R.J Mikula

Bio: R.J Mikula is an academic researcher. The author has contributed to research in topics: Porosimetry & Fractal dimension. The author has an hindex of 1, co-authored 1 publications receiving 292 citations.

Upscaling Hydraulic Properties and Soil Water Flow Processes in Heterogeneous Soils: A Review

Abstract: This review covers, in a comprehensive manner, the approaches available in the literature to upscale soil water processes and hydraulic parameters in the vadose zone. We distinguish two categories of upscaling methods: forward approaches requiring information about the spatial distribution of hydraulic parameters at a small scale, and inverse modeling approaches requiring information about the spatial and temporal variation of state variables at various scales, including so-called “soft data”. Geostatistical and scaling approaches are crucial to upscale soil water processes and to derive large-scale effective fluxes and parameters from small-scale information. Upscaling approaches include stochastic perturbation methods, the scaleway approach, the stream-tube approach, the aggregation concept, inverse modeling approaches, and data fusion. With all upscaling methods, the estimated effective parameters depend not only on the properties of the heterogeneous flow field but also on boundary conditions. The use of the Richards equation at the field and watershed scale is based more on pragmatism than on a sound physical basis. There are practically no data sets presently available that provide sufficient information to extensively validate existing upscaling approaches. Use of numerical case studies has therefore been most common. More recently and still under development, hydrogeophysical methods combined with ground-based remote sensing techniques promise significant contributions toward providing high-quality data sets. Finally, most of the upscaling literature in vadose zone research has dealt with bare soils or deep vadose zones. There is a need to develop upscaling methods for real world soils, considering root water uptake mechanisms and other soil–plant–atmosphere interactions.

Applications of fractals in soil and tillage research: a review

Abstract: Fractals are spatial and temporal model systems generated using iterative algorithms with simple scaling rules. This paper reviews the literature on spatial fractals as it applies to soil and tillage research. Applications of fractals in this area can be grouped into three broad categories: (i) description of soil physical properties; (ii) modeling soil physical processes; (iii) quantification of soil spatial variability. In terms of physical properties, fractals have been used to describe bulk density, pore-size distribution, pore surface area, particle-size distribution, aggregate-size distribution, ped shape and soil microtopography. In terms of physical processes, fractals have been used to model adsorption, diffusion, transport of water and solutes, brittle fracture and fragmentation. In terms of spatial variability, fractals have been applied to quantify distributions of soil properties and processes using semivariograms, power spectra and multifractal spectra. Further research is needed to investigate the specificity of different fractal models, to collect data for testing these models, and to move from the current descriptive paradigm towards a more predictive one. Fractal theory offers the possibility of quantifying and integrating information on soil biological, chemical and physical phenomena measured at different spatial scales.