北京市紫椴种群空间分布格局研究

Study on spatial distribution pattern of Tilia amurensis population in Beijing

【目的】揭示北京市紫椴种群空间分布格局的形成机制、种群分布规律和动态变化。【方法】在北京玉渡山和雾灵山设置有代表性的紫椴样方(20m×20m)12个,按照胸径(DBH)将样方内的紫椴划分为幼树(0cm<DBH≤8cm)、小树(8cm<DBH≤16cm)、中树(16cm<DBH≤24cm)和大树(DBH>24cm)4个年龄阶段,应用偏离指数、Morisita指数、扩散系数及负二项参数、Cassie指标、平均拥挤度和聚块性指标等聚集强度参数,分析不同生长阶段和不同尺度(1m×1m,2m×2m,2m×4m,4m×4m,5m×5m,5m×10m,10m×10m)下紫椴种群的格局类型及聚集强度,并采用双项轨迹方差法(TTLV)分析其格局规模。【结果】大多数样方中的紫椴均呈聚集分布。在"幼树-小树-中树-大树"的生长过程中,紫椴种群均为聚集分布,但聚集度由大变小。聚集强度随取样尺度的变化而变化,在5m×5m的取样尺度下聚集强度最大;空间分布的小斑块直径为35m,大斑块直径为270m。【结论】紫椴种群的分布格局以聚集分布为主,随着林层的增高由聚集分布逐渐向随机分布过渡。种群管理应以聚集规模为依据,促进团块状更新,保持种群的聚集性生长,还需加强对幼树的抚育和对老龄个体的病虫害防治。

【Objective】The purpose of this study is to reveal the spatial distribution pattern and its formation mechanism and dynamic of the Tilia amurensis population in Beijing.【Method】12 representative plots of Tilia amurensis in Yudu and Wuling Mountain in Beijing were chosen,and four age phases according to the diameter at breast height（DBH）were divided：seedlings（0cmDBH≤8cm）,small trees（8cmDBH≤16cm）,middle-aged trees（16cmDBH≤24cm）and adult trees（DBH24cm）.The pattern types and intensity on different sampling scales（1m×1m,2m×2m,2m×4m,4m×4m,5m×5m,5m×10m,10m×10m）and various growth stages,with the application of deviation index,Morisita index,Cassie index,clumping index,negative binomial parameter,mean crowding index and index of patchiness were performed.We also use two-term local variance（TTLV）to analysis the pattern scale of the population.【Result】The results show that the pattern is cluster distribution in most plots.In the process ofgrowing from seedlings to young trees and adult trees,the population transition from cluster distribution to random distribution with the decreasing of aggregation intensity.Aggregation intensity of the population relies on the change of sampling scale,and it reaches the highest value under the scale of 5m×5m.The diameter of small patches of the population is 35 m while the large patch is 270 m.【Conclusion】Cluster distribution is the main pattern of this population,and it transfer to random pattern when the growth stage upgraded.As to its management,we suggest to keep the cluster of populations,strengthen seedling and young trees,and control plant diseases and insect pests of older individuals.