Nested subset analysis and taxa-range size distributions of pedological assemblages: implications for biodiversity studies

A common pattern of taxa distribution has been termed nested subsets by ecologists. Species present in any particular biological assemblage tend also to be present in larger assemblages. The same is true for the so called species-range size distribution: locally abundant species tend to be widespread, whereas locally rare species tend to be narrowly distributed. According to several ecologists, this pattern could be described by a power law. In this paper we show that regularities tested with our data (soil types = pedotaxa, and soilscapes = pedological assemblages) are surprisingly similar to those in ecological literature. For this purpose several soil data sets, as well as techniques utilised in mathematical ecology, including Atmar and Patterson's Nested Calculator Program have been used. Many of these common patterns appear at different spatial scales suggesting that mechanisms such as nestedness, taxa-range size distributions and species-area relationships among others could be scale invariant, as some ecologists claim. Our results show that nestedness and scale-independent taxa-range size distributions are not exclusive properties of biological assemblages, but can be found in a broader class of earth systems. Pedodiversity analysis also has practical implications for designing reserves for biological and pedological conservation.