海南龙血树种群的年龄结构及分布格局

通过调查石灰岩及花岗岩两种不同生境样地内海南龙血树分布和胸径/基径情况,分析其龄级结构,用相邻格子法对海南龙血树进行每木调查,并采用方差/均值比率法和丛生指数(I)、负二项参数(K)、平均拥挤度(m*)、聚块性指数(PAI)、聚集指数(Ca)等聚集强度指数对海南龙血树种群分布格局进行分析。结果表明:石灰岩及花岗岩样地内的海南龙血树种群皆呈衰退型,其中天安乡、江边乡两样地种群的幼苗储备不足,昌化镇及东澳镇两地的中龄级植株数量稀少,大小洞天样地的种群年龄结构不完整;石灰岩样地内的海南龙血树种群在不同尺度、不同阶段上主要表现为集群分布,花岗岩地区种群的不同组分在不同取样尺度上分布格局相同,幼龄树、中龄树、老龄树的分布格局分别为集群分布、均匀分布、集群分布。

Age Structure and Distribution Pattern of Dracaena cambodiana Different Habitats

Adjacent lattice method was used to study the age structure and distribution pattern of Dracaena cambodiana the limestone and granite habitats.At different scales,aggregation intensity index such as variance/mean ratio and deviation index(Cx),negative binomial parameter(K),clumping index(I),mean crowding index(m*),poly index(PAI)and aggregation index(Ca)were used to analyze the distribution patterns.The results showed that the age structure of D.cambodiana limestone and granite presented a tendency tower declining and the age structure of the populations in Daxiaodongtian was incomplete.The number of young trees in Tianan town and Jiangbian town was apparently insufficient,and the mature trees in Changhua town and Dongao town were scarce.Populations in the limestone habitats presented a cluster distribution at different scales and different age,while the distribution patterns of different components in the granite habitats were the same on different sampling scales.The distribution patterns of young trees,mature trees and old trees were cluster distribution,uniform distribution,and cluster distribution,respectively.