SGER: Modeling Transpiration and Water-Stress from Leaf-Level to Catchment-Scale: A Supplement for Graduate Study

SGER：从叶级到流域规模的蒸腾和水分胁迫建模：研究生学习的补充

• 批准号: 0727649
• 负责人: Howard Epstein
• 金额: $ 5.01万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0727649&HistoricalAwards=false
• 关键词: SGER; Modeling; Transpiration; Water; Stress

The scientific intent of this research is to develop and demonstrate the applicability of a new, process-based method for evaluating plant water-stress at spatial scales ranging from a single leaf to an entire watershed, and at temporal scales ranging from several minutes to an entire growing season. At the core of the modeling strategy is a formulation of transpiration constructed from two preexisting submodels of stomatal conductance. One model is the 'traditional' Ball et al. [1987] - Farquhar et al. [1980] biophysical model of stomatal conductance coupled to CO2 assimilation (as modified by Leuning [1995]). The second is a mechanistic model of stomatal conductance developed by Gao et al. [2002] that invokes the dynamics of a soil-plant-atmosphere continuum of water. By coupling these two models of stomatal conductance (the first independent of soil water and the second limited by soil water), transpiration may be evaluated in terms of a quantitative and mechanistic dependence upon plant water-stress. Moreover, plant water-stress itself becomes a variable defined in terms of the parameters and other independent variables required by the model; it is therefore also representative of climatic conditions and vegetation status. Scaling these processes across landscapes and seasons will provide insight into the spatial and temporal heterogeneity of plant water-stress and transpiration, and is intended to aid in water-balance closure at the watershed scale. The study site is the Tenderfoot Creek Experimental Forest in Montana, a subcatchment of which (Stringer Creek) is currently the focus of an extensive NSF-funded study of CO2 - H2O relations on a watershed-wide scale. The experimental watershed is covered by a mosaic landscape of conifer forests and meadows, appropriate for examining model sensitivities to parameters representing these diverse functional types of vegetation. The research would characterize transpiration and plant water-stress across the Stringer Creek watershed during the 2006 "water year" (October 2005 through September 2006) with particular emphasis on the 2006 growing season. Leaf-level photosynthesis measurements will be used to estimate submodel parameters for forest and riparian meadow vegetation types. LIDAR measurements obtained during September 2005 and additional IKONOS imagery will be used to scale leaf-level estimates of transpiration to the entire Stringer Creek watershed. Estimates of transpiration will be combined with a Priestly-Taylor approach for estimating evaporation from the soil, yielding a watershed-scale estimate of evapotranspiration that may be validated against both Stringer Creek's water budget and evapotranspiration measured by two eddy covariance systems installed within the watershed during 2005.The broader impacts of this funding will support an excellent graduate student and provide an outstanding opportunity to build on current research involving coupled water and carbon cycling at the watershed scale. The goal is to extrapolate process-based modeling of plant-water relations across a well-studied watershed, and improve methodologies and capabilities for making watershed-scale estimates of land-atmosphere water exchange.

这项研究的科学意图是开发和证明一种基于过程的新方法的适用性，用于评估植物水压力的空间尺度，从单一叶到整个流域，以及从几分钟到整个生长季节不等的时间尺度。建模策略的核心是由两种先前存在的气孔电导的子模型构成的蒸腾表述。一种模型是“传统” Ball等。 [1987] -Farquhar等。 [1980]气孔电导的生物物理模型耦合了CO2同化（如Leuning [1995]修饰）。第二个是Gao等人开发的气孔电导的机械模型。 [2002]调用了土壤植物 - 大气连续水的动力学。通过将这两种模型的气孔电导耦合（第一个独立于土壤水，第二个独立于土壤水），可以根据定量和机械性依赖植物水压力来评估蒸腾作用。此外，根据模型所需的参数和其他独立变量，植物水压力本身成为一个变量。因此，它也代表了气候条件和植被状况。在跨景观和季节中扩展这些过程将提供有关植物水压力和蒸腾作用的空间和时间异质性的洞察力，并旨在帮助在流域量表上闭合水平衡。该研究地点是蒙大拿州的嫩脚溪实验森林，该子捕捉（Stringer Creek）目前是NSF资助的广泛的CO2-H2O关系研究的重点。实验流域被针叶树林和草地的镶嵌景观覆盖，适合检查模型敏感性，以表明代表这些不同功能类型的植被的参数。这项研究将表征2006年“水年”（2005年10月至2006年9月）期间Stringer Creek流域的蒸腾和植物水压力，特别着重于2006年的生长季节。叶片水平的光合作用测量将用于估计森林和河岸草甸植被类型的子模型参数。 2005年9月获得的激光雷达测量值，并将使用其他Ikonos图像来缩放叶片水平的蒸腾估计值，以缩小整个Stringer Creek流域。蒸腾的估计值将与祭司泰勒的方法相结合，用于估算土壤蒸发，得出蒸发的分水岭估计估计，可以通过在急流中衡量的两种既定的启动式的逐步启动，可以通过在2005年的范围内进行逐步建立，以验证两位界限的启动。在流域量表上涉及水和碳循环的研究。目的是推断基于过程的植物 - 水关系建模，跨流域，并改善了对土地 - 大气水交换的分水岭估计的方法和能力。