Tree level hydrodynamic approach for resolving aboveground water storage and stomatal conductance and modeling the effects of tree hydraulic strategy
Tree level hydrodynamic approach for resolving aboveground water storage and stomatal conductance and modeling the effects of tree hydraulic strategy
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用于解决地上蓄水和气孔导度并对树木水力策略效果进行建模的树级水动力方法
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发表时间：
2016
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通讯作者：
K. Schäfer
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作者：
G. Mirfenderesgi;G. Bohrer;A. Matheny;S. Fatichi;Renato Prata Moraes Frasson;K. Schäfer
有限差分生态系统尺度树冠水动力模型2 （FETCH2）是一个树木尺度蒸腾水动力模型。FETCH2模型采用有限差分数值方法和简化的单梁管道系统来明确地解析整个树木垂直范围内的木质部水势。经验方程将茎内的水势与整个树冠各高度叶片的气孔导度联系起来。这种方法虽然高度简化，但通过将气孔响应与茎干水势联系起来，而不是像目前大多数陆地表面模型那样直接与土壤湿度联系起来，使蒸腾模拟更加真实。FETCH2决定了气孔各向异性/等水响应程度、最大木质部电导率、叶面积垂直分布、最大和最小木质部含水量等植物水力性状。利用FETCH2数据，结合美国新泽西州Silas Little实验林两属（橡树/松树）混合样地的液流和涡动相关数据，分析了水力策略的属间变化及其对日和季节蒸腾动态的影响。我们通过描述属水平蒸腾和木质部电导率对茎水势变化的响应参数来定义这些策略。结果表明，与传统模式相比，FETCH2显著改善了生态系统蒸腾和潜热通量的模拟。虚拟实验表明，该模型能够捕捉不同土壤水分有效性条件下等水/各向异性等水行为对气孔导度的影响。
The finite difference ecosystem‐scale tree crown hydrodynamics model version 2 (FETCH2) is a tree‐scale hydrodynamic model of transpiration. The FETCH2 model employs a finite difference numerical methodology and a simplified single‐beam conduit system to explicitly resolve xylem water potentials throughout the vertical extent of a tree. Empirical equations relate water potential within the stem to stomatal conductance of the leaves at each height throughout the crown. While highly simplified, this approach brings additional realism to the simulation of transpiration by linking stomatal responses to stem water potential rather than directly to soil moisture, as is currently the case in the majority of land surface models. FETCH2 accounts for plant hydraulic traits, such as the degree of anisohydric/isohydric response of stomata, maximal xylem conductivity, vertical distribution of leaf area, and maximal and minimal xylem water content. We used FETCH2 along with sap flow and eddy covariance data sets collected from a mixed plot of two genera (oak/pine) in Silas Little Experimental Forest, NJ, USA, to conduct an analysis of the intergeneric variation of hydraulic strategies and their effects on diurnal and seasonal transpiration dynamics. We define these strategies through the parameters that describe the genus level transpiration and xylem conductivity responses to changes in stem water potential. Our evaluation revealed that FETCH2 considerably improved the simulation of ecosystem transpiration and latent heat flux in comparison to more conventional models. A virtual experiment showed that the model was able to capture the effect of hydraulic strategies such as isohydric/anisohydric behavior on stomatal conductance under different soil‐water availability conditions.