西藏色季拉山高山松种群点格局分析

Spatial point pattern of Pinus densataforests of Sejila Mountains in Tibet

【目的】研究高山松种群不同生长阶段的空间分布格局类型及其空间关联性。【方法】2014年6-8月,在西藏色季拉山选择有代表性的区域设置50m×50m的高山松林样地4块,对样地内的高山松进行定位和每木检尺,按胸径〈12cm、≥12~〈32cm、≥32cm将高山松分为小树、中树和大树,运用点格局分析方法中的Ripley’s L函数,对高山松种群不同发育阶段的空间格局及关联性进行分析。【结果】（1）色季拉山高山松种群径级结构呈典型的＂金字塔＂型,种群自然更新良好,属增长型种群;（2）高山松不同发育阶段的分布格局各异,小树在小尺度范围内的聚集强度均明显强于中树和大树,中树主要表现为随机分布-集群分布-随机分布,而大树主要表现为随机分布;（3）样地1与样地2中,高山松小树与中树、大树之间的空间关联性基本上均呈负关联关系,但中树与大树之间基本上无关联;样地3和样地4中,高山松不同龄级的小树、中树和大树三者之间相互独立,关联性小。【结论】在从小树发育到大树的过程中,高山松种群的空间分布格局演变过程基本表现为由集群分布到随机或均匀分布;高山松种群的更新不仅受种间竞争的影响,同样受种内竞争的制约;在环境条件相似的情况下,高山松种群自身的生物、生态学特性是影响其分布格局的最主要因素。

【Objective】The spatial distribution pattern and spatial correlation of Pinus densata at different developmental stages were studied.【Method】During June to August,2014,four 50m×50mP.densataplots were set in a representative area of Sejila Mountains.Location and tally of P.densata were conducted and the P.densatatrees were divided into saplings,middle trees and large trees according to DBH values of12cm,≥12-32cm,and ≥32cm,respectively.The spatial pattern and spatial correlation of P.densataat different developmental stages were analyzed using Ripley＇s L function in point pattern analysis.【Result】（1）The demographic structure of P.densatapopulation in Sejila Mountains followed a typical＂pyramid＂shape,suggesting a high regeneration rate and good growth condition and belonging to expanding population.（2）The distribution patterns of P.densatavaried a lot at different developmental stages.The aggregation intensities of saplings at small scales were significantly stronger than those of middle trees and large trees.The spatial distribution of middle trees changed from random,aggregated,to random,while large trees showed random distribution.（3）In plots 1and 2,the spatial correlations between saplings and middle trees and between large trees were negative,and there was no correlation between middle trees and large trees.In plots 3and 4,saplings,middle trees,and large trees at different ages were independent with less correlations.【Conclusion】During the growth process of P.densata population from saplings to large trees,the spatial pattern developed from aggregated to random or uniform distribution.The regeneration of P.densatapopulations depended on interspecific relationship and intraspecific relationship.The spatial pattern of P.densatapopulation in this area with uniform environment conditions was controlled by biotic interactions and ecological characteristics.