Abstract
Abstract. Understanding and describing the spatial characteristics of soil surface microrelief are required for modelling overland flow and erosion. We employed the multifractal approach to characterize topographical point elevation data sets acquired by high resolution laser scanning for assessing the effect of simulated rainfall on microrelief decay. Three soil surfaces with different initial states or composition and rather smooth were prepared on microplots and subjected to successive events of simulated rainfall. Soil roughness was measured on a 2×2 mm2 grid, initially, i.e. before rain, and after each simulated storm, yielding a total of thirteen data sets for three rainfall sequences. The vertical microrelief component as described by the statistical index random roughness (RR) exhibited minor changes under rainfall in two out of three study cases, which was due to the imposed wet initial state constraining aggregate breakdown. The effect of cumulative rainfall on microrelief decay was also assessed by multifractal analysis performed with the box-count algorithm. Generalized dimension, Dq, spectra allowed characterization of the spatial variation of soil surface microrelief measured at the microplot scale. These Dq spectra were also sensitive to temporal changes in soil surface microrelief, so that in all the three study rain sequences, the initial soil surface and the surfaces disturbed by successive storms displayed great differences in their degree of multifractality. Therefore, Multifractal parameters best discriminate between successive soil stages under a given rain sequence. Decline of RR and multifractal parameters showed little or no association.
Highlights
The surface of agricultural soils is built up from clods and aggregates arranged in a complex system of successive macro and/or microstructures
The aim of this study is to describe the characteristics of soil surface microrelief decay under simulated rainfall employing multifractal concepts and to compare the widely used statistical index random roughness (RR) with the multifractal quantification
Multifractal formalism was appropriated for analyzing the variability of point heights measurements on a 2×2 mm2 grid and could be a practical way of assessing the spatial heterogeneity of soil surface microrelief
Summary
The surface of agricultural soils is built up from clods and aggregates arranged in a complex system of successive macro and/or microstructures. Taken on a scale ranging from cm to mm, plays a very important role in increasing water infiltration and the amount of crop water available and reducing runoff on cultivated lands (Podmore and Huggins, 1981; Armstrong, 1986; Kamphorst et al, 2000). SSR has been demonstrated to influence water infiltration, splash amount, overland flow and runoff routing (Govers et al, 2000; Romkens et al, 2001; Gomez and Nearing, 2005), to reduce runoff velocity and, to decrease soil detachment and transport (Cogo et al, 1983) caused by water erosion. Tillage implements break-up soil and produce abrupt roughness increases. Type 3 consists of systematic differences in elevation produced by farm implements, such as furrows. Notice that rills and gullies may create oriented roughness when concentrated erosion occurs
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