Schymanski Stanislaus J, Roderick Michael L, Sivapalan Murugesu, Hutley Lindsay B, Beringer Jason
School of Environmental Systems Engineering, The University of Western Australia, Perth, Australia.
Plant Cell Environ. 2008 Jan;31(1):97-111. doi: 10.1111/j.1365-3040.2007.01740.x. Epub 2007 Oct 30.
Common empirical models of stomatal conductivity often incorporate a sensitivity of stomata to the rate of leaf photosynthesis. Such a sensitivity has been predicted on theoretical terms by Cowan and Farquhar, who postulated that stomata should adjust dynamically to maximize photosynthesis for a given water loss. In this study, we implemented the Cowan and Farquhar hypothesis of optimal stomatal conductivity into a canopy gas exchange model, and predicted the diurnal and daily variability of transpiration for a savanna site in the wet-dry tropics of northern Australia. The predicted transpiration dynamics were then compared with observations at the site using the eddy covariance technique. The observations were also used to evaluate two alternative approaches: constant conductivity and a tuned empirical model. The model based on the optimal water-use hypothesis performed better than the one based on constant stomatal conductivity, and at least as well as the tuned empirical model. This suggests that the optimal water-use hypothesis is useful for modelling canopy gas exchange, and that it can reduce the need for model parameterization.
常见的气孔导度经验模型通常包含气孔对叶片光合作用速率的敏感性。考恩和法夸尔从理论角度预测了这种敏感性，他们假定气孔应动态调整，以便在给定的水分损失情况下使光合作用最大化。在本研究中，我们将考恩和法夸尔的最优气孔导度假说应用于冠层气体交换模型，并预测了澳大利亚北部干湿热带地区一个稀树草原站点的蒸腾作用的日变化和日际变化。然后，使用涡度相关技术将预测的蒸腾动态与该站点的观测结果进行比较。这些观测结果还用于评估两种替代方法：恒定导度和一个经过调整的经验模型。基于最优水分利用假说的模型比基于恒定气孔导度的模型表现更好，并且至少与经过调整的经验模型一样好。这表明最优水分利用假说对于冠层气体交换建模很有用，并且可以减少模型参数化的需求。
