Earth, Wind, and Fire: Eolian Erosion in Burned Chaparral Landscapes

土、风和火：被烧毁的丛林景观中的风蚀

• 批准号: 0921440
• 负责人: Emmanuel Gabet
• 金额: $ 9.6万
• 依托单位: San Jose State University Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2013-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0921440&HistoricalAwards=false
• 关键词: Earth; Wind; Fire; Eolian; Erosion

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Fires in steep chaparral landscapes are often followed by catastrophic debris flows. Because of this threat, another potentially significant post-fire erosional process, wind erosion, has been under-appreciated. Observations from a burned area in Southern California suggest that wind erosion may be as important as runoff erosion in burned semi-arid landscapes. Although the removal of vegetation, which protects the soil surface from the wind, undoubtedly plays a role in higher rates of wind erosion from burned areas, fire-induced changes within the soil itself may be more important in increasing the vulnerability of the soil to eolian transport. Undisturbed chaparral soils are covered by a biotic mat, a dense network of fine chaparral roots overlain by algae, lichen, and moss, which acts to armor the soil underneath. High severity fires, however, appear to combust the biotic mat, leaving the soil exposed to the wind. In Southern California, large fires are often driven by Santa Ana winds that can reach hurricane speeds. Because the conditions for these winds generally occur from September to March, the areas scorched by fire are then subjected to high winds for many months. Field observations and satellite images testify to extreme rates of wind erosion under these conditions. This project will investigate the relationship between fire, the biotic mat, and wind erosion through a program of wind-tunnel experiments. Undisturbed soil surface samples, collected from chaparral hillslopes, will be subjected to controlled wildfire conditions in the laboratory to simulate fires of varying temperatures and durations. The samples will then be placed in a wind tunnel to determine their threshold friction velocity, a measure of the soil's erodibility by wind.The main impact of this project will be to provide information on a source of airborne dust that can affect human health in Southern California. It should have implications for many similar environments elsewhere. It has been estimated that airborne dust pollution is responsible for thousands of premature deaths annually in California; satellite images indicate that burned areas are important sources of dust blown westward to the Los Angeles area during Santa Ana conditions. One of the goals of this project is to develop relationships between easily measured soil parameters and wind erosion potential for use by air pollution control districts. This project will also provide an educational opportunity for an undergraduate student from a minority-serving institution.

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)提供资金的。在陡峭的丘陵地带发生火灾后，往往会发生灾难性的泥石流。由于这一威胁，另一个潜在的重大火灾后侵蚀过程--风蚀--被低估了。对南加州烧毁地区的观察表明，在烧毁的半干旱地区，风蚀可能与径流侵蚀一样重要。尽管保护土壤表面免受风侵袭的植被的移除无疑在火烧区更高的风蚀率中起到了作用，但火灾引起的土壤本身的变化可能更重要，因为它增加了土壤对风沙输送的脆弱性。未受干扰的茶园土壤被生物垫子覆盖，这是一个由细小的草席组成的致密网络，上面覆盖着藻类、地衣和苔藓，它们起到了保护下面土壤的作用。然而，严重的火灾似乎会烧毁生物垫子，使土壤暴露在风中。在南加州，大火通常是由可以达到飓风速度的圣安娜风驱动的。由于这些大风的条件通常发生在9月至3月，因此被大火烧毁的地区将遭受数月的大风。现场观察和卫星图像证明，在这些条件下，风蚀的速度非常快。这个项目将通过一个风洞实验项目来研究火、生物垫和风蚀之间的关系。从查帕尔山坡采集的未受干扰的土壤表面样本将在实验室的受控野火条件下模拟不同温度和持续时间的火灾。然后，这些样本将被放置在风洞中，以确定它们的阈值摩擦速度，这是土壤被风侵蚀的衡量标准。该项目的主要影响将是提供有关南加州空气中粉尘来源的信息，该粉尘可能会影响人类健康。它应该会对其他许多类似的环境产生影响。据估计，空气中的粉尘污染是加利福尼亚州每年数千人过早死亡的原因；卫星图像表明，燃烧区域是在圣安娜条件下向西吹向洛杉矶地区的粉尘的重要来源。该项目的目标之一是发展易于测量的土壤参数与风蚀潜力之间的关系，供空气污染控制区使用。该项目还将为来自少数族裔服务机构的本科生提供教育机会。