长白落叶松树冠半径分布特征及其对竞争的响应

The Distribution Characteristics of Crown Radius and Its Response to Competition of Larix olgensis

[目的]研究林木树冠形态对外界环境适应的可塑性机理。[方法]以小兴安岭地区的长白落叶松为研究对象,利用详细的树冠半径调查数据,研究长白落叶松的树冠偏冠现象,分析树冠偏冠与林木大小和竞争之间的关系。[结果]在单木水平上,不同林龄样地中林木的树冠变异系数的平均值均大于20%,大部分林木的树冠半径变异系数较大,只有不到1/5的林木的树冠半径变异系数小于15%。不同林龄样地中长白落叶松偏冠距离的平均值在0.35~0.51 m之间,各样地中林木偏冠距离的最大值均在1.2 m以上,其中成熟林中林木偏冠距离的最大值达到1.73 m。树冠的偏冠方向没有特定的方向偏向,是均匀分布的。在幼龄林中,林木的偏冠距离与胸径、冠长、平均树冠半径呈显著正相关,树冠偏冠距离随树木增大而增大。在中龄林和近熟林中,偏冠指数与胸径、树高和平均树冠半径呈显著负相关,与高径比呈显著正相关,树冠偏冠程度随树木增大而减小。在成熟林中,偏冠程度与林木大小的相关性不显著。在幼龄林、中龄林、近熟林中,树冠偏冠与竞争压力呈显著正相关,在成熟林中树冠偏冠与竞争压力的相关性不显著。基于树冠中心坐标计算的林分平均竞争指数均小于基于树干坐标计算的林分平均竞争指数。[结论]长白落叶松树冠偏冠距离一般随着林龄的增大而变大,在不同发育阶段受到不同程度竞争的影响,树冠偏冠在一定程度上降低了林分平均竞争指数,减少了林分竞争压力。

[Objective]To study the plasticity mechanism of tree crown morphology adapting to the external environment.[Method]Taking Larix olgensis in Xiaoxing'anling Mountain as the research object,using detailed crown radius survey data,the phenomenon of crown displacement of L.olgensis was studied,and the relationship between crown displacement and tree size and competition was analyzed.[Result]At the level of individual tree,the average value of the crown radius variation coefficient of trees in sample plots with different ages was larger than 20%,and the crown radius variation coefficient of less than 1/5 trees was less than 15%.The average value of crown displacement distance of L.olgensis was between 0.35~0.51 m in the plots with different ages.The maximum value of crown displacement distance of trees in all plots was more than 1.2 m,and the maximum value of crown displacement distance of trees in mature forest was 1.73 m.No specific direction deviation was observed in the direction of crown deviation,which was evenly distributed.In the young forest,the crown displacement distance was significantly and positively correlated with DBH,crown length and average crown radius,and the crown displacement distance increased with the increase of trees.In the middle-aged forest and near mature forest,the crown displacement index was negatively correlated with DBH,tree height and average crown radius,and positively correlated with height diameter ratio.In mature forest,the correlation between crown displacement and tree size was not significant.In young forest,middle-aged forest and near mature forest,there was a significant positive-correlation between crown displacement and competitive pressure,but there was no significant correlation between crown displacement and competition index in mature forest.The average competition index calculated based on crown center coordinate was less than that calculated based on stem coordinate.[Conclusion]The crown deviation distance of L.olgensis generally increases with the increase of forest age,and is affected by different degrees of competition at different development stages.The crown displacement will reduce the average competition index and the competition pressure of the stand to a certain extent.