Empirical and optimal stomatal controls on leaf and ecosystem level CO2 and H2O exchange rates
Empirical and optimal stomatal controls on leaf and ecosystem level CO2 and H2O exchange rates
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DOI：
10.1016/j.agrformet.2011.07.001
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发表时间：
2011-12-15
影响因子：
6.2
通讯作者：
Hari, Pertti
中科院分区：
文献类型：
--
作者：
Launiainen, Samuli;Katul, Gabriel G.;Hari, Pertti
叶片水平气孔导度（g（s））对环境刺激的响应与冠层水平物质交换过程之间的联系仍然是一个重要的研究问题。探讨了不同g（s）公式如何影响冠层尺度CO2和H2O的平均标量浓度和通量分布，以及如何从叶层参数出发推导代表生态系统质量交换率的大叶的“有效”属性。四个广泛使用的配方为叶级g（s）相结合的叶级光合需求函数，层分辨光衰减模型，和湍流封闭方案的冠层空气空间内的标量通量。四个g（s）模型是广泛使用的半经验Ball-Berry方法，及其修改，以及自主叶片气孔优化理论的两种解决方案。优化理论的两种解决方案之一是基于线性化的CO2需求函数，而另一种则没有调用这种简化。四个气孔控制模型，然后对相同的拍摄规模的气体交换数据收集在位于芬兰南部Hyytiala的SMEAR II站的苏格兰松林参数化。预测的CO2（F-C）和H2O通量（F-E）和平均浓度分布进行了比较，对多层次的涡动协方差测量和平均标量浓度数据内和冠层以上。结果表明，F-c比较的一致性在10%以内，F-e比较的一致性在25%以内。最优的方法来自一个线性化的光合需求函数预测最大的CO2吸收和蒸腾速率相比，涡度协方差测量和其他三个模型。此外，在每个g（s）模型，CO2通量不敏感togs模型参数的变化，而蒸腾速率估计显着更受影响。对每个g（s）模型得出的层平均结果进行垂直积分。对涡动协方差导出的冠层电导对应的放大体积冠层电导的灵敏度进行了比较。结果表明，冠层g（s）比冠层g（s）对水汽压亏缺更为敏感。(C)2011爱思唯尔有限公司版权所有。
Linkage between the leaf-level stomatal conductance (g(s)) response to environmental stimuli and canopy-level mass exchange processes remains an important research problem to be confronted. How various formulations of g(s) influence canopy-scale mean scalar concentration and flux profiles of CO2 and H2O within the canopy and how to derive 'effective' properties of a 'big-leaf that represents the eco-system mass exchange rates starting from leaf-level parameters were explored. Four widely used formulations for leaf-level g(s) were combined with a leaf-level photosynthetic demand function, a layer-resolving light attenuation model, and a turbulent closure scheme for scalar fluxes within the canopy air space. The four g(s) models were the widely used semi-empirical Ball-Berry approach, and its modification, and two solutions to the stomatal optimization theory for autonomous leaves. One of the two solutions to the optimization theory is based on a linearized CO2-demand function while the other does not invoke such simplification. The four stomatal control models were then parameterized against the same shoot-scale gas exchange data collected in a Scots pine forest located at the SMEAR II-station in Hyytiala, Southern Finland. The predicted CO2 (F-c) and H2O fluxes (F-e) and mean concentration profiles were compared against multi-level eddy-covariance measurements and mean scalar concentration data within and above the canopy. It was shown that F-c comparisons agreed to within 10% and F-e comparisons to within 25%. The optimality approach derived from a linearized photosynthetic demand function predicted the largest CO2 uptake and transpiration rates when compared to eddy-covariance measurements and the other three models. Moreover, within each g(s) model, the CO2 fluxes were insensitive togs model parameter variability whereas the transpiration rate estimates were notably more affected. Vertical integration of the layer-averaged results as derived from each g(s) model was carried out. The sensitivities of the up-scaled bulk canopy conductances were compared against the eddy-covariance derived canopy conductance counterpart. It was shown that canopy level g(s) appear more sensitive to vapor-pressure deficit than shoot-level g(s). (C) 2011 Elsevier B.V. All rights reserved.