希拉穆仁荒漠草原风蚀地表颗粒粒度特征

以荒漠草原常见的耕作区、围封区、放牧区及旅游区4种土地利用类型表层土壤为研究对象,利用激光衍射技术分析了0~2 cm表层土壤粒度组成,计算并分析平均粒径、标准偏差、偏度、峰态及分形维数等粒度参数,探讨风蚀颗粒范围。结果表明:1希拉穆仁荒漠草原耕作区、围封区、放牧区及旅游区4种土地利用类型土壤粒度组成均表现为以砂粒和粉粒为主,黏粒含量较低,样地平均粒径数值依次变小,分选性逐渐变好,峰态平缓,分形维数数值逐渐减小,土壤颗粒组成依次粗化;偏度分别为负偏、近于对称、正偏和偏正偏,彼此差异明显,偏度可作为有效的粒度参数指标。2通过分析粒度分布频率曲线和土壤粒度累积频率间平均距离,显示研究区粒径为134μm和454μm附近颗粒为近自然状态下的易风蚀颗粒。各粒度参数及分维值均显示放牧和旅游加剧希拉穆仁草原表层土壤风蚀,土壤粒度分布范围变宽,整体向粗粒化方向发展。

Particle Size Characteristics of Wind Erosion Surface Soil in the Desert Steppe

The topsoil samples of 0 – 2 cm were collected from farming land, fenced grassland, grazing grassland and tourist area in Xilamuren desert steppe and used to investigate soil particle size characteristics. First,the soil particle size distributions were identified by laser diffraction technique. Second, the particle size parameters of average particle size, standard deviation, skewness, kurtosis, and fractal dimension were subsequently calculated. And then, the erosion particle range was discussed. The results indicated that: 1) the topsoil particles in desert steppe were mainly composed of sand and silt, while the clay content was extremely low. Soil particle size followed the order: farming land < fenced grassland < grazing grassland < tourist area. Soil particle size distributions were all in poor sorting. The kurtosis was medium, wide flat, wide flat and medium for farming land, fenced grassland, grazing grassland and tourist area, respectively. The fractal dimensions were 2.39, 2.26, 2.20 and 1.88 for these land using types. Correspondingly, the skewness of these land using types was negative, nearly symmetrical, positive skewness and partial positive, respectively. The skewness can be used as an effective particle size parameter. 2) Based on the analyses of frequency curves of soil particle size and the average distance, it was found that when soil particles were about 134μm and 454μm, which are the easiest to be erode by wind under near nature conditions. The particle size parameters and fractal dimension showed that the grazing and tourism accelerated wind erosion of topsoil in this region. Soil particle distribution was becoming wide, and soil coarse particles increased gradually.