Quantifying the structural characteristics and hydraulic properties of shallow Entisol in a hilly landscape

Abstract

. Entisols are widely distributed in the hilly areas of southern China. They are affected by serious soil erosion and extensive agricultural activities, the structural and hydraulic properties of particular Entisols may differ. Characterizing soil structure and hydraulic properties is important with regard to the development of an understanding of the hydrology and ecosystem functions of shallow Entisols. X-ray computed tomography was used to characterize and quantify the soil pore structure under four typical land use types (cropland, grassland, tea orchard and forest land) from a hilly landscape in South China and the hydraulic properties of the soil including its saturated hydraulic conductivity and water retention curve were measured. The results showed that the soils under the grassland retained 14 and 21% more water at saturation than those under the cropland and tea orchard, respec-tively. The Entisol in the forest land had a significantly larger macroporosity (0.214 mm 3 mm –3 ) compared with that in the cropland (0.117 mm 3 mm –3 ) and tea orchard (0.131 mm 3 mm –3 ). The contribution of pores with a diameter >4 mm as compared to the total computed tomography derived porosity was 62.4% in the forest land, while this size class contributed 69 and 47.3% to the total porosity in the tea orchard and grassland, respectively. The saturated hydraulic conductivity value was well correlated with the degree of anisotropy and the fractal dimension.