Leaf Hydrophobicity and Canopy Storage Relationships of Common Species in Semi-Arid Environments of the Western United States

叶片表面对水滴的排斥（即叶片疏水性）是暴露于每日降水的生境中的植物物种之间的共同适应。在降雨过程中，叶片疏水性可能是影响冠层蓄水量的一个重要变量。冠层蓄水量是指在降雨期间，在水开始间接滴落之前，冠层所持有的水量。具有高度排斥叶片表面的物种可能会增加一个地点的穿透量，并导致冠层下更大的水文输入。科罗拉多斯普林斯市科罗拉多大学地理与环境研究系的柯蒂斯·霍尔德教授将研究美国西部半干旱地区常见物种的叶片疏水性对树冠储藏量的影响程度。具体而言，本项目的三个目标是确定叶片疏水性和冠层储存量是否因不同的叶片习性和生长形式而不同，比较计算叶片疏水性和冠层储存量的方法，以及确定叶片疏水性是否在叶面积的基础上影响冠层储存量。为了解决这三个目标，研究者将通过降雨模拟和浸泡法的质量平衡方法来测量冠层的储存能力。此外，研究者将通过使用数码相机和测角仪计算水滴与叶片表面之间的接触角来测量叶片的疏水性。每个物种的冠层特征（叶和木本面积、叶取向和叶表面特性）也将被确定。如果物种间叶片疏水性和冠层储水量差异显著，则流域的水文输入可能受到植被变化的显著影响。在此背景下，该项目将增加我们对水文过程的了解，并为流域植被覆盖的规划和管理提供信息，这些流域是市政当局的原水源区。该项目将通过研究叶片疏水性作为影响冠层蓄水量的机制的重要性，增强我们对流域内水文通量的理解。通过测量流域内常见物种的叶片疏水性和冠层储水量，本项目将提供关于叶片疏水性在森林水文模型中的重要性的信息，从而提高我们对城市流域水资源输送的理解。在这个项目中，一些本科生和研究生将通过直接参与实地数据收集获得宝贵的教育机会。

The repellency of a water droplet by a leaf surface (i.e., leaf hydrophobicity) is a common adaptation among plant species in habitats exposed to daily precipitation. Leaf hydrophobicity may be an important variable that influences canopy storage capacity during a rainfall event. Canopy storage capacity is the amount of water held by the canopy during a rainfall event before water starts to drip as indirect throughfall. Species with highly repellent leaf surfaces may increase the quantities of throughfall at a site and result in greater hydrological inputs beneath the canopy. Professor Curtis Holder in the Department of Geography and Environmental Studies at the University of Colorado at Colorado Springs will examine the extent to which leaf hydrophobicity influences canopy storage capacity in common species of the semi-arid Western United States. Specifically, the three objectives of this project are to determine if leaf hydrophobicity and canopy storage capacity differs between species with contrasting leaf habits and growth forms, to compare methodologies that calculate leaf hydrophobicity and canopy storage capacity, and to determine if leaf hydrophobicity influences canopy storage capacity on a leaf area basis. To address these three objectives, the investigator will measure canopy storage capacity by a mass-balance approach with rainfall simulation and an immersion method. Additionally, the investigator will measure leaf hydrophobicity by calculating the contact angle between a water droplet and the leaf surface using a digital camera and goniometer. Canopy characteristics (leaf and woody area, leaf orientation, and leaf surface properties) of each species will also be determined. If differences in leaf hydrophobicity and canopy storage capacity between species are significant, then hydrological inputs to a watershed may be significantly influenced by vegetation changes. Within this context, this project will increase our understanding of hydrological processes and inform the planning and management of vegetation cover in watersheds contributing as raw water source regions for municipalities. This project will enhance our understanding of hydrologic fluxes within watersheds by examining the significance of leaf hydrophobicity as a mechanism that influences canopy storage capacity. By measuring leaf hydrophobicity and canopy storage capacity of common species within a watershed, this project will provide information on the significance of leaf hydrophobicity in forest hydrology models that could enhance our understanding of the delivery of water resources from municipal watersheds. Several undergraduate and graduate students will receive valuable educational opportunities by participating directly in field data collection during this project.