毛乌素沙地沙层剖面理化性状及其气候指示意义

Sand-Profile Physical and Chemical Properties of Mu Us Sandland and Climate Instructions

在陕北神木县各丑沟流域,研究了沙漠湖泊外围和干涸沙漠湖底50cm厚剖面的土壤机械组成、有机碳和全氮的分布规律。结果表明:①两剖面自下而上的发育特征为,浅色砂层→深褐色泥炭层→浅色砂层→深褐色泥炭层;浅色砂层有机碳、全氮含量较低,土壤颗粒粗质化,说明该时期植被稀少,气候干燥少雨,沙漠湖泊消失或退缩,土地沙漠化不断扩大。相反,深色泥炭层黏粉粒比例显著增加,有机碳、全氮含量也明显增大,说明此时气候适宜,温暖湿润,降水较多,沙漠湖泊湖面扩大,植被丰富,土壤生物活性高,有利于养分聚集,沙化环境得到改善;②不同层次土壤黏粉粒与土壤有机碳、氮呈显著的正相关关系,随沙漠化进程,C/N比值呈减小趋势,土壤有机碳含量的衰减显著于全氮含量;粗砂粒与土壤有机碳、氮呈负相关关系。

Through collecting soil samples distributing on the periphery and the dry lakebed of the desert lakes,soil mechanical composition,organic carbon and total nitrogen content on the 50 cm sample profile were measured. The comparability between two points shows：① soil sediment changed from bottom to up：light-colored sand→deep （brown） colored peat layer→light-colored sand→deep （brown） colored peat layer; the organic carbon and the content of nitrogen were very low with much soil coarse particles in light-colored sand layer,which indicated vegetation was scarce and the climate was arid during the period,the desert lakes disappeared or shrunk with the increasing desertification. On the contrary,the content of clay and silt in the dark-colored peat layer increased significantly,organic carbon,total nitrogen was high,which indicated the climate was warm and humid with much precipitation,desert lakes expanded,rich vegetation and high soil biological activity conducted to nutrient accumulation. Finally,the sandy environment was improved. ② the significant positive correlation between sticky silt and soil organic carbon and nitrogen was found,C/N ratio was decreasing with the desertification process,the attenuation of soil organic carbon was more significantly than total nitrogen did. Reversely,the coarse sand and soil organic carbon,nitrogen showed the negative correlation.