Comparison of Soil Hydraulic Characteristics Under the Conditions of Long-term Land Preparation and Natural Slope in Longtan Catchment of the Loess Hilly Region

Abstract

Soil moisture plays a crucial role in maintaining the health and sustainability of dryland ecosystems. Terracing and other similar land preparations can reshape the natural slope and change underlying surface into different micro-landforms, which are significant for rainwater harvesting, erosion control, and vegetation promotion in arid regions. In this study, the Longtan Watershed in Dingxi region was selected as the study area. Based on in situ experiments, soil sampling analysis, and modeling simulation, the effects of land preparation and artificial vegetation (Fish-scale pit/Adverse grade tableland-Platycladus orientalis) on soil moisture characteristics curves and soil moisture constants were quantitatively analyzed. ①The land preparations could effectively improve the soil moisture content in the study catchment of Loess Plateau. Compared with natural slope, soil water content of land preparations increased by 1.883%(volume fraction) on average and fish-scale pit method and adverse grade tableland method enhanced the soil moisture by 29.69% and 15.55%, respectively. ② Compared with the natural slope, fish-scale pit and adverse grade tableland could significantly improve the soil hydraulic properties. After carrying out the land preparations, saturated soil water content and soil properties such as field capacity increased by 4.24%-11.40%, suggesting that land preparations can improve soil moisture and water supply ability. ③ Surface soil moisture characteristics were better than those of the underlying soil layers after land preparations. Compared with the natural slope, fish-scale pit and adverse grade tableland's shallow soil layer (0-20 cm) increased the moisture by 38.75% and 23.84%, respectively, whereas in the deep layer (60-80 cm) the increment of moisture were only 3.34% and 3.85%, respectively. This research provides scientific basis for vegetation restoration and land improvement in fragile semi-arid ecosystems.