长城沿线毛乌素沙地形成、扩展及其荒漠化效应

地质历史时期“河套古湖”退缩残留的湖滨沙堤受风力作用“就地起沙”,是毛乌素沙地形成的物质基础。受自然环境动态变化与人类不合理活动的影响,历时时期毛乌素沙地的土地利用和经济方式发生过“游牧为主-亦牧亦农-农耕为主”的反复变化。唐代以至明清时期,长城沿线毛乌素沙地土地沙化有愈演愈烈之势,并在不同地段,分别以片沙蔓延、沙舌扩展、河谷沙化及宽带沙舌等形式向东南方向扩展。此种现象不仅造成本地区土地类型改变、植被摧毁和土壤侵蚀加重等,也引起毗邻地区沙尘暴频率和影响范围增大、加重黄土区土壤侵蚀及河流粗沙输沙率等荒漠化效应。

Researches on the Formation,Expansion and Desertification Effects of Maowusu Sandy Land Along the Great Wall

The lake shore sandy dike in the shrinking process of"Hetao ancient lake"in the geologic period,which is suffered from the wind force function "rises right on the sandy land",is the substantial basis of the formation of Maowusu sandy land.Suffered from the natural environmental development and the Human's inconsequential activities,Maowusu sandy land in the history has undergone the reiterative change of "the nomad way of life is the main nomadism as well as agriculture-agriculture is the main".From Tang Dynasty to Ming and Qing periods,the desertification of the land turned to stronger and stronger,and there were different expand modes toward the Southeast in different districts,such as spreads with sheet sand,expands with sand tongues,spreads along the river valley and expands with the wide zonal sand tongue.This desertification is not only resulted in the changes of the land's type,the destruction of the vegetation and the erosion of the soil is aggravated in the local area,but also causes the frequency and the affective scope of the sandstorm enlarges and aggravates the erosion of the soil and the rate of schlepping sand with the river in the adjacent loess areas.