Quantifying the effect of surface sealing on post-fire runoff and erosion in the western U.S.

野火可以暂时使森林流域的径流和侵蚀速率提高几个数量级，这些加速的径流和侵蚀速率具有相当大的地貌、生态和社会意义。地表密封——形成一层非常低导电性的薄表面层——可能会导致火灾后径流和侵蚀的增加，原因可能是雨水引起的压实和分解，灰尘堵塞土壤孔隙，或者形成低导电性的灰烬结壳。然而，关于地表密封在多大程度上增加了火灾后的径流和侵蚀，所涉及的密封机制，或有助于增加密封潜力的因素，以及地表密封效果尚未纳入火灾后径流和侵蚀的预测模型的研究很少。该项目将进行密集的实地和实验室研究，以确定地表密封对美国西部野火后径流和侵蚀增加的影响程度；(2)确定表面密封的各种机制和导致密封形成概率增加的因素；(3)建立了基于火区土壤和灰分特性的火灾后地表密封概率预测模型。这项研究将以六个实地和实验室实验为基础。这项工作将导致对火灾后地表密封的定量、基于过程的理解，以及对野火相关径流和侵蚀过程的新理解。

Wildfires can temporarily increase runoff and erosion rates in forested watersheds by several orders of magnitude, and these accelerated runoff and erosion rates have considerable geomorphic, ecological and societal significance. Surface sealing -- the formation of a thin surface layer with a very low hydraulic conductivity -- may contribute to increases in runoff and erosion after fire either through rainsplash induced compaction and disaggregation, the clogging of soil pores by ash, or the formation of low conductivity ash crusts. However, there has been very little work on the extent to which surface sealing contributes to increased runoff and erosion after fire, the sealing mechanisms involved, or the factors that contribute to an increased potential for sealing, and surface sealing effects have not been incorporated into predictive models of post fire runoff and erosion. This project will conduct an intensive, field and lab based research study to (1) determine the extent to which surface sealing contributes to increased runoff and erosion after wildfires in the western U.S.; (2) determine the various mechanisms of surface sealing and the factors that lead to an increased probability of seal formation; and, (3) develop a predictive model of the probability of surface sealing after fires, based upon the soil and ash properties in burned areas. The research will be based on six field and lab experiments. The work will result in quantitative, process-based understanding of post-fire surface sealing and new understanding of wildfire related runoff and erosion processes.