Collaborative research: Enhancement of wind erosion by fire-induced water repellency

火灾通过改变土壤表面的物理化学性质来加强风蚀的作用仍未被探索。事实上，以前从未通过土壤拒水性分析研究过火-风蚀的反馈。该提案研究了新的基本土壤过程。即，火灾引起的土壤可蚀性增强？并为它们的解释提供了一个新的机制框架。最近的实验证据表明，被烧毁地区的可蚀性明显高于邻近未被烧毁的裸露土壤，这种差异显著影响了富含营养的土壤颗粒在整个景观中的再分配。为了解释这些实验结果，该项目将测试假设，即通过影响颗粒间结合力的强度，火灾引起的拒水性增强了土壤的可蚀性。它将显示导致火灾后土壤可蚀性增强的机制如何与火灾引起的土壤疏水性有关。这一中心假设将通过一系列从土壤颗粒到田野/景观尺度的实验室、实地和建模活动来验证。将测量和比较两个野外地点燃烧和未燃烧地区土壤的疏水性和其他相关的水力和化学性质。野外风洞将用于测量在燃烧和未燃烧地块上的风蚀阈值速度。另外，将在实验室对现场土壤以及经过疏水性处理的干净砂土进行风洞试验，直接测试疏水性对风可蚀性的影响。将建立一个理论框架，通过粒子间力的变化来解释可蚀性和疏水性的变化，原子力显微镜（AFM）将用于进一步验证直接测量土壤粒子间力的理论框架。现有的地表湿度对阈值风速影响的研究大多忽略了土壤拒水性的影响。传统上，火灾对土壤可蚀性的影响仅限于火灾使植被覆盖退化的明显能力，从而剥夺了土壤表面草和灌木植被的遮蔽作用。该建议认识到火灾引起的疏水性的重要性及其使燃烧区域比邻近的裸露（即冠层间）土壤更容易被侵蚀的能力，对干旱和半干旱地区典型斑块景观内沉积物和营养物质的再分配具有重要影响。更广泛的影响：该项目将包括对一名博士生和最多两名高中科学教师进行研究方法和研究成果展示方面的培训。它将通过整合PI正在开发的课程来支持教育，并为研究类似问题的不同小组之间的合作提供基础。将寻求代表性不足群体的成员加入研究小组。拟议的研究结果将通过学术期刊的出版物和会议发言加以传播。社会将受益于对控制风蚀过程的更好理解，风蚀是影响气候、农业和人类健康的广泛过程。

The role of fires in enhancing wind erosion by changing the physical-chemical properties at the soil surface remains unexplored. In fact, fire-wind erosion feedbacks have never been studied before through the analysis of soil water repellency. This proposal investigates new fundamental soil processes ? i.e., fire-induced enhancement of soil erodibility ? and provides a new mechanistic framework for their explanation.Recent experimental evidence suggests that the erodibility of burned areas is significantly higher than that of adjacent bare unburned soil and that this difference significantly affects the redistribution of nutrient-rich soil particles across the landscape. To explain these experimental findings, this project will test the hypothesis that by affecting the strength of interparticle bonding forces, fire-induced water repellency enhances soil erodibility. It will be shown how the mechanisms causing the enhancement of post-fire soil erodibility are associated with fire-induced soil hydrophobicity. This central hypothesis will be tested through a set of laboratory, field, and modeling activities at scales ranging from the soil grain to field/landscape scale. Hydrophobicity and other relevant hydraulic and chemical properties of soils from burned and unburned areas at two field sites will be measured and compared. A field wind tunnel will be used to measure the threshold velocity for wind erosion on burned and unburned plots. Additional wind tunnel tests of the soils from the field sites as well as clean sands treated to make them hydrophobic will be conducted in the lab to directly test the effect hydrophobicity on erodibility by wind. A theoretical framework will be developed to explain changes in erodibility with hydrophobicity by changes in interparticle forces, and atomic force microscopy (AFM) will be used to further validate the theoretical framework measuring soil interparticle forces directly.Most of the existing studies on the effect of surface moisture on the threshold wind velocity has ignored the effect of soil water repellency. The impact of fires on soil erodibility has been traditionally confined to the obvious ability of fires to degrade the vegetation cover thereby depriving the soil surface of the sheltering effect of grass and shrub vegetation. This proposal recognizes the importance of fire-induced water repellency and its ability of rendering burned areas more erodible than adjacent bare (i.e., intercanopy) soil, with important effects on the redistribution of sediments and nutrients within the patchy landscapes typical of arid and semiarid regions. Broader Impacts: This project will involve the training of a Ph.D. student, and up to two high school science teachers in the methods of research and of presentation of research results. It will support education by integration into a course being developed by the PI, and provide a basis for collaboration between different groups working on similar questions. Members of underrepresented groups will be sought for inclusion in the research team. The results of the proposed research will be disseminated through publications in scholarly journals and conference presentations. Society will benefit from the improved understanding of processes controlling wind erosion, a widespread process affecting climate, agriculture, and human health.