Transformation of categorical field soil morphological properties into numerical properties for the study of chronosequences

Use of the Quantitatively Transformed Field Soil Structure Description of the US National Pedon Characterization Database to Improve Soil Pedotransfer Function

“…3b) are in agreement with results in Calero et al (2008). Increases of optimal scales from granular soil structure type to others such as blocky and prismatic were related to the clay content that was shown to be correlated to those classes (Calero et al, 2008). For aggregate sizes, soils can be grouped in two groups based on the sign of the optimal scaling values (Fig 3c).…”

“…Combining categorical variables with optimal scaling into the principal components maximizes the variance explained by the principal components for the data set (Calero et al, 2008;Ellis et al, 2006;Gifi, 1990;Meulman and Heiser, 1999). As an additional useful outcome, the optimal scaling can describe non linear relationships among those categorical variables and can also be useful for other analyses such as cluster analyses (Calero et al, 2008). In this study, texture and shape classes were assigned as multiple nominal types whereas the rest of the field morphological descriptions including size (Table 2) were assigned as ordinal type.…”

“…Shape, size, and grade (i.e., relative distinctness of soil structural units) of soil clods are considered to regulate many of the hydrological processes related to soil water, solute transport, and runoff from tilled landscapes (Holden, 1995;Levine et al, 1996;Lin et al, 1999;McKenzie et al, 1991;Pachepsky and Rawls, 2003). Previous studies confirmed that there is potential in using qualitative descriptions to assess the change of soil structure along a chronosequence (Calero et al, 2008;Schaetzl and Anderson, 2005), and for estimation of water retention and hydraulic properties (Levine et al, 1996;Lilly et al, 2008;Lin et al, 1999;Pachepsky and Rawls, 2003). Due to the non-numerical characteristics of soil structural descriptions, however, it is difficult to evaluate relationships among soil structural descriptions and other soil properties or hydraulic processes using most traditional PT methods .…”

Evaluating the use of weathering indices for determining mean annual precipitation in the ancient stratigraphic record

“…Following the approach used in chronosequence studies (e.g., Harden, 1982;Vidic and Lobnik, 1997;Calero et al, 2008), a numerical value was assigned to each property for either the entire B horizon, if thin, or for subdivisions of thicker B horizons that could be subdivided on morphologic grounds. Most B horizons can be subdivided, and, in those cases, the property value for each subdivision was multiplied by subdivision thickness.…”

Spatial arrangement of soil mantle in Glacis de Buenavista, Mexico as a product and record of landscape evolution

“…Targulian and Krasilnikov (2007) suggest that argic horizons can be formed in a period of 10 3 to 10 4 years, depending upon site conditions; reaching the advanced weathering status is even slower. Calero et al (2008) found that the development of clay accumulation and rubification in a chronosequence study in southern Spain was prominent in pre-Holocene soils. Bronger and Sedov (2003), who studied pedogenesis in calcarenite ridges in Coastal Morocco, detected advanced accumulation of kaolinitic clay only on landsurfaces older than 100,000 years.…”