Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems
Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems
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DOI：
10.1007/s00442-007-0918-5
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发表时间：
2008-03-01
期刊：
影响因子：
2.7
通讯作者：
Goldstein, Guillermo
中科院分区：
文献类型：
--
作者：
Hao, Guang-You;Hoffmann, William A.;Goldstein, Guillermo
研究了6对由一种典型稀树草原生境树种和另一种典型邻近森林生境树种组成的同属物种对与植物水分关系相关的叶和茎功能性状，以确定这两种功能类型之间的植物水力学是否存在内在差异。只研究了生长在稀树草原栖息地的个体。大部分茎秆性状，包括木材密度、木质部水势、边材面积比电导率和叶面积比电导率在热带稀树草原和森林树种之间没有显著差异。而最大叶片水力导度（K-leaf）和叶片电容在热带稀树草原物种中有较高的趋势。在所有同属对中，热带稀树草原物种的黎明前叶水势和单位面积叶质量也较高。茎叶的水力易损性曲线表明，无论属还是属，叶片都比顶枝更容易受到干旱引起的空化。根据叶片易损性曲线估计的正午k叶值非常低，表明叶片可能发生每日栓塞修复。电路模拟模型预测，与森林物种相比，热带稀树草原物种的叶片水势从黎明前的值下降到k叶损失50%或膨胀损失点所需的时间更长，这表明热带稀树草原物种对叶片水势的变化有更大的缓冲作用。本研究的结果表明，热带稀树草原相对于森林物种在热带稀树草原上的相对成功部分与它们应对干旱的能力有关，这更多地取决于叶片而不是茎的水力特性。在大多数性状中，属间变异占总变异的很大比例，这表明尽管在热带稀树草原和森林生境中存在不同的选择压力，但系统发育在决定大多数水力性状方面的作用强于生境。
Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats were studied. Most stem traits, including wood density, the xylem water potential at 50% loss of hydraulic conductivity, sapwood area specific conductivity, and leaf area specific conductivity did not differ significantly between savanna and forest species. However, maximum leaf hydraulic conductance (K-leaf) and leaf capacitance tended to be higher in savanna species. Predawn leaf water potential and leaf mass per area were also higher in savanna species in all congeneric pairs. Hydraulic vulnerability curves of stems and leaves indicated that leaves were more vulnerable to drought-induced cavitation than terminal branches regardless of genus. The midday K-leaf values estimated from leaf vulnerability curves were very low implying that daily embolism repair may occur in leaves. An electric circuit analog model predicted that, compared to forest species, savanna species took longer for their leaf water potentials to drop from predawn values to values corresponding to 50% loss of K-leaf or to the turgor loss points, suggesting that savanna species were more buffered from changes in leaf water potential. The results of this study suggest that the relative success of savanna over forest species in savanna is related in part to their ability to cope with drought, which is determined more by leaf than by stem hydraulic traits. Variation among genera accounted for a large proportion of the total variance in most traits, which indicates that, despite different selective pressures in savanna and forest habitats, phylogeny has a stronger effect than habitat in determining most hydraulic traits.