Intrapedal cutans — lateral differences in their properties and their spatial clustering

Abstract

Measurements and numerical testing of spatial clustering of intrapedal cutans within individual peds have been made from six Bt horizons from two different, but commonly occurring Alfisols in southern England. Point-counting from sets of sequentially cut thin sections have been made from three planes, selected with respect to pedon anisotropy. Illuviation channel argillans have been individually traced, and lateral differences over short distances in their morphological and optical properties established. Also established is the discontinuity of many illuviation channel argillans and great variability in the size and distribution of their clusters. This mosaic of areas with contrasting sparse and dense numbers of intrapedal cutans, combined with abrupt lateral differences in the properties of illuviation channel argillans, are the modal responses in these soils to the process of clay translocation. This occurs through the complex pattern of open, tubular pores that characterises their blocky and prismatic peds. Thus, this characteristic, spatial and temporal, intermittent deposition of illuviation channel argillans is likely to be associated with their limited, subsequent partial removal. Also important are lateral movements in colloidal suspensions within and through the upper Bt horizons in the Aquic Hapludalf at Burghfield, as compared with dominating vertical movements in the Typic Hapludalf at Slough.