修枝对辣木株高-地径异速生长关系的影响

Effects of pruning on allometric relationship between height and basal diameter of Moringa oleifera

株高-地径异速生长关系反映了不同环境压力下树木在垂直和水平生长之间的权衡,了解修枝对株高-地径异速生长关系的影响,有利于探索环境压力对树木资源分配的作用机制。本文以辣木(Moringa oleifera)为对象,研究了修枝对辣木生长以及株高-地径异速生长关系的影响。结果表明:修枝50%、修枝100%以及修枝100%+去顶对辣木株高和地径生长有显著抑制作用(P<0.05)。但测定后期(12和16周)修枝50%和对照处理的株高差异不显著(P>0.05),修枝50%和修枝100%的地径生长速率高于对照处理,表明辣木在修枝后可能存在生长补偿机制。一般线性模型(GLMs)和标准化主轴法模型(SMA)对株高-地径拟合的决定系数相同,但是前者计算出的异速生长系数低于后者(前者为后者的84.9%~91.9%)。辣木异速生长系数随着修枝程度加大而升高,去顶处理降低了系数,表明修枝会促进辣木将更多的资源分配到株高生长,而地径增粗受到限制,去顶则相反。生产中,推荐采用修枝50%的方式对辣木进行田间管理。

Allometric relationships between height and basal diameter reflect the tradeoff of resource allocation between vertical and horizontal growth in trees under different environmental conditions. Understanding the effects of pruning on the allometric relationship between height and basal diameter can contribute to exploring the tree resource allocation mechanism under environmental stress. This study investigated the effects of pruning methods on growth and allometric relationship between height and basal diameter of Moringa oleifera in Yuanmou dry and hot valley. The results showed that there were significant differences in height and basal diameter among pruning 50%, pruning 100%, pruning 100%＋topping and control treatments （P〈0.05）. At the late stages of measurement （ 12 and 16 weeks）, there was no significant difference in height between pruning 50% and control treatments （P 〈 0.05 ） and the growth rates in basal diameter of pruning 50% and pruning 100% were higher than that in control treatment, implying that M. oleifera might evolve compensatory growth after pruning. The General Linear Models （GLMs） and the Standardized Major Axis Estimation （SMA） had the same determination coefficients, but the allometry coefficients of GLMs were lower than that of SMA （84.9%- 91.9%）. Allometry coefficient increased with the increases of pruning intensity, whereas topping decreased the coefficient. Such a phenomenon indicated that M. oleifera would allocate more resources to vertical growth under pruning, while topping had the opposite impacts. Pruning 50% was recommended for the management of M. oleifera in practice.