基于土壤粒度参数的荒漠草原地表粗粒化过程

草原退化特征已由植被变化为主演变为土壤退化的阶段,其植被覆盖变化可在一定程度上反映退化状况与过程,探明荒漠草原不同退化阶段(覆盖度)地表风蚀状况,对合理利用与保护草地资源意义重大。以希拉穆仁荒漠草原7个覆盖度(裸地,5%,20%,40%,60%,80%和100%)下的表层土壤为研究对象,利用激光衍射技术测量表层0—1cm土壤粒度组成,分析不同覆盖度下的平均粒径、标准偏差、偏度、峰态及分形维数等粒度参数变化情况及颗粒频率分布。结果表明:(1)土壤粒度组成均以沙粒和粉粒为主,黏粒含量较低;偏度可作为有效粒度参数指标。(2)随着盖度降低,平均粒径数值越大,分选性越好,频率曲线由近于对称—正偏—极负偏转变,峰态由尖锐变平缓,分形维数先增加后降低。(3)粒径分布基本呈双峰分布,盖度越小第二波峰滞后越明显,且分布均匀程度越低,易风蚀颗粒范围为144~869μm。

Soil Coarse Graining Process Based on Surface Grain Size Distribution in Xilamuren Desert Steppe

Grassland degradation characteristics have been transformed by changes in vegetation primarily for soil degradation stage,to a certain extent,its vegetation change can reflect the status and process of degradation.The wind erosion situation of different degradation stage in Xilamuren desert grassland was studied,which is of great significance for protecting and utilizing grassland resources in this area properly.In this research,the top soils (0-1 cm) of 7 different types of vegetation coverage (0％,5％,20％,40％,60％,80％ and 100％) were selected.In order to analyze the soil particle size characteristics in desert steppe,laser diffraction technique was used to identify the soil particle size distributions,and the particle size parameters such as the average particle size,standard deviation,skewness,kurtosis and fractal dimension were calculated.The results indicated that:(1) most topsoil particle sizes in desert steppe were mainly sand and silt,while the clay content was low;(2) With the decrease of the coverage,the average particle size became bigger,the sorting characteristics got better and the frequency curve changed by nearly symmetrical to positive skewness and partial negative skewness eventually,the kurtosis changed from the sharp to the flat,fractal dimension increased first and reduced later;(3) the particle size distribution was bimodal distribution,the smaller basic coverage was,the more obvious of the second wave lagged behind,and the lower level of uniform distribution was,the more coarse of particle size of the particles concentration was.