Self-shading affects allometric scaling in trees
Self-shading affects allometric scaling in trees
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DOI：
10.1111/j.1365-2435.2010.01690.x
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发表时间：
2010-08-01
影响因子：
5.2
通讯作者：
Roberts, Scott D.
中科院分区：
文献类型：
--
作者：
Duursma, Remko A.;Makela, Annikki;Roberts, Scott D.
P>1。West等人[Science，284（1999）1677]在假定资源均匀分布在交换表面之间的情况下导出了最佳的体型标度指数，从而得到了众所周知的3/4标度规则。在树木中，这意味着一个体积填充的分支网络（叶子的分形维数为3）。然而，有证据表明树木的分形维数小于3.在这里，我们包括自着色的最佳分形维数的推导。在自遮光的情况下，资源不会均匀地分布在叶子之间，因为光线从表面进入树冠，并在树冠内逐渐衰减。我们发现，最佳的分形维数可以采取2和3之间的值，这取决于光截获性能和树冠大小.对于一个大的数据集裸子植物的树叶和木质生物量，我们确认，树叶的分形维数小于3，它表现出弱的依赖于冠的大小。然而，树叶生物量与树冠木本生物量的比例指数为0中心点78，非常接近理论预期的3/4比例。这可以解释为树冠木质生物量和树冠长度的比例与理论预测的偏差.总的来说，这些结果证实了裸子植物树的体积填充偏差，我们提供了一个解释这种偏差的最佳代谢缩放。由于3/4缩放的树叶生物量仍然是近似有效的，这意味着代谢缩放指数可能不紧密相连的分形维数的树叶，如先前所假设的。
P>1. West et al. [Science, 284 (1999) 1677] derived an optimal body-size scaling exponent under the assumption that resources are evenly distributed among exchange surfaces, leading to the well-known 3/4 scaling rule. In trees, this implies a volume-filling branching network (a fractal dimension of 3 for foliage). However, there is evidence that the fractal dimension is less than 3 in trees.2. Here, we include self-shading in the derivation of optimal fractal dimensions. With self-shading, resources are not evenly distributed among leaves because light enters the crown at the surface and is gradually attenuated within the crown. We find that the optimal fractal dimension can take values between 2 and 3, depending on light interception properties and crown size.3. For a large data set on foliage and woody biomass in gymnosperm trees, we confirm that the fractal dimension of foliage is less than 3, and that it shows a weak dependence on crown size. However, foliage biomass scaled with crown woody biomass with an exponent of 0 center dot 78, very close to the theoretical expectation of 3/4 scaling. This can be explained by a deviation from the theoretical prediction in the scaling of crown woody biomass and crown length.4. Overall, these results confirm a deviation from volume filling in gymnosperm trees, and we provide an explanation for this deviation in terms of optimal metabolic scaling. Because 3/4 scaling of foliage biomass is still approximately valid, this implies that metabolic scaling exponents may not be as tightly linked to the fractal dimension of foliage as previously assumed.