异质光环境中光皮桦树冠形状的可塑性

摘要

树冠形状是树木对环境适应能力及生长发育形态的综合表现,是树木生长过程中与环境共同作用的结果,分析异质光环境中树冠形状的可塑性,可为林木的抚育经营提供科学依据.以黔中白云岩山地生长的光皮桦天然林作为研究对象,对孤立木、林缘木和林中木3种不同光环境中的光皮桦树冠形状可塑料性进行测定分析.结果表明,树冠形状指数的变化中,冠长率变化从孤立木、林缘木到林中木均逐渐下降,伸展度的变化表现出同样的变化规律,而圆满度和投影比的变化差异不显著,揭示了光皮桦树冠主要通过减小树冠的长度和宽度,来适应异质光环境的变化,而对圆满度和投影比的变化影响不明显;在树冠表面积指数和体积指数的变化中,其大小差异均未达到显著水平,反映了光皮桦树干的单位地径横断面所需的树冠表面积,单位材积所需的树冠体积受光环境的影响不明显.%Crown shape is a comprehensive performance to adapt to environment and growth form.It is the result of interaction about tree growth and environment.The analysis of canopy plasticity in heterogeneous light environment can provide scientific basis for forest management.Taking Betula luminifera at dolomite mountains in central Guizhou as object,the plasticity changes of the crown shapes of isolated trees,forest edge trees and centre trees of within the forest were measured.The results showed that the crown length ratio and the stretch ratio of these three trees gradually decreased.There are no significant difference of the fullness ratio and projection ratio.It was found that B.luminifera could adapt the change of the light through reducing the length and the width of the canopy.There were no significant difference of the crown surface area index and volume index.Light environment could not affect the area ratio of crown to ground diameter and the volume ratio of crown to trunk.