ABSTRACT
Surface relief, or topography, represents the geometric composition of the surface. Unlike macro-scale surface topography, which remains relatively unchanged, soil microtopography sometimes changes rapidly. In agricultural fields, soil surface microtopography is altered by tillage operations, livestock trampling, consolidation, and erosion and deposition from rain and wind. Immediately after a tillage operation, soil microtopography consists of tillage marks, or oriented roughness, and randomly oriented, differently sized roughness elements from clods to individual grains. The chapter shows how scale-dependent models, especially the fractal concept, are applied to quantify roughness measures calculated from digitized microtopography. Using microtopographic data collected by the laser scanner, C. Huang and J. M. Bradford showed the semivariance roughness functions for fallow plots exposed to natural rainfall, and field and laboratory erosion plots under simulated rainfall. The semivariance, or the variogram, was used to plot the roughness function, and a combination of fractal and Markov-Gaussian processes was proposed to characterize roughness at different scales.
