Changes in Soil Hydrological Retention Properties and Controlling Factors on Shaded and Sunny Slopes in Semi-Arid Alpine Woodlands

Abstract

Slope orientation significantly influences soil’s physicochemical properties and the soil hydrological environment. However, the regulatory mechanisms and effects, particularly in semi-arid highlands, remain poorly understood. This study investigated soil physicochemical and hydrological properties on shaded and sunny slopes. Results indicated that in the 0–20 cm soil layer, the water-holding capacity was higher on sunny slopes, while water retention in the 10–20 cm layer was significantly higher on shaded slopes. This suggests that vegetation on shaded slopes experiences less soil erosion due to higher topsoil water retention. Additionally, slope orientation altered soil properties: the electrical conductivity (EC) of the 0–20 cm soil layer was significantly higher on shaded slopes. Nutrient elements such as Ca, Cu, and Zn were also relatively higher on shaded slopes, whereas soil organic matter was significantly lower compared to sunny slopes. Overall, soil water-holding capacity and supply were primarily controlled by EC, followed by capillary porosity and nutrient elements like Ca, Mn, and Fe. Therefore, slope orientation has a significant effect on soil hydrological properties, with stronger topsoil water retention on shaded slopes. These findings offer valuable insights for vegetation restoration in semi-arid highland ecosystems.