Soil-grain transport and dispersal by rainsplash, with implications for plant-soil interactions in deserts

这个项目涉及到描述雨水飞溅引起的土壤迁移。通过考虑雨滴激活土壤-颗粒运动的间歇性，该公式表明雨滴强度的梯度在影响运移方面可以与地面坡度一样重要。该公式为描述雨滴对土传病原体和养分的传输、扩散和隔离提供了一个实用的框架。基于最近在澄清谷物飞溅过程的物理方面取得的成功，该项目结合了理论、实验和现场工作，以：(I)加深对雨滴引起的土壤-颗粒运输和扩散的理解；以及(Ii)阐明沙漠灌木下沉积物的储存和释放与雨滴有关的行为如何代表电容器的行为？这有助于确定沙漠地表演变的速度。实验包括对水滴撞击过程中泥沙颗粒输送的高速成像，以及在受控降雨条件下测量泥沙颗粒的输送和扩散。野外工作包括测量美国西部沙漠灌木下和周围的土壤特征，目的是澄清植被树冠和土丘的特征长度尺度与谷物飞溅之间的关系。除了有助于更清楚地了解雨滴运输作为一个重要的地貌过程，该项目还将把雨滴的物理细节与专注于农业和沙漠环境中污染物、养分和病原体的传输、扩散和隔离以及沙漠植被生态的研究联系起来，其中沙漠植物被视为资源岛。在这个项目中支持的研究生将获得与地球表面系统以及其他地球科学和工程领域相关的流体力学和传输现象的基础。本科生将大量参与，从而完成高级论文项目。该项目将生成引人注目的雨滴图像和视频，从视觉上阐明这一过程。科学界和公众将很容易通过教育网页获取这些信息。该奖项将得到美国国家科学基金会地貌学和土地利用动力学项目(EAR/GLD)的支持。

This project involves describing soil transport by rainsplash. By taking into account the intermittency of soil-grain motions activated by raindrops, the formulation indicates that gradients in raindrop intensity can be as important as surface slope in effecting transport. The formulation provides a practical framework for describing transport, dispersal and sequestration of soil-borne pathogens and nutrients by rainsplash. Building on recent success in clarifying the physics of the grain splash process, the project combines theoretical, experimental and field-based work to: (i) pursue a deeper understanding of soil-grain transport and dispersal by rainsplash; and (ii) illustrate how storage and release of sediments beneath desert shrubs in relation to rainsplash represents the behavior of a ?capacitor? that contributes to setting the rate of desert land-surface evolution. Experiments involve high-speed imaging of sediment grain transport during drop impacts, and measurements of transport and dispersal under controlled rainfall conditions. Field work involves measurements of soil features beneath and surrounding desert shrubs in the western U.S., aimed at clarifying relationships among the characteristic length scales of vegetation canopies and soil mounds in relation to grain splash.In addition to contributing to a clearer understanding of rainsplash transport as an important geomorphic process, the project will connect the physical details of rainsplash with studies focused on transport, dispersal and sequestration of contaminants, nutrients and pathogens in agricultural and desert settings, and on the ecology of desert vegetation, wherein desert plants are viewed as ?resource islands.? Graduate students supported during this project will gain a foundation in fluid mechanics and transport phenomena relevant to Earth-surface systems as well as other geoscience and engineering fields. Undergraduate students will be substantively involved, leading to senior thesis projects. The project will generate compelling images and videos of rainsplash that visually clarify this process. These will be readily accessible to the science community and public via educational web pages.This award will be supported by the NSF's program in Geomorphology and Land-Use Dynamics (EAR/GLD).