peaks. The whole population presented a gathering distribution, in which sapling trees distributed in a gathering way and big ones in a random way. Through investigation we found that the reasons causing Changiostyrax raxdolichocarpa endangered were low seed germination rate, less competitiveness and Man-made interference etc.