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

野火可以使森林流域的径流和侵蚀率暂时增加几个数量级，这些加速的径流和侵蚀率具有相当大的地貌、生态和社会意义。表面封闭--形成具有极低水力传导性的薄表面层--可能通过雨水飞溅引起的压实和解体、火山灰堵塞土壤孔隙或形成低传导性火山灰结壳，导致火灾后径流和侵蚀的增加。然而，关于表面封闭在多大程度上有助于火灾后径流和侵蚀的增加、所涉及的封闭机制或导致封闭潜力增加的因素的研究很少，表面封闭效应还没有被纳入火灾后径流和侵蚀的预测模型。该项目将进行一项密集的现场和实验室研究，以(1)确定地表封闭在美国西部野火后增加径流和侵蚀的程度；(2)确定表面封闭的各种机制和导致密封形成概率增加的因素；以及(3)根据烧毁地区的土壤和火山灰特性，开发火灾后表面封闭可能性的预测模型。这项研究将基于六个现场和实验室实验。这项工作将导致对火灾后表面封闭的定量、基于过程的理解，以及对与野火有关的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.