Fractal and the statistical analysis of spatial distributions of Fe-Mn concretions in soddy-podsolic soils

Fe-Mn concretions are stable indicators of water regimes in loamy and clay podsolic and soddy-podsolic soils. Their spatial distribution is, in a larg e part, an inheritance of several processes in a heterogeneous soil medium. The objective of this study was to examine whether fractal models are appr opriate to describe the spatial distributions of concretions. Data were col lected at three locations in the Moscow region. At the first location, ther e were eight plots at depths from 13 to 34 cm and the distributions of conc retions larger that 0.5 mm were mapped by staining the individual concretio ns. At the remaining two locations, soil cores of different sizes were take n from two depths. Concretions were extracted from these cores and sieved t o separate them by size. A method of thorough sampling of the area was empl oyed that used estimates of fractal dimension for the every possible positi on a fixed geometrical form by using the box counting technique. These esti mates were studied statistically and by comparison with simulated data. We found concretion distribution on the fixed depth to have at least three com ponents. The first of them represents the background, i.e., it corresponds to the random and independent distributions of concretions. The second comp onent has fractal nature. The third component represents dense nests and it is probably connected with favorable conditions for microorganisms forming concretions. Estimated dimensions greater than 2.5 belong to the nest comp onent and less than 1.6-to the fractal one. The interval (1.6; 2.5) of them can be accounted for only by the random distribution. (C) 1999 Elsevier Sc ience B.V. All rights reserved.