甘肃敦煌西湖多枝柽柳群落特征和种群格局

Community characteristics and population patterns of Tamarix ramosissima in Dunhuang Xihu of Gansu Province,northwestern China

为阐明多枝柽柳的群落特征和种群格局,选择甘肃敦煌西湖国家级自然保护区作为调查地点,在2006年10月和2007年6月分别调查了35个20m×20m的样方,采集了经纬度、海拔和土壤类型等环境因子数据,运用物种丰富度指数、物种多样性指数和物种均匀度指数等多样性指标及丛生指标、平均拥挤度、聚块性指数、扩散系数和负二项参数等聚集强度指标进行分析。结果表明:多枝柽柳群落中共记录植物20种,分属12科19属,其中,灌木层8种,分属5科8属,草本层12种,分属7科11属;该群落可划分为4个群丛组:Ⅰ多枝柽柳-芦苇群丛组;Ⅱ多枝柽柳+苏枸杞群丛组;Ⅲ多枝柽柳+盐节木群丛组;Ⅳ多枝柽柳沙包群丛组。多枝柽柳群落的物种丰富度指数为0.375,物种多样性指数为0.330,物种均匀度指数为0.487。从群丛组间比较来看,物种丰富度指数和物种多样性指数呈现相同的分布规律,依次为Ⅲ>Ⅱ>Ⅰ>Ⅳ;物种均匀度指数依次为Ⅲ>Ⅳ>Ⅱ>Ⅰ。从指数间的相关性分析来看,物种多样性指数与物种均匀度指数呈极显著正相关,相关系数达0.920(α<0.01)。种群格局分析表明,多枝柽柳和共建种芦苇的种群空间分布都呈显著的聚集分布,且芦苇对空间的侵占和填充能力要强于多枝柽柳。

In order to illustrate the community characteristics and population patterns of Tamarix ramosissima in Dunhuang Xihu National Nature Reserve of Gansu Province,northwestern China,we investigated environmental factors,i.e.latitude,longitude,elevation and soil types in 35 quadrats （20 m × 20 m） from October 2006 to June 2007,by using three diversity indices,i.e.the Margalef’s richness index,Simpson’s diversity index and Pielou’s evenness index,as well as the methods,such as a clump index,mean crowding index,index of patchiness,dispersion coefficient and negative binomial parameter.There were 20 species in the T.ramosissima community,belonging to 19 genera and 12 families,of which 8 shrub species belong to 8 genera and 5 families and 12 grass species belong to 11 genera and 7 families.The T.ramosissima community was sorted into four association groups： Ⅰ Ass.Group T.ramosissima ＋ Phragmites communis,Ⅱ Ass.Group T.ramosissima ＋ Lycium ruthenicum,Ⅲ Ass.Group T.ramosissima ＋ Halocnemum strobilaceum and Ⅳ Ass.Group T.ramosissima sand dune.The value of the Margalef’s richness index was 0.375,the Simpson diversity index 0.330 and Pielou’s evenness index 0.487.The Margalef and Simpson indices showed the same distribution patterns among the four groups,both in the following order： Ⅲ Ⅱ Ⅰ Ⅳ,while the order of Pielou’s evenness index was： Ⅲ Ⅳ Ⅱ Ⅰ.Simpson’s diversity index showed a significantly positive correlation with Pielou’s evenness index,with a correlation coefficient of 0.920 （α 0.01）.The populations of T.ramosissima and P.communis both appeared as clumped distributions,of which the P.communis population showed stronger invasive and recruitment capacity compared with T.ramosissima.