古尔班通古特沙漠树枝状沙丘土壤水分时空变异特征

认识沙漠土壤水分的时空变异性，是揭示沙漠生态系统生态-水文格局的基础。利用中子土壤水分仪的实测数据，对古尔班通古特沙漠树枝状沙丘土壤水分时空变异进行了系统分析。研究表明:① 沙丘不同部位土壤水分随时间具有一致性变化规律，上层土壤和下层土壤的变化趋势有所不同。0~1 m土层坡顶>坡中>坡脚，1~2 m土层坡脚>坡中>坡顶。② 土壤水分具有明显的季节变化和分层变化特征。春季是古尔班通古特沙漠土壤水分最丰富、变化最迅速的时期；0~40 cm、40~140 cm、140~200 cm土层土壤水分变异系数分别为13.56%、5.35%和0.80%，与不同土层水分来源和消耗以及植物根系分布相对应；不同土层土壤水分的变异强度要大于不同部位土壤水分的变异强度。③ 植被和地形对土壤水分的空间分异作用明显，沙丘坡脚处以及荒漠灌木梭梭根区始终存在土壤水分相对富集区。

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.