民勤县荒漠—绿洲交错带梭梭种群的数量动态及分布格局

Quantity Dynamics and Distribution Pattern for Haloxylon ammodendron Population of the Desert-Oasis Ecotone in Minqin County of Gansu Province,China

通过对民勤县荒漠—绿洲交错带梭梭种群年龄结构、静态生命表、生存分析等研究来揭示种群数量动态特征;并选取6种常用聚集度指标判断梭梭种群在交错带不同区域、不同龄级分布格局变化规律。结果表明,民勤县荒漠—绿洲交错带梭梭种群以中幼林为主体,为增长型种群。存活曲线趋于Deevey—Ⅲ型;种群数量在Ⅰ～Ⅴ龄级内波动较大,个体死亡现象较多,在Ⅵ～Ⅹ龄级内种群数量趋于稳定,在Ⅹ龄级以后,个体死亡现象又开始升高,呈现衰退趋势,种群期望寿命在Ⅳ～Ⅵ龄级较高。种群分布格局总体呈现聚集分布,从绿洲边缘向沙漠边缘延伸方向,其种群分布格局无明显变化规律;随着龄级的增大,种群分布格局由聚集分布趋向均匀分布,期间有少量随机分布出现。

The research was conducted to reveal quantity dynamics characteristics with the age structures, static life table and survival analysis for Haloxylon ammodendron population of the desert-oasis ecotone in Minqin County and determine the distribution patterns in the different zones of the desert-oasis ecotone and among different age classes with six distribution indexes. The population is dominated with young and middle-aged plants, the population is close to Deevey＇ s type III, and the death phenomenon is serious in the age stage of I-V. In the age stage of VI-X, the quantity of population tends to be stable, the individual death phenomenon begins to rise again and presents recession trend after age stage of X, and the population life expectancy is higher in the age stage of IV-VI. Total population shows the clumped distribution, and there is no regular rule along the edge of oasis to the edge of desert. With the increasing of the age class, the distribution pattern is from clumped tend to uniform, and there are a few random distributions during this period.