珍稀植物银砂槐中国分布区的种群结构与动态分析

Structure and Dynamics of China Rare Plant Ammodendron bifolium(Pall.)Yakovl Natural Population

通过对中国唯一银砂槐（Ammodendron bi folium）分布区——新疆伊犁河谷地塔克尔莫乎尔沙漠狭窄区域的样地调查和数据统计分析，绘制了银砂槐自然种群的径级结构图，编制了种群的特定时间生命表，分析了存活曲线、死亡率曲线和寿命期望等重要参数，并运用时间序列模型预测种群数量动态。结果表明：（1）研究区内银砂槐种群结构中小径级个体较多，即I～Ⅲ径级占70．4％，Ⅳ～Ⅶ径级占27．62％，Ⅷ～X径级仅占1．98％，种群整体结构属于增长型，但I径级个体数少于Ⅱ径级，种群的自然更新相对较差。（2）静态生命表分析结果表明，随着径级的增加银砂槐种群死亡率大致为上升趋势，且种群内基径超过3．5cm（Ⅷ径级）的银砂槐数量迅速下降，即研究区内银砂槐基径越接近Ⅷ径级就越接近其生理寿命。（3）研究区内银砂槐的存活曲线基本接近DeeveyⅢ型，但I径级存活数低于Ⅱ径级，Ⅱ径级后存活数量迅速下降，说明该种群幼苗补充量较少，自然更新受阻。（4）时间序列分析表明，随着时间推移，种群未来会呈现老龄个体增加的趋势。研究认为，新疆伊犁河谷地的银砂槐种群的生长发育主要受限于其自身的生物学特性和种内竞争，其种群的长期稳定维持较为困难，现有植株及生境斑块的妥善保护和适当的人工辅助措施是该区银砂槐种群恢复的关键。

Through a field investigation and data analysis to the only distribution area of Ammodendron bi- folium population in Takeermohuer Desert of the Ili River valley in Xinjiang,we aimed to learn the actuali- ty of A. bifolium population,and forecast the future dynamics of A. bifoliurn population. In this research, the size structure glife tables, survival curve, mortality curve and life expectancy of A. bifolium population were studied and population dynamics were predicted by a time-sequence model. The results show that.（1） The small-sized individual in A. bifolium population were more,namely the number of I ~ Ill diameter in- dividuals accounted for 70.4% ,the number of Ⅳ-Ⅶ diameter individuals accounted for 27.62% ,the number of Ⅷ- X diameter individuals accounted for only 1.98%. Therefore, population structure belongs to the growth type. However,the number of I diameter individuals was less than that of Ⅱ diameter individu als,so that the natural regeneration of A. bifolium population was poor. （2）The static life table analysis show that A. bifolium population mortality was on a rising tendency, and the number of the individuals with diameter more than 3.5 cm （Ⅷ diameter） decreased rapidly with the increase of diameter grade,namely the individual closing to Ⅷ diameter was more close to the physiological longevity. （3）The survival curve of A. bifolium population mainly belonged to Deevey Ill type in research area. The survival number of [ diameter individuals was less than that of lI diameter individuals,and the survival number after ]~ diame- ter individuals decreased rapidly, It indicated that the population was lack of seedling transshipment and natural regeneration was blocked. （4）Through time-sequence prediction, the population in the future would be more aging individuals. The studies suggest that A. bifolium population growth in the Ili River valley of Xinjiang was mainly limited to its biological characteristics and intraspecific competition. Thus,it was diffi- cult for A. bifolium population to maintain the stability. As a result,the crucial factors for the natural re- generation and restoration of A. bifolium population in research aera are the protection of living individuals and their habitat and the revegetation by human.