Multivariate analysis of hydropedologically significant soil variables on cultivated semi-arid hillslopes

Abstract

Context Hydropedology bridges hydrology to pedology, and hillslope hydropedology is central in understanding topography–hydropedology interrelations. Aim The objective of this study was to statistically evaluate soil–hillslope hydropedology interrelations by multivariate analysis of hydropedologically significant soil variables (HSSVs). Methods A complete randomised 6 × 5 × 3 factorial experiment (six slope aspects, five slope positions and three soil horizons) was established. Twenty nine soil profiles were excavated and described on topslope, shoulder, backslope, footslope, and toeslope positions of hillslopes oriented in different directions. A total of 486 soil samples were taken from A, B, and C horizons at 174 sampling points and analysed for soil parametric properties. In addition, soil morphometric factors were described in the field and converted to their quantitative values. Relationships among HSSVs were analysed by Spearman’s correlation and principal component analysis. Association between HSSVs, soil horizonation and slope factors (slope aspect and position) was analysed by a multivariate factorial ANOVA. Results Slope aspect and slope position were dominant factors, which significantly affected (P < 0.05) variability in the majority of the HSSVs. Variability in clay and sand contents, bulk density, organic matter content, saturated hydraulic conductivity, and field capacity was significantly affected (P < 0.05) by these factors. Also, soil morphological variables of concentration factors (such as clay accumulation on the ped faces and pore walls), mottles, rupture resistance, stickiness, and plasticity were significantly (P < 0.05) controlled by these factors. Conclusions Clay content and abundance of concentration factors must be included in prospective similar studies, as they are key soil indicators of hydropedology. Implications Further studies should be conducted with different soils for an improved conceptualisation of hillslope-hydropedology interrelations.