不同种植密度与修枝强度对幼龄尾巨桉生长量的影响

Effects of Planting Density and Pruning Intensity on Growth of Eucalyptus urophylla × E. grandis

为探讨尾巨桉在生产实践中不同种植密度下的适宜修枝强度,通过设置3种尾巨桉种植密度:P1(1 665株·hm^(-2),株行距:2 m×3 m)、P2(1 320株·hm^(-2),株行距:2.5 m×3 m)、P3(1 110株·hm^(-2),株行距:3 m×3 m)和3种修枝强度:不修枝、轻度修枝(修去活枝冠层1/3的下层枝条)、中度修枝(修去活枝冠层1/2的下层枝条),探讨修枝后6个月的幼龄尾巨桉生长量差异。结果表明:种植密度1 320株·hm^(-2)的平均胸径极显著高于1 650株·hm^(-2)和1 110株·hm^(-2),但种植密度1 650株·hm^(-2)的平均树高极显著高于1 320株·hm^(-2)和1 110株·hm^(-2),表明1 110株·hm^(-2)的种植密度未充分利用林地空间;中度修枝的平均胸径稍大于不修枝,表现出一定程度上促进胸径生长的作用;种植密度1 320株·hm^(-2)×中度修枝的单株材积增量最大。就尾巨桉幼龄期的生长量初步分析认为,种植密度1 320株·hm^(-2)×中度修枝是培育尾巨桉优质无节材的较适宜处理组合。

To examine suitable pruning intensities for Eucalyptus urophylla×E.grandis under different planting densities we analyzed growth of young E.urophylla×E.grandis plantations at three planting densities,which were P1 (1 665 plants·hm^(-2),spacing 2 m×3 m),P2 (1 320 plants·hm^(-2),spacing 2.5 m×3m),P3 (1 110 plants·hm^(-2),spacing 3 m×3 m) and with three pruning intensities (no pruning,slight pruning,moderate pruning).The results showed that mean DBH (diameter at breast height) of P2 was significantly higher than that of P1 and P3 whilst the mean height of P1 was significantly higher than that of P2 and P3.The results indicated that P3 under utilised the site resources.Meanwhile,mean DBH of slight pruning was slightly larger than that of no pruning and moderate pruning showed a certain trend of promoting DBH.Single tree volumes in the treatment combination P2 with moderate pruning was higher than others.Therefore,we conclude that the treatment combination of P2 and moderate pruning was the most suitable for cultivating clear wood in E.urophylla×E.grandis plantations.