Abstract Differences in growth rates between Eucalyptus clones depend on differences in the acquisition of resources, and the efficiency of using resources to produce carbohydrates and grow wood. We examined differences in canopy structure, light interception, and light use efficiency for the 18 TECHS clones in a common garden experiment in Brazil. The degree of clumping within canopies varied substantially among clones, leading to large differences in both leaf area and light interception per unit of leaf area. Two methods of determining plot-level leaf area index (LP-80 and LAI-2000) were moderately well correlated ( R 2 = 0.4), but both methods underestimated actual leaf area index (determined by destructive sampling) by about one-third. Completely overcast sky conditions increased accuracy of leaf area estimates, reducing variation among measurements within plots and lowering the number of samples needed to obtain a given level of precision. Genotypes with high leaf area clumping also had higher leaf angle inclinations than genotypes with lower clumping. The apparent light interception coefficient ( k ) averaged 0.56 for the LP-80, and 0.47 for the LAI-2000. The range of k estimates differed by up to 2-fold among clones, underscoring the limited generality of light extinction coefficients. Light interception ranged from about 70 to 95% of incoming light, and leaf area index accounted for only 30% of the pattern in light interception among clones. Differences in stemwood production were influenced more strongly by clonal differences in efficiency of light use (stemwood production per unit of light intercepted) than by differences in leaf area or light interception. The efficiency of producing wood per unit of light intercepted spanned a two-fold range, with higher efficiencies for more productive clones. We suggest that production ecology studies focus more on measurements of light interception than on leaf area, avoiding issues about difficult-to-measure features of crown and canopy structures. The additional step of characterizing light use efficiency would also be very important.

中文翻译：

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桉树无性系冠层结构、叶面积、光截留和光利用效率的变化

摘要 桉树无性系之间生长速度的差异取决于资源获取的差异，以及利用资源生产碳水化合物和种植木材的效率。我们在巴西的一个普通花园实验中检查了 18 个 TECHS 克隆在冠层结构、光拦截和光利用效率方面的差异。无性系之间冠层内的结块程度差异很大，导致叶面积和每单位叶面积的光截获量存在很大差异。确定地块级叶面积指数的两种方法（LP-80 和 LAI-2000）具有中等程度的相关性（R 2 = 0.4），但两种方法都低估了实际叶面积指数（通过破坏性采样确定）约三分之一。完全阴天的天空条件提高了叶面积估计的准确性，减少地块内测量值之间的差异，并减少获得给定精度水平所需的样本数量。高叶面积丛的基因型也比低丛的基因型具有更高的叶角倾角。LP-80 的视光拦截系数 (k) 平均为 0.56，LAI-2000 为 0.47。克隆之间 k 估计值的范围差异高达 2 倍，强调了消光系数有限的普遍性。光拦截范围为入射光的 70% 至 95%，叶面积指数仅占克隆间光拦截模式的 30%。与叶面积或光拦截的差异相比，光利用效率的克隆差异（每单位截取光的茎木产量）对茎材产量的影响更大。每单位截获的光产生木材的效率跨越了两倍的范围，对于更高效的克隆具有更高的效率。我们建议生产生态学研究更多地关注光拦截的测量而不是叶面积，避免难以测量的冠和冠结构特征的问题。表征光利用效率的附加步骤也非常重要。我们建议生产生态学研究更多地关注光拦截的测量而不是叶面积，避免难以测量的冠和冠层结构特征的问题。表征光利用效率的附加步骤也非常重要。我们建议生产生态学研究更多地关注光拦截的测量而不是叶面积，避免难以测量的冠和冠结构特征的问题。表征光利用效率的附加步骤也非常重要。