Scale-dependent covariance of soil physical properties above and below a soil horizon interface: Pedogenic versus anthropogenic influences on total porosity

Abstract

Dyck, M. F. and Kachanoski, R. G. 2011. Scale-dependent covariance of soil physical properties above and below a soil horizon interface: Pedogenic versus anthropogenic influences on total porosity. Can. J. Soil Sci. 91: 149–159. The basic unit of soil – the pedon – is described as the minimum, three-dimensional unit of soil representative of the variability of soil horizon dimensions and morphology. Pedogenic processes responsible for soil horizon and soil profile formation are primarily hydrologic in nature. The spatially variable distribution of soil horizons (i.e., the variation among pedons within catenae or landscapes) is likely a reflection of the inherent variability of the soil parent material and the spatial variability of hydrological/pedogenic processes. This paper explores the spatial variability and spatially scale-dependent covariance between a basic soil property (porosity) above and below an A/B horizon interface under adjacent disturbed (cultivated) and undisturbed (forested) conditions. A combination of scale-dependent variance and Fourier-domain spectral analysis shows that the scale-dependent covariance of A and B horizon porosity varies significantly between the cultivated and forested sampling transects. The majority of these observed differences between the scale-dependent covariance of A and B horizon porosity under contrasting land uses is attributed to tillage. These results suggest that anthropogenic activities such as tillage may not only alter the surface horizons, but the nature of the spatial covariance between surface and underlying horizons which likely influences current soil hydrological processes.