毛竹扩张过程中竹与树空间关系的点格局分析

Point pattern analysis for spatial association between bamboo and trees during Phyllostachys edulis expansion into broad-leaved forest

毛竹与树木相互作用关系是解释毛竹扩张的关键。在井冈山自然保护区选取典型竹阔界面样地(50×100 m)调查样地内毛竹和树木的植株空间分布距离,采用Programita软件对树木与毛竹、毛竹母竹与新竹的空间关联性进行O-ring统计分析:结果发现:(1)0—100 m的整个界面区域,毛竹与树木在0—10 m任何尺度都是负关联。由毛竹纯林向混交林过渡,毛竹与树木的负相关距离加大,由2—3 m增加到2—9 m;(2)毛竹与不同生态型树木的空间关联性表现出较大差异,无论在任何区域,从0—10 m尺度上毛竹与落叶树都无关联,但在0—100 m整个界面区域,除<1.0 m尺度外,毛竹与常绿树是负关联;扩张前期(前沿区)毛竹与乔木的负相关距离比与灌木树的大;(3)毛竹母竹与新竹在不同时期不同区域的空间关联性有较大差异,在0—40 m区域内,仅2013年在1 m尺度下母竹与新竹呈正关联,在40—80 m区域内,随扩张年份增加,母竹与新竹关联尺度距离由2007年的6—7 m下降到2013年1 m和3—6 m。结果表明毛竹与树木间存在明显的相互排斥作用,竹与树的作用强弱与树木的生态型特征、扩张阶段和二者相对密度有关。毛竹扩张方式可表现为前期远距离放置新竹,扩张后期进行密度填充。研究结果可为竹子扩张程度判定及扩张预测、防控提供参考。

Understanding the interaction between bamboo and tree is required to explore the expansion of Moso bamboo(Phyllostachys edulis).In this study,we collected the spatial information of all individuals from a typical bamboo and broad-leaved forest interface(50×100 m)in Jingangshan National Nature Reverse,Jiangxi Province,China.Further,we used Programita software to analyze the spatial association between trees and bamboos,parent culms and new culms through O-ring statistical analysis.The results were as follows.(1)Bamboos were negatively associated with trees at all scales(within 10 m)in the whole interface.The range between bamboos and trees increased from 2-3 m in the bamboo forest to 2-9 m in the mixed forest.(2)Bamboos had variant associations with trees with different life ecotypes.They had no association with the deciduous tree species at any scale in the interface anywhere,while in 0-100 m interface,they were negatively correlated with trees at all scale except the scale of less than 1 m.Moreover,the scale that bamboos were negatively correlated with trees was larger than that with shrub in the early expansion stage,i.e.the front of bamboo expansion.(3)Associations between parent culms and new culms varied with expansion stage and forest interface.In 0-40 m zone of bamboo and broad-leaved forest interface,parent culms were positively correlated with young culm only at the scale of 1 m in 2013.In 40-80 m zone of the bamboo and broad-leaved forest interface,the range between the between parent culms and new culms decreased from 6-7 m in 2007 to 1 m and 3-6 m in 2013.The findings reveal that there is a significant negative association between bamboos and trees,and the association depends on the ecotype of trees,expansion stage as well as the relative density of both trees and bamboos.Bamboos expand into the broad-leaved forests through long-distance establishment of the new culms in the early expansion stage and the gradual population density increase in the late stage.The work can provide references not only for the determination extension and predictions of bamboo expansion,but also for the forest management to prevent from bamboo expansion.