King David
Department of Botany, University of Wisconsin, 53706, Madison, WI, USA.
Oecologia. 1981 Jan;51(3):351-356. doi: 10.1007/BF00540905.
To determine the effect of tree dimensions on the rate of height growth a model was constructed relating tree weight to total height and R, the ratio of crown weight to trunk weight. The model is based on the assumption that the trunk buckling safety factor is constant. If trees also maintain a constant R as they grow then the rate of height growth is maximized by R=0.17. In addition, the height growth rate increases as the buckling safety factor decreases. These predictions of optimal form for height growth are appropriate for shade intolerant, successional species growing in dense stands. Dimensional measurements of self thinning Populus tremuloides indicate near optimal dimensions for height growth. Trees ranging from 7 to 19 m in height had trunks which were only 50% thicker than the minimum required to prevent them from buckling under their own weight, and had a mean R of 0.13. This ratio of crown weight to trunk weight is significantly lower than the optimal value, but the predicted height growth rate for R=0.13 is 99% of that predicted for R=0.17.
为了确定树木尺寸对树高生长速率的影响，构建了一个模型，该模型将树木重量与总高度以及树冠重量与树干重量之比R联系起来。该模型基于树干屈曲安全系数恒定的假设。如果树木在生长过程中也保持恒定的R值，那么当R = 0.17时，树高生长速率达到最大值。此外，随着屈曲安全系数的降低，树高生长速率会增加。这些关于树高生长最优形态的预测适用于在茂密林分中生长的耐阴、演替物种。对自然稀疏的颤杨进行的尺寸测量表明，其树高生长的尺寸接近最优。高度在7至19米之间的树木，其树干仅比防止自身重量导致屈曲所需的最小厚度厚50%，平均R值为0.13。这种树冠重量与树干重量之比明显低于最优值，但R = 0.13时预测的树高生长速率是R = 0.17时预测值的99%。
