Soil physical and hydraulic properties under different land uses in the black soil region of Northeast China

Black soil is inherently productive and fertile but is subject to soil erosion. Understanding the distribution of soil physical and hydraulic properties of the soil profile under various land uses would help reveal the mechanism behind the degradation of black soil. In this study, we investigated the variation in soil physical and hydraulic properties with land uses and soil depths in the black soil area of Northeast China. Disturbed samples and undisturbed soil cores were collected from 0-100 cm soil depths under agricultural land (AL), forestland (FL), and shrub land (SL). Our results showed that the land use and soil depth significantly affected the soil bulk density (BD), field capacity (FC), capillary moisture capacity (CMC), saturated hydraulic conductivity (Ks), and soil water retention curve (theta(s) and alpha). Small macroaggregates accounted for most of the soil mass and were significantly higher in FL but lower in AL for the 0-50 cm of the soil samples. The FC, CMC, and Ks decreased, but the BD increased with the soil depth across the three land-use types. In addition, the soil in AL had a higher BD but lower CMC and Ks than the soil in FL and SL for most soil depths. These results indicated that land use can influence the variation in soil physical and hydraulic properties within the 0-100 cm soil depth, and agricultural use is a major reason for soil degradation in this black soil region.