Temporal and spatial variation of soil moisture in dendritic sand dune over Gurbantunggut Desert in central Eurasia

Understanding of the temporal and spatial variation of soil moisture in sand dunes is a fundamental part of exploring the ecological and hydrological pattern of desert ecosystem. The temporal and spatial variation of soil moisture is analyzed using neutron probe soil water data collected from the Gurbantunggut Desert in central Eurasia. Results show that the spatial variation of soil moisture in different locations over sand dunes exhibits high level of consistency over time. Vertically, the variation behaves differently with soil layers. In the top layer of the soil (0—1 m), the volumetric soil moisture content has the highest value at the top, following by the hill, and the driest value is found at the foot. The opposite is true for the sub-layer of the soil (1—2 m), where the highest value occurs at the foot, following by the hill, and the smallest value is found at the top. The variation of soil moisture exhibits significant seasonality and has a strong vertical structure. The soil moisture is the richest in spring, but changes most rapidly during the season. The values of the coefficient of variation (C_V) in soil moisture for the layers of 0—40 cm, 40—140 cm and 140—200 cm are 13.56%, 5.35% and 0.8%, respectively, which correspond well to the source of soil water, the evaporation loss and the distribution of shrub roots in different soil layers. The vertical variation of soil moisture is greater than that in the horizontal ones. The vegetation covers and topography have strong influences on the spatial distribution of soil moisture. There exists a water-rich region in the Haloxylon ammodendron root-zone and the foot of sand dunes.