肃北地区稀有植物裸果木种群的空间分布格局

为了探索肃北荒漠地区裸果木种群分布格局、成因和维持机制,根据植被类型、地形地貌和海拔,选择了6个样地,共随机设置60个样方,应用方差/均值、负二项参数、扩散型指数、丛生指标、平均拥挤度指数和聚块性指数、Poisson分布等方法,采用Kolmogogorov-Smirnov检验进行显著性检验,分析在不同样地、不同海拔下的裸果木种群空间分布格局。研究表明,在红柳峡干沟和一棵树干河床地带,裸果木种群呈集聚分布,集聚原因主要是由于与裸果木克隆生长特性及其对恶劣环境的适应性密切相关。在芦草沟和干沟口子山前干河床地带,裸果木种群为随机分布,是由于裸果木自身有性繁殖力衰退,幼龄的植株少,中老龄植株多,各物种间和裸果木种内的竞争是主要原因,还受地形地貌、生境、洪水和泥石流等自然灾害的影响。野马河种群是随机分布与集群分布的混合类型,各物种间和裸果木种内竞争造成其随机分布,而强烈的洪水和泥石流冲刷作用促成集群分布。马鬃山金庙井种群为集群分布,但集聚程度并不高,集聚原因跟其生境和土壤有关。由于这一地带地处洪积扇平原,地势平坦,上游裸果木的种子随着洪水的缓缓冲刷和泥沙的淤积,沉积在这一带,是造成这一地区裸果木集群分布的原因。依据海拔来看,在1500~1550m区段,为集群分布,但集聚程度并不高。海拔在2400~2450和2450~2500m区段,均为随机分布,是肃北裸果木的集中分布区。海拔在2700~2750m区段,属于集群与随机混合型分布格局。裸果木在肃北地区的种群空间分布格局是由自身的繁殖特性和自然灾害两大主要因素共同作用的结果,同时与其他生物特性、环境因子和人为因素也密切相关。

The spatial distribution patterns of rare plant Gymnocarpos przewalskii communities in Subei

In order to explore the spatial patterns of Gymnocarpos przewalskii in the Subei desert, as well as its causes and maintenance mechanisms, 60 quadrats are randomly set according to the vegetation types, the topography, geomorphology and the different altitudes. The variance/mean ratio, parameter of negative binominal, dispersal index, index of clumping, index of mean crowding, index of aggregation and index of patchiness, poisson distribution method are used to analyze the spatial distribution patterns and Kolmogogorov-Smirnov test for significance test. The results show that the population distributions of the G. przewalskii are contagious distribution at the dry beds of Gangou and One tree; taking on random distribution at the foreland dry bed areas of Lucaogou and Gangoukouzi, which is due to intense competition between middle-old plants against the background of their sexual reproductive decline and lack of seedlings; The intermediate type between random and contagious distribution at Yema River, which is due to the combined affect of intraspecies and interspecific competition, and the scouring of forceful deluge and mud-rock flow, coming close to contagious distribution at Jinmiaojing in Mazong mountain area, the reason of contagious distribution was related with its ecosystem environment. The seeds of G. przewalskii silted gradually in this area with eroding by flood and filling by silt because of which lies in puluvial fan plain. All of this caused the contagious distridution of G. przewalskii in the area.From the altitude standpoint, the population distributions of the G. przewalskii is weak contagious distribution at 1 500-1 550 m, random distribution at 2 400-2 450 and 2 450-2 500 m where mostly living from the Subei desert; the intermediate type between random and at 2 700-2 750 m. The spatial patterns of G. przewalskii in the Subei desert result from the major affect of its propagation characteristics and natural disaster, together with other factors, such as Human activity and environmental factors.