CSIRO Sustainable Ecosystems, Centre for Environment and Life Sciences, Private Bag 5, Wembley, Western Australia 6913, Australia.
Tree Physiol. 2009 Nov;29(11):1407-18. doi: 10.1093/treephys/tpp076. Epub 2009 Sep 28.
Information on how vegetation adapts to differences in water supply is critical for predicting vegetation survival, growth and water use, which, in turn, has important impacts on site hydrology. Many field studies assess adaptation to water stress by comparing between disparate sites, which makes it difficult to distinguish between physiological or morphological changes and long-term genetic adaptation. When planting trees into new environments, the phenotypic adaptations of a species to water stress will be of primary interest. This study examined the response to water availability of Eucalyptus kochii ssp. borealis (C. Gardner) D. Nicolle, commonly integrated with agriculture in south-western Australia for environmental and economic benefits. By choosing a site where the groundwater depth varied but where climate and soil type were the same, we were able to isolate tree response to water supply. Tree growth, leaf area and stand water use were much larger for trees over shallow groundwater than for trees over a deep water table below a silcrete hardpan. However, water use on a leaf area basis was similar in trees over deep and shallow groundwater, as were the minimum leaf water potential observed over different seasons and the turgor loss point. We conclude that homeostasis in leaf water use and water relations was maintained through a combination of stomatal control and adjustment of sapwood-to-leaf area ratios (Huber value). Differences in the Huber value with groundwater depth were associated with different sapwood-specific conductivity and water use on a sapwood area basis. Knowledge of the coordination between water supply, leaf area, sapwood area and leaf transpiration rate for different species will be important when predicting stand water use.
植被如何适应供水差异的信息对于预测植被的生存、生长和水分利用至关重要，而这反过来又对场地水文有重要影响。许多野外研究通过比较不同地点来评估对水分胁迫的适应，这使得很难区分生理或形态变化和长期遗传适应。当将树木种植到新环境中时，物种对水分胁迫的表型适应将是主要关注点。本研究考察了澳大利亚西南部普遍与农业结合以实现环境和经济效益的北澳斑克松（Eucalyptus kochii ssp. borealis (C. Gardner) D. Nicolle）对水分供应的响应。通过选择一个地下水深度不同但气候和土壤类型相同的地点，我们能够将树木对供水的响应与其他因素隔离开来。在浅层地下水上方生长的树木的生长、叶面积和林分水分利用量明显大于在深地下水水位下方的硬磐上生长的树木。然而，基于叶面积的水分利用在深地下水和浅地下水上方的树木中相似，不同季节观察到的最小叶片水势和膨压损失点也相似。我们得出结论，通过气孔控制和调整边材与叶面积比（Huber 值）的组合，维持了叶片水分利用和水分关系的内稳态。Huber 值与地下水深度的差异与不同的边材比导水率和基于边材面积的水分利用有关。当预测林分水分利用时，了解不同物种之间供水、叶面积、边材面积和叶片蒸腾速率之间的协调关系将非常重要。
