Effects of Climatic Change on Soil Hydraulic Properties during the Last Interglacial Period: Two Case Studies of the Southern Chinese Loess Plateau

The hydraulic properties of paleosols on the Chinese Loess Plateau (CLP) are closely related to agricultural production and are indicative of the environmental evolution during geological and pedogenic periods. In this study, two typical intact sequences of the first paleosol layer (S1) on the southern CLP were selected, and soil hydraulic parameters together with basic physical and chemical properties were investigated to reveal the response of soil hydraulic properties to the warm and wet climate conditions. The results show that: (1) the paleoclimate in the southern CLP during the last interglacial period showed a pattern of three warm and wet sub-stages and two cool and dry sub-stages; (2) when the climate was warm and wet, the soil saturated hydraulic conductivity decreased and the content of macro-aggregates increased, and when the climate was cool and dry, the soil saturated hydraulic conductivity increased and the content of macro-aggregates decreased, indicating that the paleoclimate affected both the grain size of wind-blown sediment and pedogenic process; and (3) in the soil water characteristic curves, the soil water content showed variation in peaks and valleys, indicating that the dust source and pedogenesis of the paleosol affected the water holding capacity. The findings confirmed that on the southern CLP, the warm and wet climate improved soil aggregate stability and water holding capacity, while reducing soil water conductivity. These results reveal the response of soil hydraulic properties to the climate evolution on the southern CLP, which indicate soil water retention and soil moisture supply capacities under an ongoing global warming scenario.