城市景观红竹林立竹冠形结构特征

对景观红竹林2007-2009年立竹的胸径、枝夹角、枝分角、冠长、冠幅、枝盘数进行了调查分析。结果表明:立竹冠长、冠幅、枝盘数与立竹胸径分别呈3次、2次多项式和线性关系;当立竹密度45023株/hm2以下时,不同年龄立竹不同竹冠部位的枝夹角无显著差异,立竹密度为26713株/hm2时,立竹不同竹冠部位的枝分角差异极显著;试验林立竹密度范围内,立竹密度对枝夹角、相对竹冠长无显著影响,对枝分角、相对冠幅、相对枝盘数有一定的影响。随着立竹密度的增大,竹冠上部枝分角显著下降,竹冠中部、下部枝分角呈先升后降趋势,相对冠幅、相对枝盘数呈下降趋势。当立竹密度为60030株/hm2时,枝分角、相对冠幅、相对枝盘数显著下降,对竹林的更新生长已产生不利影响。

Characters of Crown Structure of Phyllostachys iridenscens for Urban Landscape

To study the variation law of crown structure of Phyllostachys iridescens forest with different ages and provide the theoretic basis for human disturbance of Ph.iridescens forest for urban landscape, the Ph.iridescens forest without human disturbance which was established with high density and total height in 2005 was investigated for diameter at breast height （DBH）, branch angles, angles between branches, crown length, crown width, number of branches between 2007-2009. It was found that the crown length, crown width and the number of branches were the subsidiary factors of DBH, and had quadratic polynomial, cubic polynomial and linear relationship with DBH, respectively. No significant difference was found among the branch angles at different parts of crown of standing bamboo at different ages when stem density was below 40523 stems/hm2, and significant difference was found among the angles between branches at different parts of crown when stem density was 26713 stems/hm2. The density of experimented bamboo forest had no significant impact on the branch angles and the relative crown length but a certain impact on the angles between branches, the relative crown width and number of braches. With the increasing of density, the angles between branches at upper crown decreased significantly, while those at middle and bottom crown represented the ascending and then declining trend, and the relative number of branches and the crown width decreased. When stem density was 60030 stems/hm2, the angles between branches, the relative number of branches and the crown width declined significantly, which had negative influences on the growth and regeneration of bamboo forest.