Diffusive Soil Transport and Hillslope Evolution

PIS将在山坡地貌的最新关键发展的基础上，研究与生物活动和地表雨滴有关的扩散土壤运移和山坡演变的综合理论。它们的目的是：(I)阐明描述这些过程的本构(运移)定律的基本成分和形式，论证运移与地表坡度或土壤厚度与地表坡度的乘积成正比的条件；(Ii)为山坡演变模型中使用的类扩散系数提供动力学理论的类比，说明它是土壤颗粒活性、颗粒大小、土壤孔隙度和土壤厚度的显式非线性函数，并间接与气候和生物条件有关；(3)利用高速摄像和颗粒追踪技术，通过实验获得雨滴输送本构定律的形式；(4)说明颗粒活度梯度在产生输送过程中的基本意义，并利用沙箱实验对雨滴输送进行演示，并利用实地测量的土壤性质和示踪颗粒对地下输送进行说明；(5)澄清地表和地下颗粒扩散、混合和分类的成分，说明这些过程如何促成山坡连锁带结构；以及(Vi)建立扩散输送和坡面演变的高级计算模式，以探索地表几何形状、土壤输送、土壤厚度和土壤生产之间的完全耦合，包括对外部和边界强迫的非线性响应。这项为期四年的计划将结合理论、实验、现场和计算部分。PIS的理论工作将集中于澄清：(I)颗粒扩散、混合和分选的成分-土壤深度和链状尺度；以及(Ii)本构运移规律的形式。PIS的实验/实地工作将：(I)侧重于雨水溅起的过程，以及土壤和土壤表面的颗粒混合和分类；(Ii)旨在测试/验证其工作的理论和计算方面。他们还将应用基于不连续谱元素方法的高性能算法来开发高级计算代码，以模拟土壤深度尺度上的颗粒行为，并模拟地貌尺度上的山坡演变。在地球表面过程中心(CESPR)的赞助下，该项目将涉及地貌学、流体力学、应用数学和高级计算方面的专家合作。这项工作的结果将是对日益增长的山坡地貌学理论基础的重大而关键的贡献。

PIs will pursue a comprehensive theory of diffusive soil transport and hillslope evolution associated with biological activity and surface rainsplash, building on recent, key developments in hillslope geomorphology. Their objectives are: (i) to clarify the fundamental ingredients and forms of constitutive (transport) laws describing these processes, demonstrating the conditions under which transport is proportional to the land-surface gradient or to the product of the soil thickness and surface gradient; (ii) to provide the analogue of a kinetic theory for the diffusion-like coefficient used in hillslope evolution models, demonstrating how it is an explicit nonlinear function of soil-particle activity, particle size, soil porosity and soil thickness, and indirectly related to climatic and biological conditions; (iii) to experimentally obtain the form of the constitutive law for transport by rainsplash using high-speed video and particle tracking techniques; (iv) to illustrate the fundamental significance of particle-activity gradients in producing transport, and demonstrate this using sandbox experiments for the case of rainsplash, and using field measurements of soil properties and tracer particles for the case of subsurface transport; (v) to clarify the ingredients of surface and subsurface particle dispersal, mixing and sorting, demonstrating how these processes contribute to hillslope catena structure; and (vi) to develop an advanced computational model of diffusive transport and hillslope evolution for exploring the full coupling between land-surface geometry, soil transport, soil thickness and soil production, including nonlinear responses to external and boundary forcing. This four-year program will mesh theoretical, experimental, field-based and computational components. The PIs theoretical work will focus on clarifying: (i) the ingredients of particle dispersal, mixing and sorting soil-depth and catena scale; and (ii) the forms of constitutive transport laws. PIs experimental/field work will: (i) focus on the process of rainsplash, and on particle mixing and sorting within soils, and at the soil surface; and (ii) be designed to test/validate the theoretical and computational aspects of their work. They will also apply high-performance algorithms based on discontinuous spectral element methods in developing advanced computational codes for simulating particle behavior at the soil-depth scale, and for simulating hillslope evolution at geomorphic scales. Under the auspices of the Center for Earth Surface Processes Center (CESPR), this project will involve collaboration of scientists expert in geomorphology, fluid mechanics, applied mathematics and advanced computations. The results of this work will constitute a major, and critical, contribution to the growing theoretical foundation of hillslope geomorphology.