Vertical distribution characteristics of soil moisture with different strata in deep profile in Guanzhong Basin, China

The distribution of soil moisture in loess-paleosol sequences is a critical factor that impacts the regional environment in the Chinese Loess Plateau (CLP). In this study, samples were collected from the Xiushidu (XSD) profile at the southern edge of the Jinghe River in Guanzhong Basin; specifically, the Holocene-Middle Pleistocene Lishi strata loess. They were then dry weighed, and moisture content and grain size distribution were determined using the grain size testing method. The impacts of different soil textures, sedimentary environments and other factors on the XSD profile moisture distribution in the study area were examined. The results showed that: (1) During the sequence change process from top to bottom, the soil moisture content of the loess-paleosol sequence increased and the overall average moisture content of the XSD profile was ranked in a descending order as: the middle layer of Middle Pleistocene Lishi loess>the upper layer of Middle Pleistocene Lishi loess>the Holocene>the Late Pleistocene; (2) When film water was predominant, the correlation coefficients for soil moisture content and clay, fine-silty sand, coarse silt sand and microsand content were 0.389, 0.394, -0.419 and -0.451, respectively; (3) In adjacent loess and paleosol layers, the soil moisture content of the overlying loess layer was always greater than the underlying paleosol layer. (4) In the same loess layer, minimum moisture content values were subject to the East Asia winter monsoon; as such, they often appeared in the middle layer of this glacial period. In the same paleosol layer, the opposite trend was observed.