Wood density explains architectural differentiation across 145 co-occurring tropical tree species
Wood density explains architectural differentiation across 145 co-occurring tropical tree species
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DOI：
10.1111/j.1365-2435.2011.01921.x
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发表时间：
2012-02-01
影响因子：
5.2
通讯作者：
Kohyama, Takashi S.
中科院分区：
文献类型：
--
作者：
Iida, Yoshiko;Poorter, Lourens;Kohyama, Takashi S.
1.由于其机械特性，木材密度可能会影响树木以机械稳定的方式扩展茎和树冠以利用有利的光照条件的方式。从工程理论和木材密度特性出发，预测在生物量投资方面，低密度木材对于垂直茎扩展更有效，而高密度木材对于水平分支扩展更有效。到目前为止，这些预测很少经过实证研究的检验。 2. 我们对马来西亚热带雨林中 145 种共生树种的这些预测进行了测试。对于每个物种，我们选择了各种尺寸的树木，并测量了建筑尺寸（茎直径、最低叶子的高度和树冠宽度）。我们使用分层贝叶斯模型来估计建筑尺寸之间的物种特异性异速生长关系，包括估计的茎生物量。然后，我们检查了物种木材密度与标准化高度下的估计建筑变量之间的相关性。 3. 当在标准化树高下比较物种时，在大多数参考高度，木材密度与茎直径呈负相关，与茎生物量呈正相关。这表明木材密度低的物种产生更粗的茎，但生物量成本更低。木材密度与树冠宽度呈正相关，与最低叶子的高度呈负相关，这表明高木材密度物种比低木材密度物种具有更宽和更深的树冠。这些关系在大多数参考高度都保持不变。然而，在18 m高度以上，与冠幅的关系不显着。这可能反映了侧冠扩张对局部条件的大塑性响应。 4. 木材密度解释了共生热带树种的有效垂直茎扩张和水平树冠扩张之间的权衡。这种机械限制体现了低木材密度树种之间树木结构的差异，低木材密度树种表现出有效的高度扩张，以在暴露的树冠中获得更好的光照条件，而高木材密度树种表现出有效的水平树冠扩张，以增强遮荫森林下层当前的光拦截和持久性。因此，我们的研究表明，木材密度设定的机械限制有助于结构和光捕获策略不同的物种的共存。
1.Because of its mechanical properties, wood density may affect the way that trees expand their stem and crown to exploit favourable light conditions in a mechanically stable way. From engineering theory and wood density properties, it is predicted that in terms of biomass investment, low-density wood is more efficient for vertical stem expansion, while high-density wood is more efficient for horizontal branch expansion. So far, these predictions have rarely been tested by empirical studies. 2. We tested these predictions for 145 co-occurring tree species in a Malaysian tropical rainforest. For each species, we selected trees across a broad size range and measured architectural dimensions (stem diameter, height of the lowest foliage and crown width). We used a hierarchical Bayesian model to estimate species-specific allometric relationships between architectural dimensions including estimated stem biomass. Then, we examined correlations between species wood density and estimated architectural variables at standardized heights. 3. When species were compared at standardized tree heights, wood density correlated negatively with stem diameter and positively with stem biomass at most reference heights. This indicates that species with low wood density produce thicker stems but at lower biomass costs. Wood density correlated positively with crown width and negatively with height of the lowest foliage, which indicates that high wood density species have wider and deeper crowns than low wood density species. These relationships were maintained at most reference heights. However, the relationship with crown width was nonsignificant above 18 m height. This may reflect large plastic response of lateral crown expansion to a local condition. 4. Wood density explains the trade-off between effective vertical stem expansion and horizontal crown expansion across co-occurring tropical tree species. Such mechanical constraints characterize the difference in tree architecture between low wood density species that show an efficient height expansion to attain better light conditions in the exposed canopy and high wood density species that show an efficient horizontal crown expansion to enhance current light interception and persistence in the shaded forest understorey. Our study thus suggests that the mechanical constraints set by wood density contribute to the co-existence of species differing in architecture and light capture strategy.