Variations in and factors controlling soil hydrological properties across different slope aspects in alpine meadows

Slope aspect plays a vital role in hydrological processes by regulating soil physicochemical properties; however, its influencing mechanisms and effects on soil hydrological properties are poorly understood, especially in the Qinghai-Tibetan Plateau (QTP). In this study, two slope aspects, i.e. south-facing (SF) and north-facing (NF), were selected on the northeastern QTP, and their soil physicochemical and hydrological properties were examined. Our results showed that the 0-20 cm water holding capacity and water supply capacity were higher in the SF aspect than in the NF aspect, whereas they were lower in the SF aspect than in the NF aspect in the 20-50 cm soil layer. This suggested that the vegetation in the SF slope might suffer less from soil erosion owing to its higher topsoil water retention. Furthermore, the soil properties were also altered by slope aspect, with the clay content in the NF aspect being higher than in the SF aspect in the 0-50 cm layer, and reaching a significant value in the 30-50 cm soil layer. Besides, the soil total carbon (TC), total nitrogen (TN), and soil organic matter (SOM) were significantly higher in the SF aspect than in the NF aspect in the 0-20 cm soil layer. However, the 30-50 cm TC, TN, and SOM contents were significantly lower in the SF aspect than in the NF aspect. Overall, the soil water holding capacity and supply capacity were mainly controlled by SOM, followed by capillary porosity, total porosity, and soil bulk density. Thus, soil hydrological properties were significantly affected by the slope aspect, and topsoil water retention in the SF aspect was stronger than that in the NF aspect. These results provide significant insights for the vegetation recovery of degraded grasslands in alpine ecosystems.