【摘要】 土壤水分与土壤粒度是影响灌丛沙丘植被与沙丘演变的重要因子。通过对毛乌素沙地南缘典型灌丛沙丘土壤粒度以及4月、7月的土壤水分的测定,揭示了沙丘各部位土层土壤含水量的时空变化特征与粒度分布规律:由于是降雨1h后采样,丘间地与丘顶0-10cm土层7月土壤含水量均随深度变化骤减。丘间地自表层至70cm深度范围的土层,受植被、降雨、太阳辐射等外界环境因子影响较大。丘顶四月表层被灌木老枝覆盖,从一定程度上抑制丘顶0-30cm土层土壤水分的蒸发,同时增加粗糙度,降低下垫面起沙起尘率,从而为维持水分平衡、防沙治沙提供手段;30-80cm间的土层7月土壤含水量较4月土壤含水量丰富,是由于7月正值雨季,雨水下渗土壤含水量较高。风况、植被条件、沙面活动程度决定各部位土壤含水量的变化幅度,根系分布与植被决定沙丘土壤水分的动态变化与拐点出现的土层深度。迎风坡、丘顶、背风坡、丘间地沉积物粒度特征相似,均以细砂为主,垂直结构中细砂、极细砂含量较高,其次为粉砂。黏土、中砂、粗砂、极粗砂含量随土层深度的增加变化不大,极细砂、细砂含量随土层深度增加变化起伏较大。更多还原

【Abstract】 Soil moisture and particle size are important for the vegetation and evolvement of nabkhas.Based on the measurement of particle size and soil moisture in April and July of typical nebkhas in the Mu Us Sandland,the paper reveals the spatial-temporal characteristics of soil moisture at different position of the nebkhas,and the distribution law of particle size:Due to the measurement that was made 1 hour after the rainfall in July,soil moisture fell with the depth in 0-10 cm soil layer of interdune and dunetop.Soil layer of interdune from 0 cm to 70 cm was influenced by environmental factors such as vegetation,rainfall and solar radiation.At the dunetop,the topsoil was covered by old wattle of shrub,which restrained the evaporation of soil moisture in 0-30 cm soil layer,increased roughness,reduced wind speed and sand blown activity,and supplied a method to maintain water balance;in 30-80 cm soil layer,soil moisture was richer in July than in April,because July was in rainy season,rainwater infiltration lead to rich soil water.Wind condition,vegetation and dune activity decided the soil moisture change at different position.Root distribution and vegetation decided soil water dynamic and the depth that inflexion occurred.The particle size characteristic was similar that fine sand content was the highest at windward,dunttop,leeward and interdune.In vertical structure,fine sand and very fine sand were high and silt was latter.Clay,medium sand,sand content changed little with the depth,very fine sand and fine sand content changed a lot with the depth.更多还原