RUI: Measurement and modeling of rainfall interception loss from Georgia Southern University's urban forest.

森林冠层可以通过拦截、储存和蒸发树叶和树皮表面的液滴，使到达地面的降水减少50%。这个过程被称为“截流损失”，影响径流、补给、洪水暴发、侵蚀等，以及雨水管理的成本。目前还不清楚冠层结构如何影响截流损失，特别是在城市森林中。本研究通过监测一种常见的东南美洲树种（火炬松）在森林结构中从自然到城市的梯度上的拦截损失变量来解决这一问题。监测的截流损失变量包括雨冠中储存和蒸发的雨水、穿过雨冠的雨水（throughfall）、沿茎排下的雨水（stemflow），以及雨中和雨后的空气温度、湿度、风速/风向、压力和入射太阳辐射。这些测量将与新的、高分辨率、非破坏性激光扫描（LiDAR）技术相关，以解决两个问题：1)从自然条件到普通城市条件的森林结构变化如何影响拦截损失过程；2)激光雷达测量的冠层结构和截流损失过程是否能改善水文过程的估计和预测，从而改善水资源管理和规划？假设是，由于树木的立地条件会影响树枝和叶子的结构，拦截损失及其潜在的变量会随着风暴条件的变化而变化。将这些反应纳入共同模型将对有关风暴条件变化的水管理具有预测价值。这是一个芮（本科院校研究）项目，将培养本科生的前沿水文科学，并将其纳入教育推广工作，惠及数千名K-12学生、本科生、高中教师和社区成员。佐治亚南方大学（GSU）有大量的非裔美国学生（2012年和2013年分别占本科生的25.7%和26.4%），因此该项目将为代表性不足的群体提供研究经验。项目数据将用于开发GSU校园的管理实践。森林冠层降雨拦截损失(I)对径流、补给、洪水暴发、侵蚀和雨水管理基础设施的成本产生重大影响。然而，森林冠层结构如何控制I的组成部分（储水量S和蒸发量E），特别是在城市森林中，还不是很清楚。目前还没有研究：1)比较不同冠层结构的自然-城市森林连续体的S和E行为，或2)将陆地激光雷达（TLiDAR）测量的冠层结构及其与S和E动力学的相互作用纳入常见的I模型。这项研究将沿着乔治亚南部大学（GSU）校园的自然到城市森林结构梯度进行，使用区域优势物种（油松，火炬松）。该研究将现有的生物气象监测方法（气象、茎流和穿透测量）与新型地面激光雷达技术（LaserBark和L-Architect）结合起来，将城市森林中的S和E与直接、非破坏性测量的冠层结构指标进行比较。这解决了两个问题：1)2个城市森林结构的S和E的风暴间和风暴内动态如何变化，与自然林分相比如何；2)城市林分中直接测量的冠层结构在多大程度上可以改变最常用模型（即Gash-和rutter -类型）的输出、参数甚至参数化？这些发现将推动几乎所有模拟或包括森林截流过程的水文模型。六名本科生将获得丰富的研究经验，涵盖水资源管理这一及时而关键的子领域的研究活动（包括现场仪器培训、安装和维护；数据收集和处理；建模和模型评估；手稿准备；以及在国家会议上的演讲）。数据还将用于改进：1)L-Architect模型，该模型正被纳入Computree，这是国家统计局Forêts（法国）用于全国改进森林清单的工具；2)目前在GSU校园采用的可持续灌溉方法。

Forest canopy can reduce precipitation reaching the ground by up to 50% through interception, storage, and evaporation of droplets from leaf and bark surfaces. This process, called "interception loss," impacts run-off, recharge, flood flashiness, erosion, etc., and cost of stormwater management. It is not well understood how canopy structure affects interception loss, particularly in urban forests. This research addresses this by monitoring interception loss variables for a common SE US tree species (the loblolly pine) across a natural-to-urban gradient in forest structure. Interception loss variables monitored include rainwater stored in and evaporated from the canopy, passing through the canopy (throughfall), and draining down the stem (stemflow) as well as air temperature, humidity, wind speed/direction, pressure, and incoming solar radiation during and after rainfall. These measurements will be related to new, high-resolution, non-destructive laser-scanning (LiDAR) techniques to address 2 questions: 1) how do stand structural changes ranging from natural conditions to common urban conditions affect interception loss processes; and 2) Will LiDAR-measured canopy structures and interception loss processes improve estimation and prediction of hydrologic processes and, thereby, improve water management and planning? The hypothesis is that, because tree stand conditions affect branching and leaf structures, interception loss and its underlying variables will vary in response to storm conditions. Inclusion of these responses in common models will have predictive value for water management concerning shifts in storm conditions . This is an RUI (Research at Undergraduate Institutions) project that will train undergraduate students in cutting-edge hydrologic science and be incorporated into educational outreach efforts reaching thousands of K-12 students, undergraduate students, high school teachers, and community members. Georgia Southern University (GSU) has a substantial African American student population (25.7% and 26.4% of undergraduates in 2012 and 2013), so the project will provide research experiences to underrepresented groups. Project data will be used to develop management practices on the GSU campus. Forest canopy rainfall interception loss (I) is documented to exert significant influence on run-off, recharge, flood flashiness, erosion and the cost of stormwater management infrastructure. However, it is not well understood how the forest canopy structure controls the components of I (storage, S, and evaporation, E), particularly in urban forests. No existing study has: 1) compared S and E behavior along a natural-urban forest continuum of differing canopy architecture or 2) incorporated terrestrial LiDAR (TLiDAR) measured canopy structures and the interaction of these structures with S and E dynamics into common I models. This study will do this along a natural-to-urban forest structure gradient on the Georgia Southern University (GSU) campus using a regionally dominant species (Pinus taeda, loblolly pine). The study will couple existing biometeorological monitoring methods (meteorological, stemflow, and throughfall measurements) with novel terrestrial LiDAR techniques (LaserBark and L-Architect) to compare S and E in urban forests with directly, non-destructively measured canopy structural metrics. This addresses two questions: 1) how do across- and within-storm dynamics of S and E vary for 2 urban forest structures, and how does this compare to natural tree stands, and 2) to what extent can inclusion of directly-measured canopy structures in urban stands alter I outputs, parameters, and even parameterizations for the most commonly used models (i.e., the Gash- and Rutter-type)? These findings will advance nearly all hydrologic models that simulate or include forest interception processes. Six undergraduates supported by this proposal will receive substantial research experiences spanning the breadth of research activities (including field instrument training, installation, and maintenance; data collection and processing; modeling and model evaluation; manuscript preparation; and presentation at national meetings) in a timely and critical subfield of water resource management. Data will also be used to improve: 1) the L-Architect model, which is being incorporated into Computree, a tool used by the Office National des Forêts (France) for national improvement of forest inventories; and 2) the sustainable irrigation practices currently employed on the GSU campus.