塔里木河干流胡杨种群结构与分布格局研究

Population Structure and Spatial Distribution of the Populus euphratica in the Mainstream of the Tarim River

采用样方法对塔里木河干流上、中、下游胡杨(Populus euphratica)种群按径级、高度级、长势级进行实地调查与统计,绘制径级结构图、高度结构图和长势结构图,并应用理论分布模型和聚集强度指数进行种群分布格局分析。结果表明:(1)塔里木河干流胡杨径级结构呈"纺锤型",幼苗和幼树缺乏(Ⅰ～Ⅱ级占28.83%),以Ⅲ～Ⅴ级占绝对优势(占66.62%),老龄植株所占比例最低(Ⅵ级占4.55%),从龄级结构看种群处于衰退的早期阶段,存活曲线符合DeeveyⅠ(凸)型,为稳定种群。(2)塔里木河上游胡杨种群高度级比例差异小(变幅为21.60%～31.07%),处于发展阶段;中游种群结构呈正态分布,为稳定增长型;下游种群高度级比例差异大(变幅为12.50%～51.14%),处于衰退阶段。(3)塔里木河干流胡杨种群分布格局呈聚集分布,不同离河距离的胡杨种群聚集强度有差异,不同龄级的胡杨种群聚集强度也不同,幼树的聚集程度高,Ⅵ级聚集强度较其他龄级差。

The main purpose of this study is to examine the fluctuation characteristics of natural Populus euphratica community.Field data were obtained by tally with contiguous grid quadrat method.Investigated contents include the community structure,dominant species,and the height structure,growth vigor and diameter structure of P.euphratica.Finally,the population structure and distribution pattern of P.euphraticain desert riparian forest were discussed on the basis of theoretical distributing model and assembling intensity index.The results shows：（1）The DBH class allocation of the P.euphratica populations mainly concentrated on the middle DBH class;Ⅲ～Ⅴclass was 66.62%;the seedling and young tree are insufficient;Ⅰ～Ⅱclass was 28.83%andⅥclass was 4.55%;the population spatial structure were not of integrity.It indicated that population show a decline stage in the early.The survivorship curve of the population conformed to the type of DeeveyⅠ.（2）The height class structure of P.euphraticapopulation had little difference,with range of 21.60%～31.07%,which belonged to growth-oriented population in the upper reaches of Trim River.The diameter class structure showed approximately normal distribution,which shows that the overall population is steadily increasing in middle reaches of Tarim River.The height class structure had great difference,with range of 12.50%～51.14%,the distribution of the diameter class was shown as a negatively skewed distribution,which belonged to stable type population.（3）The ground survey analysis indicated that P.euphraticadistribution pattern shows aggregated distribution in the mainstream of the Tarim River,the aggregation intensity was different at various distance away from the river.P.euphratica was aggregated distribution in different stages and the aggregation intensity was different.The variations in spatial distribution patterns of populations in different habitats and at different growth stages were closely related to the biological and ecological characteristics of the species.