Use of Statistical Tests to Describe the Basic Distribution Pattern of Iron Oxide Nodules in Soil Thin Sections

Abstract

AbstractSoil formation is often associated with the spatial reorganization of soil components, particularly Fe oxides. However, the methods available to describe the spatial distribution of Fe oxides generally lack measurable parameters that allow comparison between different types of soils. In this work, we demonstrate the use of statistical methods (e.g., χ2 goodness‐of‐fit test, mean, variance, and cluster coefficient) to describe the basic distribution pattern of Fe oxide nodules in soil thin sections. Using a computer, we mapped the spatial distribution (i.e., x and y coordinates) of Fe oxide nodules in six soil thin sections from the B horizons of three sandy soils from Alberta, Canada. We calculated the statistical tests at a range of grid sizes (2–10 mm) with a Fortran program to (i) examine the effect of grid size on the statistical description of the distribution and (ii) determine the “appropriate scale of observation” for each thin section. We defined this scale as the grid size at which the mean number of observation is at least five, which was found to vary in size from 5 to 9 mm in our samples. We recommend the determination of the appropriate scale of observation before any statistical description of the Fe nodule distribution. In all but one of our six samples, the statistical distribution of nodules was clustered; the remaining one was uniform in distribution. The methods described in this study provide statistical methods whereby results from different studies can be compared.