Collaborative Research: Restricted Plasticity of Canopy Stomatal Conductance: A Conceptual Basis for Simpler Spatial Models of Forest Transpiration

从与美国全球变化研究项目有关的水和碳小组最近的报告中可以清楚地看出，森林系统中冠层气孔导度的准确预测对于理解陆地表面-大气通量及其如何受到气候和土地利用变化的影响至关重要。事实上，土地利用的变化正在产生更破碎的景观，而这些在目前的陆地表面模型中不容易表现出来。目前的森林通量模型是在这样的研究范式下建立的：确定均匀的森林林分，在这些林分的中心进行通量测量，然后将这里的研究结果外推到整个林分及更远的地方。考虑到植物群落的空间复杂性，这种方法既没有必要也不合理。该项目旨在建立一个森林蒸腾的概念模型，该模型包含气孔控制的固有空间变异性，同时保留一个易于处理的概括性测量，这是气孔导度经验模型的标志。我们的概念模型基于这样一种观点，即当水通量高且具有重要的水文意义时，冠层气孔导度主要由水势调节。本文认为，冠层气孔导度的物种可塑性决定了其空间变异性和量化的挑战。从最近与美国全球变化研究计划有关的水和碳小组的报告中可以清楚地看出，森林系统中冠层气孔导度的准确预测对于理解陆地表面-大气通量及其如何受到气候和土地利用变化的影响至关重要。事实上，土地利用的变化正在产生更破碎的景观，而这些在目前的陆地表面模型中不容易表现出来。目前的森林通量模型是在这样的研究范式下建立的：确定均匀的森林林分，在这些林分的中心进行通量测量，然后将这里的研究结果外推到整个林分及更远的地方。考虑到植物群落的空间复杂性，这种方法既没有必要也不合理。该项目旨在建立一个森林蒸腾的概念模型，该模型包含气孔控制的固有空间变异性，同时保留一个易于处理的概括性测量，这是气孔导度经验模型的标志。我们的概念模型基于这样一种观点，即当水通量高且具有重要的水文意义时，冠层气孔导度主要由水势调节。我们认为，物种在冠层气孔导度中的可塑性，决定了其空间变异性和量化的挑战，遵循一个线性关系，这与一个容易量化的参考导度是分离的。

0405318KrugerIt is clear from recent reports by the water and carbon groups associated with the United States Global Change Research Program that accurate predictions of canopy stomatal conductance in forested systems are critical for the understanding of land surface - atmosphere fluxes and how they are affected by climate and land use changes. Indeed, land use changes are producing more fragmented landscapes and these are not readily represented in current land surface models. Current forest flux models were developed under the paradigm of research in which uniform forest stands are identified, flux measurements are made in the centers of these stands, and then what is learned here is extrapolated to the entire stand and beyond. This approach is neither necessary nor justified given the spatial complexity of vegetative communities. This projectseeks to develop a conceptual model of forest transpiration that embraces the inherent spatial variability of stomatal control while retaining a tractable measure of generalizability that is the hallmark of empirical models of stomatal conductance. Our conceptual model is based on the idea that canopy stomatal conductance is regulated primarily by water potential when water fluxes are high and of significant hydrologic import. We propose that species plasticity in canopy stomatal conductance, which determines its spatial variability and challenge for quantifying, follows a linear relationship that is keyed off of an easily quantifiable reference conductance0405318KrugerIt is clear from recent reports by the water and carbon groups associated with the United States Global Change Research Program that accurate predictions of canopy stomatal conductance in forested systems are critical for the understanding of land surface - atmosphere fluxes and how they are affected by climate and land use changes. Indeed, land use changes are producing more fragmented landscapes and these are not readily represented in current land surface models. Current forest flux models were developed under the paradigm of research in which uniform forest stands are identified, flux measurements are made in the centers of these stands, and then what is learned here is extrapolated to the entire stand and beyond. This approach is neither necessary nor justified given the spatial complexity of vegetative communities. This projectseeks to develop a conceptual model of forest transpiration that embraces the inherent spatial variability of stomatal control while retaining a tractable measure of generalizability that is the hallmark of empirical models of stomatal conductance. Our conceptual model is based on the idea that canopy stomatal conductance is regulated primarily by water potential when water fluxes are high and of significant hydrologic import. We propose that species plasticity in canopy stomatal conductance, which determines its spatial variability and challenge for quantifying, follows a linear relationship that is keyed off of an easily quantifiable reference conductance.