Defining geographic soil bodies by landscape position, soil taxonomy, and cluster analysis

The key Soil Taxonomy is based upon the idea that certain properties can be used to define populations of soils from the soil continuum. The soil mapping paradigm is that similar soil populations exist within landforms, High taxonomic variability has been reported within numerous soil mapping units. The hypotheses in this paper are that for large scale mapping (i) Soil Taxonomy creates classes that are only partially related to landform and (ii) more homogeneous soil classes exist if different defining constructs are used. The objectives are to: (i) classify a sampling of soils within a 40-ha upland pasture using both Soil Taxonomy and cluster analysis, (ii) identify the distinctness and relationships of these samples to landforms, and (iii) compare the geographic distributions of soil classes identified by Soil Taxonomy and cluster analyses. Ninety-four soil properties were measured from 257 pedons along point transects. Cluster analysis identified three pedologically and geographically distinct groups. A single cluster group was identified for soils within the ridge landform, whereas the backslope landform was a mixture of all three groups, A significant relationship was found for soil attributes and slope profile curvature within the backslope landform, but predictive value was low. Soil Taxonomy produced 13 geographically indistinct classes that were partially related to cluster groupings. Cluster analysis appears to be useful for revealing patterns of soil homogeneity and for identifying relationships among soil properties and landforms. Numerical analysis may be a helpful supplementary method for correlating soil surveys with large soil databases, or for defining those soil attributes which distinguish mappable bodies from the soil continuum.