Vegetative Roughness Controls on Aeolian Sediment Transport

植被粗糙度对风沙输送的控制

• 批准号: 0814153
• 负责人: Jack Gillies
• 金额: $ 30.01万
• 依托单位: Nevada System of Higher Education, Desert Research Institute
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0814153&HistoricalAwards=false
• 关键词: Vegetative; Roughness; Controls; Aeolian; Sediment

The type and distribution of vegetation in arid environments play a critical role in controlling the initiation of the wind-driven sediment transport system as well as the magnitude of the flux of sand and dust. Despite this knowledge, the role of natural vegetation is not well accounted for in present regional wind erosion models. Previous research indicates that the change in sand transport rate due to large solid non-erodible roughness elements is a function of both the size and the distribution of the elements. For vegetation its properties (e.g., porosity, flexibility, drag coefficients, distribution, etc.) create uncertainty as to how similar their effects are as compared to solid element roughness, which is typically assumed in current wind erosion models. This project will investigate through field-based experimentation, how plant community structure as characterized by its distribution pattern and associated aerodynamic properties affects sand transport by wind. The data needed to answer these questions will be collected at four sites within the USDA Jornada Experimental Range (JER), NM, where the landscape has changed from one dominated by grasslands to one that is becoming dominated by shrubs, with a resultant increase in wind erosion and land degradation. The four sites represent different stages of mesquite invasion at the JER. At each of the sites instruments will measure regional and local wind speeds, surface shear stresses, sand movement activity, and the vegetation distribution characteristics. This research will aid in the identification of key characteristics of vegetation that can be used to indicate either stability or the approach of a critical threshold that subsequently leads to an increase in wind erosion and environmental degradation. The results from this project will provide a means to more accurately quantify the effect of sparse vegetation on sediment transport thresholds and sand fluxes, which can be incorporated into regional wind erosion models.This research is designed to increase our understanding of the links between wind-driven sediment transport processes and vegetation in desert environments in general. Desert environments worldwide are under pressure from climate change as well as expanding populations and their need for resources. Vegetation plays a critical role in the stability of desert environments, specifically as a buffer against wind erosion and the often-associated dust emission process. However, as evident in parts of the Chihuahuan desert in the U.S. southwest some desert plant communities, by virtue of their survival mechanisms, can exacerbate wind erosion, leading to environmental decline. Vegetation can therefore both positively and negatively influence wind erosion processes and the results of this project will aid in determining the nature and degree of these influences under a variety of environmental conditions. Such knowledge can subsequently be used to aid in evaluating how climate change and human-induced pressures could exacerbate degradation in these sensitive areas.

干旱区植被的类型和分布对风沙输沙系统的启动和沙尘通量的大小起着重要的控制作用。尽管有这样的知识，自然植被的作用是没有很好地占在目前的区域风蚀模型。 以往的研究表明，由于大的固体不可蚀粗糙元素的输沙率的变化是一个功能的大小和分布的元素。 对于植被，其属性（例如，孔隙率、柔性、阻力系数、分布等）与固体元素粗糙度相比，它们的影响有多相似，这在当前的风蚀模型中通常是假设的，这产生了不确定性。 本项目将通过实地试验，调查植物群落结构的分布模式和相关的空气动力学特性如何影响风对沙的输送。 回答这些问题所需的数据将收集在四个网站内的美国农业部Jornada实验范围（JER），新墨西哥州，那里的景观已经从一个由草地为主的一个正在成为灌木为主，从而增加了风蚀和土地退化。 这四个地点代表了日本东部沿海地区牧豆树入侵的不同阶段。在每一个地点，仪器将测量区域和当地的风速、表面剪切应力、沙的移动活动和植被分布特征。 这项研究将有助于确定植被的关键特征，这些特征可用于表明植被的稳定性或即将达到一个临界阈值，而这一阈值随后会导致风蚀和环境退化的加剧。 该项目的结果将提供一种手段，以更准确地量化稀疏植被对泥沙输运阈值和沙通量的影响，这可以被纳入区域风蚀model.This研究的目的是增加我们的理解风驱动的泥沙输运过程和植被之间的联系，在沙漠环境中的一般。 世界各地的沙漠环境都受到气候变化以及人口增长和资源需求的压力。 植被在沙漠环境的稳定性方面发挥着关键作用，特别是作为防止风蚀和经常伴随的粉尘排放过程的缓冲。然而，在美国西南部的奇瓦瓦沙漠部分地区，一些沙漠植物群落由于其生存机制，可能加剧风蚀，导致环境恶化。因此，植被对风蚀过程既有积极影响，也有消极影响，本项目的结果将有助于确定各种环境条件下这些影响的性质和程度。 这些知识随后可用于帮助评估气候变化和人为压力如何加剧这些敏感地区的退化。