Holocene climate and soil water balance in Baoji Region of Southern Loess Plateau

Abstract

In this paper, changes in the Holocene climate, soil water and soil resources in Southern Loess Plateau are studied based on field investigation, grain size and chemical analysis. The purpose is to reveal the impact of the Holocene environmental change on soil water and human activities. The study shows that the mid-Holocene paleosol S0 in Baoji Region had a CaCO3 content close to 0, was enriched with Fe2O3, Al2O3, was of homogenous dense silty microstructure containing red argillans and had moderate chemical weathering. This shows that the paleosol is luvisol. The mean annual precipitation was about 800 mm at that time. The late-Holocene loess had a high CaCO3 content, low Fe2O3 and Al2O3 content and of pore-developed crumb microstructure, indicating that the climate was cold and dry. The migration depth of CaCO3 and Sr in the mid-Holocene paleosol indicates that the distribution depth of gravity water in the soil at that time reached 1.8 m, and the water content in the soil above 1.8 m during the vegetation growing season was higher than 20%. This made it suitable for the development of forest vegetation. The migration depth of CaCO3 in the Holocene loess was small and the water content in the layers of loess during rainy season was generally lower than 12%; thus, it was not suitable for the development of forest vegetation. In the mid-Holocene soil, water intake was greater than water consumption and soil water was positive balance. Moreover, trace elements, organic matters, water holding capacity and water content in S0 were higher than those in the early-Holocene and late-Holocene loess, which facilitated agricultural production and human activities. In fact, it is also the primary reason that the mid-Holocene village sites are significantly larger in quantity and greater in scale than the early-Holocene and late-Holocene village sites.