Soil Architecture and Its Functional Manifestations: A New Era for Soil-Landscape-Hydrology Research?

Revolutionaries in science often root in the understanding of fundamental structure of natural systems (e.g., DNA for biology, atoms for physics, and elements for chemistry). The same is true for the study of soils and landscapes (e.g., molecular structure for water properties, mineral structure for clay behaviors, and landforms for geomorphic processes). A new era of soils research is to be “structure-oriented,” passing the stage of “texture-focused.” While considerable knowledge on soil structure has been amassed over decades, a comprehensive theory and an effective quantification of soil structure across scales is still lacking. To propel the field forward and out of the stagnation, thinking outside “the box” is needed to embrace the broadest sense of soil structure (termed “soil architecture”, reflecting hierarchical levels of soil structural complexity from the molecular level to the landscape scale) and to encompass pedality (aggregation), pore space (networks of openings), and their interfaces (including surface features of peds). We also need to go beyond the traditional scale of soil aggregates to include soil profile architecture (e.g., water-restricting soil horizons) and landscape architecture (e.g., landforms and stratigraphy). To represent soil architecture in a manner that can be coupled into models of flow, scaling, and rate processes, noninvasive quantification and continuous mapping of soil architectural patterns across multiple scales are essential. Such advances would allow the integrated studies of physical, chemical, biological, and anthropogenic forcing on soils in the landscape context. Interfaces are among the critical controls in understanding the landscape-soil-water-ecosystem dynamics, including macropore-matrix interface, soil horizon interface, ped interface, water-air interface, soil-root interface, microbe-aggregate interface, soil-bedrock interface, soil-atmosphere interface, and soil-water table interface. This invited presentation will illustrate the above points using specific examples, with a focus on soil architecture and preferential flow from the pore level to the landscape scale.