NSF Young Investigator

道森森林覆盖了37%的陆地表面。构成这些森林的树木是水重新进入水文循环的主要途径。NSF青年研究员（NYI）奖的目标是了解和评估树木和森林在当地和区域水文过程中的重要性。这将通过一项有四个具体目标的调查来完成：(1)利用O和H稳定同位素方法、涡动相关和空气动力能量平衡技术以及Bowen-ratio方法描述孤立树木和林分的水分平衡；(2)利用叶片、冠层和林分水平的蒸腾估算和同位素技术表征树木控制林分运动和水分流失的程度；运动和损失响应（调整）模拟气候变化的实验操作（例如，灌溉树木，防止蒸腾），以及(4)整合从观测/描述性研究（目标1和2）、实验研究（目标3）以及从个体和整个林分收集的信息，形成树木和森林在全球水运动中所起作用的综合图景。由于总体目标是完善我们对树木和森林在水文循环中的重要性和作用的理解，因此有必要使用多种研究方法。所选择的方法组合将提供一种验证信息、整合不同层次和校准预测的手段。稳定同位素和涡流相关方法是最有效的方法。对水源水、植物木质液和大气水汽水样的稳定同位素组成分析已成功地用于评估土壤-植物-大气连续体中的水通量。涡旋相关技术是一种有效的方法来量化水通过植物树冠和林分的运动。基于Penman-Monteith方程的水通量气动能量平衡方法和Bowen-ratio法（感/潜热通量）可以提供独立校验同位素和涡动相关结果的方法。从这些研究中获得的信息将帮助我们了解气候和气候变化可能对世界森林地区的功能和结构特征产生的影响，完善我们对植被表面在水文循环和局部和区域水平衡中所起作用的经验认识，并在大气和植物生物学研究之间建立急需的联系。＊＊＊

9357274 Dawson Forests cover 37% of all terrestrial surfaces. The trees that compose these forests are a primary route by which water re-enters the hydrologic cycle. The objectives of this NSF Young Investigator (NYI) Award are to understand and evaluate the importance that trees and forests play in local and regional hydroglogic processes. This will be accomplished through an investigation that has four specific goals: (1) describe the water balance of isolated trees and of forests stands using O and H stable isotope methods, eddy correlation and aerodynamic-energy balance techniques, and the Bowen-ratio method, (2) characterize the degree to which trees control movement and loss of water from forest stands with leaf-, canopy- and stand-level transpiration estimates and isotope techniques, (3) investigate how water uptake, movement and loss respond (adjust) to experimental manipulation mimicking climate change (e.g. irrigating trees, preventing transpiration), and (4) integrate the information gathered from the observational/descriptive studies (objectives 1 and 2), the experimental studies (objective 3), and from both individuals and entire stands into a comprehensive picture of the role that trees and forests play in global water movement. Because the overall objective is to refine our understanding of the importance and role that trees and forests play in the hydrologic cycle, it is necessary to use a variety of research methods. The combination of methods chosen will provide a means to validate information, integrate different levels, and calibrate predictions. The stable isotope and eddy correlation methods are the most powerful. An analysis of the stable isotopic composition of water samples obtained from source water, plant xylem-sap, and atmospheric water vapor has been successfully used to evaluate water flux through the soil-plant-atmospheric continuum. The eddy correlation technique is a powerful way to quantify water movement through pla nt canopies and stands. Aerodynamic-energy balance methods of water flux based on the Penman-Monteith equation, and the Bowen-ratio method (sensible/latent heat flux) can provide ways to independently check the isotope and eddy correlation results. The information obtained from these studies will help us understand the impacts that climate and climate change may have on the functional and structural characteristics of forested regions of the world, refine our empirical understanding of the role that vegetated surfaces play in the hydrologic cycle and local and regional water balance, and to forge a much-needed link between atmospheric and plant biological research. ***