甘肃白水江国家级自然保护区种子植物区系科的垂直分布格局分析

以100m为单位,将保护区内山地划分为35个海拔段,以研究保护区内科的垂直分布格局。统计分析各类分布型科的垂直分布范围、各类分布型所占比例的垂直变化,结果表明:地理分布属性在较大程度上影响着科的垂直分布,T2、T3、T8表现出与其地理分布属性相符的垂直变化趋势。原始类群集中分布于中低海拔地段;以该区为分布边缘的热带科的垂直分布范围非常狭小,集中分布于低海拔地段。热带与温带分布科的平衡线大致在海拔1500m。根据科级区系组成,对35个100m段进行了系统聚类,结果:海拔2500m是该区内科级区系成分结构沿海拔梯度变化的断点。根据各百米段聚类分析的结果,结合不同海拔的区系组成与性质的实际特点,将该山地划分为<1200m、1200～2500m、2500～3500m、>3500m四个区段。

Analysis of altitudinal distribution patterns of families of seed plants in Baishuijiang National Nature Reserve in Gansu Province

To search the altitudinal pattern of families of seed plants in Baishuijiang National Nature Reserve,the whole mountain is divided into 35 hectometre belts. Vertical distribution of families and vertical differentiation of floristic elements are analyzed. The results are as follows:(1)vertical distributions of most families are relative to their floristic characters,and vertical ranges and concentrating zones of tropical families are lower than that of temperate ones. (2)Primitive families concentrate in medium-low altitude belts. (3)tropic families that approach borders of their distribution area in the reserve exist in low altitude belts strictly. (4)floristic equilibrium point between the tropical families and the temperate ones is roughly located at the altitude of 1 500 m. The clustering analysis of the floristic composition shows that the Alt.2 500 m is the line at which family-grade floristic structure changes intensively. Based on the results of clustering analysis and the facts of floristic component and character in each altitude belts,the region can be divided into 4 sections:<1 200 m,1 200～2 500 m,2 500～3 500 m,>3 500 m.