陕北黄土高原土壤干层的分布和分异特征

Distribution and characters of soil dry layer in north Shaanxi Loess Plateau.

以人工刺槐林为研究对象 ,经大量野外调查和数据分析 ,研究了陕北黄土高原土壤干层的分布状况和分异特征 .结果表明 ,土壤干层在陕北黄土高原从南到北大范围内普遍分布 ,根据干化程度可分为 4个类型区 :1)以宜君为代表的高原沟壑区南部 ;2 )以富县、黄陵为代表的高原沟壑区北部 ;3)范围较广的丘陵沟壑区 ,该区又可分为南、西、北 3个小区 ,南区以延安、延长为代表 ;西区以吴旗、安塞为代表 ;北区以绥德、米脂为代表 ;4 )以神木为代表的风沙区 .受降雨量的影响 ,土壤干化程度具有明显的水平分异规律 ,即随着降雨量从南到北的减少 ,干化程度亦随之加重 ;受海拔高度、降雨入渗能力的影响 ,土壤干化程度在小范围的山地呈现明显的垂直分异规律 ,海拔愈高 ,干化程度愈严重 ;因土地类型的不同 。

Based on a whole survey and detailed analysis in artificial Robinnia pseudoscacia forestland,distribution and characters of dry layer in soil were studied in north Shaanxi Loess Platea.The results showed that soil dry layer was distributed universally from south to north in Loess Plateau,which can be classified into four zones according to the dryness:1)In southern gully zone represented by Ziwu Ridge and Huanglong Moutain in Yijun County,the soil dry layer was gentle,so if the appropriate measures were taken and water-saving facility were available or in water-abundant year,the shortage of soil water coull be alleviated;2)In northern gully zone represented by Fuxian and Huangling County,light soil dry layer occurs and was getting worse and we should pay close attention to this;3)In the large hill and gully zone,serious dry layer appears,it coull be subdivided into south,west and north plots.In south plot represented by Yanan and Yanchang County the dry layer was moderate;in west represented by Wuqi and Ansai County the dry layer was severe;in north represented by Suide and Mizhi County the dry layer was disastrous;4)In the windy sand zone represented by Shenmu County,since the precipitation decreased drastically and seriously sandy,very grave soil desiccation appeared.Also,soil dryness showed apparent horizontal differences with rainfall and the apparent vertical gradient in small hill area.