泾河中游地区全新世成壤环境演变研究

根据长武ETC全新世土壤剖面的测定分析,探讨了该地区全新世成壤环境演变过程,阐明了先周时代土壤特征及人类耕作对成壤过程的影响。研究结果表明,全新世早期气候温和干燥,沙尘暴明显减弱,风尘堆积速率降低,具有轻微生物风化成壤作用;对应于全新世最适宜期,该地气候温暖湿润,生物风化成壤作用大于风尘堆积作用,为典型的黑垆土成壤期。从3 100 a B.P.开始,季风气候格局发生转变,气候干旱化,沙尘暴加剧,风尘堆积速率大于生物风化成壤速率,土壤资源自然退化,形成弱成壤层和黄土层,两层均属于全新世黄土L₀。先周时期耕作层对应古土壤层的顶部,土壤具有典型的团粒结构。3 100 a B.P.时的季风转变导致的气候干旱化与土壤退化促使了游牧民族南迁和"古公迁岐"事件的发生。

Holocene Environmental Change of Pedogenensis in the Middle Reaches of the Jinghe River Basin

Magnetic susceptibility,Total Fe,total organic carbon(TOC), CaCO_3 and Rb,Sr,Rb/Sr measurement in the Holocene in this region,have revealed the characteristics of the environmental change of pedogenensis during late 11 500 years,and human activities of the Predynastic Zhou had some influence on the pedogenensis.The results show that dust deposition was reduced because of the climate warming,and the biological weathering is beginning in the early stage of the Holocene.Between 8500-3100 a B.P.,pedogenic process was very strong.A layer of Heilu soil was formed on this region.From 3100 a B.P.,soil degradation is remarkable.A layer of Loess has been accumulated since 3100 a B.P.,which has the Heilu soil buried.This means that the last 3100 years is the dry period with intensified dust accumulation and soil degradation.The cultivating layer of the Predynastic Zhou(180-150cm) was corresponding with the late Holocene Climate Optimum(3350-3100 a B.P.).Monsoon transformation has led to climate aridity and soil degradation from 3100 a B.P.,which was the dynamic force of the southward migration of nomads from the steppe of the northern Loess Plateau and the Mongolia Plateau,and the people of the Predynastic Zhou of arable farming community was forced to move south to the Guanzhong Basin,and established their capital city "Qiyi" on the Zhouyuan loess tableland.