Ecohydrological responses of dense canopies to environmental variability: 1. Interplay between vertical structure and photosynthetic pathway
Ecohydrological responses of dense canopies to environmental variability: 1. Interplay between vertical structure and photosynthetic pathway
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茂密冠层对环境变化的生态水文响应：1.垂直结构与光合途径之间的相互作用
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发表时间：
2010
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通讯作者：
M. Sivapalan
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作者：
D. Drewry;Praveen Kumar;S. Long;C. Bernacchi;Xin‐Zhong Liang;M. Sivapalan
[1] 据观察，植被对气候变化的适应，特别是大气中二氧化碳 (CO2) 浓度的升高，包括叶子的生化和生态生理功能以及冠层结构成分的改变。这些反应有可能显着改变植物碳吸收和表面能量分配，并归因于近几十年来表面水文的大规模变化。虽然植被适应的综合效应可能很明显，但它们通常是由冠层特性的微妙变化引起的，需要通过冠层解析物理、生化和生态生理过程才能进行准确估计。本文是两篇论文中的第一篇，提出了一个多层冠层-土壤-根系统模型，旨在捕捉植被对环境变化的新兴响应。该模型结合了 C3 和 C4 光合作用途径，并解决了冠层内的垂直辐射、热和环境状况。叶片生态生理功能和能量平衡之间的紧密耦合决定了植被对气候状态和扰动的响应，而这些响应通过根系深度受到土壤湿度状态的调节。使用在 Bondville（伊利诺伊州）Ameriflux 塔现场收集的 CO2、潜热和显热的涡流协方差通量，对该模型在大豆 (C3) 和玉米 (C4) 的三个生长季节进行了验证。该数据集提供了一个机会来检查重要环境驱动因素和模型技能在捕获冠层-大气交换变化方面的作用。检查平均昼夜周期内辐射状态和标量通量的垂直变化，以了解冠层结构对吸收辐射和标量通量大小的模式的作用，以及通过冠层的阳光照射和阴影源/汇位置的后续差异。分析了土壤水分胁迫对冠层尺度碳吸收和能量通量分配的影响，并通过冠层解决，深入了解冠层结构和代谢途径对每种作物对水分亏缺的响应的作用。模型计算表明，水分利用效率 (WUE) 随着水分胁迫的增加而增加，在本文研究的最高植物胁迫水平下，玉米平均 WUE 增加了 45%，而大豆则增加了 20%。
[1] Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and ecophysiological functioning of leaves and the structural components of the canopy. These responses have the potential to significantly modify plant carbon uptake and surface energy partitioning, and have been attributed with large-scale changes in surface hydrology over recent decades. While the aggregated effects of vegetation acclimation can be pronounced, they often result from subtle changes in canopy properties that require the resolution of physical, biochemical and ecophysiological processes through the canopy for accurate estimation. In this paper, the first of two, a multilayer canopy-soil-root system model developed to capture the emergent vegetation responses to environmental change is presented. The model incorporates both C3 and C4 photosynthetic pathways, and resolves the vertical radiation, thermal, and environmental regimes within the canopy. The tight coupling between leaf ecophysiological functioning and energy balance determines vegetation responses to climate states and perturbations, which are modulated by soil moisture states through the depth of the root system. The model is validated for three growing seasons each for soybean (C3) and maize (C4) using eddy-covariance fluxes of CO2, latent, and sensible heat collected at the Bondville (Illinois) Ameriflux tower site. The data set provides an opportunity to examine the role of important environmental drivers and model skill in capturing variability in canopy-atmosphere exchange. Vertical variation in radiative states and scalar fluxes over a mean diurnal cycle are examined to understand the role of canopy structure on the patterns of absorbed radiation and scalar flux magnitudes and the consequent differences in sunlit and shaded source/sink locations through the canopies. An analysis is made of the impact of soil moisture stress on carbon uptake and energy flux partitioning at the canopy-scale and resolved through the canopy, providing insight into the roles of canopy structure and metabolic pathway on the response of each crop to moisture deficits. Model calculations indicate increases in water use efficiency (WUE) with increasing moisture stress, with average maize WUE increases of 45% at the highest levels of plant stress examined here, relative to 20% increases for soybean.