Conceptual and Statistical Modes to Characterize Soil Materials, Landforms, and Processes

Within landscape units of interest to soil surveyors and to soilgenesis researchers, economic and physical constraints generally prohibit collection of sufficient data to develop adequate predictive models of spatial variability. Conceptual models are more legitimate at these scales, and modal concepts based on central‐tendency values can be used effectively to develop these models. Our objectives were to obtain central‐tendency values for genetically important properties of two similar New Hampshire soils, to use these values to quantify modal concepts of each soil, and to relate these modal concepts to depositional processes. We examined central‐tendency values of particle‐size distribution, porosity, landform relief, and drumlin axis ratios in nine map‐unit delineations of Becket and Marlow series (coarse‐loamy, mixed, frigid, Typic Haplorthods) in southern New Hampshire. Modal concepts of Becket and Marlow were successfully defined by these parameters: Marlow soils were significantly finer and less porous, and occurred on steeper, more linear drumlins than Becket soils. These properties indicate that till lodgement is singularly influential in the genesis of Marlow soils. Becket soils also exhibit some degree of till lodgement, but subsequent melting of ice lenses accounts for removal of finer particles, higher porosity, and lower relief and linearity. The modal concepts defined in this study enabled soil scientists to discriminate more efficiently between Becket and Marlow soils in mapping, and to develop process‐oriented models of these soils.