Studying the spatial structure of pedodiversity (Shannon's entropy) as related to the land area – An example from Czechia

Abstract

Shannon's entropy is often used to express the magnitude of soil diversity, but its applicability for the study of spatial structure of pedodiversity is limited by its nature of characterizing the entire monitored area with only one value. However, by adopting the concept of potential pedodiversity (PPD) (soil diversity at each raster cell computed from its circular surroundings of a defined radius) that has no such limitation, the spatial structure of pedodiversity and its relation to the land area could be studied. By gradually increasing the radius of the circular surroundings (and hence the total land area), it has been shown that the spatial structure as described by experimental semi-variogram is inseparably linked to the size of the land area taken for evaluation. The larger the land area, the larger the expected sill and range values of the semi-variogram. In addition, the general shape of the semi-variogram also changed significantly as the land area changed. This suggests that different variogram models to fit the experimental semivariograms for PPD patterns differing in land area would be appropriate. Moreover, the general shape of the semi-variogram may indicate how evenly the pedodiversity is spatially distributed, e.g., occurrence of hotspots and the distance at which they are spaced apart. On top of that, the results showed that the limitation of Shannon's entropy (as well as other abundance related diversity measures) for comparing areas of different sizes (as it was found that larger areas tend to have a larger index value) can be avoided by comparing the characteristics of the most contrasted PPD pattern, i.e., the radius of the cell circular surroundings, mean value, standard deviation, minimum and maximum values), on which the total land area has no effect. For such comparisons, the general shape of the semi-variogram of the most contrasted PPD pattern could also be a useful comparative parameter showing mainly the character of soil diversity spatial distribution.