毛乌素沙地表土粒度特征及其空间变异

沙漠化土地表土粒度条件研究对于区域土地利用与恢复以及防控土壤风蚀沙化具有十分重要的意义。通过对毛乌素沙地表土粒度测定，采用矩法计算粒度参数，研究毛乌素沙地的表土粒度特征。结果表明：沙地内部各种土地类型的表土粒度主要集中于砂粒段（1000～50μm），含量为41．22％～97．63％，粉砂粒（50～2μm）含量为0—51．61％，黏粒（〈2μm）含量为2．71％～10．38％；半固定沙丘和移动沙丘的平均粒径值分别为145．491和157．563μm，较为接近，处于各种土地类型的较低状态；固定沙丘与耕地的平均粒径值分别为128．782和118．175μm，居于中间状态；草地和林地的平均粒径值分别为94．667和108．819μm，颗粒级配较为细小；土地类型中以移动沙丘的粒度组成最为粗化。移动沙丘和半固定沙丘分选较好，表现出极强的正偏和较尖的峰值；耕地、林地、草地也表现出正偏，但其偏移值较小，峰值也较为平缓。毛乌素沙地不同土地类型间粒度特征值存在明显差异，充分表明不同土地类型受风蚀作用的差异性和风蚀作用的阶段性。从不同土地类型表土粒度的空间变异来看，毛乌素沙地表层土壤平均粒径存在比较明显的由东北向西南逐渐变细的空间变异规律。

Topsoil particle-size distribution and its spatial variation in Mo Us Desert

In order to know the particle-size distribution of Mo Us Desert,top soil(0-5 cm) from grassland,woodland,cultivated land,fixed dune,semi-fixed dune and moving dune of Mo Us Desert were collected.We calculated particle-size parameters using Moment law computation to study topsoil particle-size distribution of the Mo Us Desert.The results showed: the topsoil particle-size of different sandy land types was mainly in sandy range(1 000-50 μm),and the content percentage was 41.22%-97.63%.Silt(50-2 μm) was 0-51.61%.Clay(<2 μm particles) was 2.71%-10.38%.The average particle-size of semi-fixed dune and fixed dune was 145.491 μm and 157.563 μm respectively,which was a lower level among the land types.The average particle-size of fixed dune and cultivated land was 128.782 μm and 118.175 μm,which was a medium level among the types.The average particle-size of grassland and woodland was 94.667 μm and 108.819 μm,grain-size of which was fine.The particle-size distribution of moving dune was coarsest.The particle-size classification of moving dune and semi-fixed dune was better,which showed a strong positive bias and a sharp peak.The average particle-size distribution of cultivated land,woodland and grassland also displayed a positive bias,but theirs drift rate was lower,the peak was also gentler.The particle-size distribution was significantly different among the land types of Mo Us Desert,which led to the difference of wind erosion.From the view of spatial variation,the average particle-size of topsoil changed the coarse particles to the fine particles gradually from northeast to southwest in Mo Us Desert.