Soil Series Differentiae Selected by Discriminant Analysis Based on Ranks

Abstract

AbstractSoils derived from parent materials weathered from sedimentary rocks of different chronostratigraphic units have been correlated as members of the Berks and Weikert series in Virginia. These correlations assume similar lithostratigraphic units. In an attempt to discriminate soils derived from four groups of parent materials weathered from rocks of different chronostratigraphic units, 34 properties were evaluated as differentiae by similarity of distributions among the parent materials and by contributions to discriminant functions. Selected properties had nonnormal distributions for one or more parent materials. Therefore, α‐levels associated with the ANOVA F‐test would not be maintained for these data. For this reason, the distribution‐free Kruskal‐Wallis test provides a more appropriate basis for comparison. In addition, Hotelling's T2 test assumes multivariate normality. Therefore, ranks were used to calculate the discriminant functions. The discriminant functions indicate that distinct groups are formed by soils derived from the Chilhowee group and from the Rome‐Waynesboro formation. Soils derived from the Chilhowee group contain lower amounts of available plant nutrients while soils derived from the Rome‐Waynesboro formation contain more feldspar in the sand and silt fractions. Soils derived from rocks of the Brallier, Chemung, Millboro, Martinsburg, and Athens formations are not discriminated by any combination of the 34 soil properties. Differentiae selected by discriminant analysis explain differences in soil responses to use and management observed by field soil scientists. Therefore, we conclude that classes produced by discriminant analysis provide more accurate predictions of soil responses than classes produced by a priori‐selected properties and limits in a hierarchical system. The simultaneous consideration of several properties approximates responses of soils as integrated systems.