Vessel tapering is conserved along a precipitation gradient in tropical trees of the genus Cedrela
Vessel tapering is conserved along a precipitation gradient in tropical trees of the genus Cedrela
复制标题
DOI：
10.1007/s00468-022-02345-6
复制
发表时间：
2022-10
期刊：
影响因子：
--
通讯作者：
Alexander Chambers-Ostler;E. Gloor;D. Galbraith;P. Groenendijk;Roel Brienen
中科院分区：
文献类型：
--
作者：
Alexander Chambers-Ostler;E. Gloor;D. Galbraith;P. Groenendijk;Roel Brienen
在热带树木的降水梯度中，导管变细的速率是高度保守的，指出树高的极限由最大基部导管直径决定。热带树木的最大高度随着降水量的减少而强烈降低。水力结构在控制这种树高变化中的作用尚不清楚。树木木质部导管从顶端到基部的变宽，也称为变细，对于保持沿着树干的导水率是重要的。相反，如果血管直径恒定，则阻力将随着路径长度的增加而增加，从而随着树高度的增加而限制流速。虽然以前的研究表明，血管直径尺度与树高在一个类似的速度（类似的幂律指数）在整个生物群系和类群，知识在一个单一的物种，尤其是在热带地区的降水梯度的这些关系是不完整的。在这里，我们报告如何导管密度和直径在树的基础上不同的两个tropicalCedrelaspecies在四个网站不同的降水量从1014至2585毫米年-1。我们发现，最大树高随着降水量的减少而减少，从42米到13米。尽管最大树高和水的可用性网站之间的强烈差异，锥形确实是显着的保守和接近出版的缩放高度的基础上多物种分析。因此，对于一个给定的树高，基管直径在不同地点之间没有变化，而最大基管尺寸在干燥的地点（最短的树）比最潮湿的地点（最高的树）小两倍。这表明，考虑到栓塞风险随着干燥程度的增加而增加，树高可能受到最大基底血管直径的限制。我们的研究结果表明，在这个湿度梯度没有水力适应，并揭示了最大树高和最大基底血管大小之间的明确关系。
Key messageThe rate of vessel tapering is highly conserved across a precipitation gradient in tropical trees, pointing to a limit on tree height determined by a maximum basal vessel diameter.Maximum tree height in the tropics decreases strongly with decreasing precipitation. The role of hydraulic architecture in controlling this variation in tree height remains unclear. The widening of conducting xylem vessels from the apex to the base of trees, also known as tapering, is important for maintaining the hydraulic conductivity along the tree stem. If in contrast vessel diameter were constant, then resistance would increase with path length constraining flow rates as tree height increases. Whilst previous research has shown that vessel diameter scales with tree height at a similar rate (similar power law exponent) across biomes and taxa, knowledge on these relationships across precipitation gradients within a single species is incomplete, especially for the tropics. Here we report how vessel density and diameter at the tree base differ for two tropicalCedrelaspecies across four sites varying in precipitation from 1014 to 2585 mm year−1. We find that maximum tree height decreases with decreasing precipitation across sites from 42 to 13 m. Despite the strong differences between sites in maximum tree height and water availability, tapering is indeed remarkably conserved and close to published scaling with height based on multi-species analyses. Thus, for a given tree height, basal vessel diameter does not vary between sites, whilst the maximum basal vessel size is two times smaller at the drier site (with the shortest trees) compared to the wettest site (with the tallest trees). This suggests a possible limitation of tree height determined by a maximum basal vessel diameter that can be sustained, given increasing embolism risk with increasing dryness. Our results show no hydraulic adaptation across this wetness gradient and reveal a clear relationship between maximum tree height and maximum basal vessel size.