生物结皮发育对毛乌素沙地土壤粒度特征的影响

以宁夏盐池荒漠生态系统定位研究站域内藻、地衣、苔藓3种不同发育阶段生物结皮及裸沙地为研究对象,应用激光衍射粒度分析技术测定土壤粒度组成,计算分析平均粒径、标准偏差、偏度、峰态值和分形维数等土壤粒度特征参数,研究结果显示:研究区土壤粒度组成以砂粒为主,约占土壤颗粒体积分数的80%~95%,而粘粒、粉粒含量较少;土壤粒度分布较为集中,分选状况较差,偏度状况为极正偏度,峰态值为很尖窄、尖窄;土壤分形维数分布于2.15~2.30之间,且从大到小依次为苔藓结皮、地衣结皮、藻结皮、裸沙地。在生物结皮发育过程中,土壤粘粒、粉粒等细粒物质不断增加;粒度组成不断优化,整体呈现向均匀和对称分布演化趋势。生物结皮能够有效改良土壤结构,促进土壤发育,但速度十分缓慢。

Effects of Biological Soil Crusts on Soil Particle Size Characteristics in Mu Us Sandland

To reveal the effects of biological soil crusts (BSCs) on soil particle size characteristics in Mu Us Sandland, soil samples under algae, lichens, and mosses crusts as well as the uncovered sandland were selected in Yanchi research station. Soil particle size distributions were identified by using laser diffraction technique. Particle size parameters were subsequently calculated including average particle size, standard deviation, skewness, kurtosis and fractal dimension. The results indicate that the majority soil particle size is occupied by sand particles approximately accounting for 80%~95% of the total volume; accordingly clay and silt particles contents are much less; soil particle size distributions in different sites are comparatively centralized that resulted in poor sorting, very positive skewness as well as sharp or very sharp kurtosis; the fractal dimension of soil increases progressively across the successional stages of BSCs in range of 2.15~ 2.30. In short, as affected by BSCs, clay and silt particles continue to increase leading to constantly particle distribution optimization, and soil particle size distribution inclines to uniform and symmetric pattern. Therefore, BSCs are beneficial to soil improvement and development, but rather slowly.