Scale and scaling in soils

Authors: Pachepsky, Yakov; HILL, R - UNIVERSITY OF MARYLAND

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2016
Publication Date: 1/6/2017
Citation: Pachepsky, Y.A., Hill, R.L. 2017. Scale and scaling in soils. Geoderma. 287:4-30.

Interpretive Summary: Soil samples are typically small, yet results of sample analysis have to be used to substantiate policy, regulations, and management decisions across large areas, watersheds, and regions. The transfer of information from small scales to large scales, and vice versa, has become a central problem in making the environmental sciences to serve society. The latest book on this matter was published under our editorship in 2004. Since no courses on scale and scaling are offered in U.S. universities, the objective of this work was to present a document of manageable size, based on the major scaling ideas used in soil science, that could serve as an introductory course and point to the main or representative references. Note that scaling concepts, ubiquitous in soil science, have received a substantial attention and development the last ten years with the advent of “big data”. Results of this work will be useful to soil professionals and to environmental scientist in general in that they provide a systematic introduction in opportunities, needs, and feasibility of mutually beneficial soil information transfer between scales, scientists, policymakers, and public.

Technical Abstract: Scale is recognized as a central concept in the description of the hierarchical organization of our world. Pressing environmental and societal problems such require an understanding of how processes operate at different scales, and how they can be linked across scales. Soil science as many other disciplines obtain bulk of their empirical information at fine scales, whereas results of environmental diagnostics, monitoring, and predictions are needed to make decisions at much more coarse societally important scales. It becomes imperative to relate information available and produced at different scales. The objective of this work is to present an overview of concepts that are currently used to define and relate scales in soil studies. The paper is not intended to be a compendium, but rather should be viewed as a material for discussion, reference, and critique. It discusses definitions and terminology, including general approaches of scale problem in environmental studies that are applicable to soils, including hierarchies, measurement metrics, similitude, non-geometric scale metrics, and notions of upscaling and downscaling. Concepts of general scaling methods and theories are dimensional analysis, power law scaling, space and time dependent scaling. A section on spatiotemporal patterns introduces scaling ideas that were used in soil studies such as empirical orthogonal functions, data assimilation, and cumulative distribution function matching. Reviewed scaling methods developed specifically to soil studies include geometric similitude of pore spaces, scaling with Richards equation, scale dependencies of water and solute flux model parameters, scaling based on temporal stability, overland flow and sediment transport as the scaling phenomenon, and the relevance of scaling to pedotransfer. The outlook of scaling research in soils is presented that shows needs and feasibility of enriching and advancing soil research that faces grand challenges of modern times.