历史时期乌兰布和沙漠环境变迁的再探讨

文章应用历史地理学方法，结合现代水文、河流、地貌、沉积等学科的研究成果，对历史时期乌兰布和沙漠北部环境变迁问题提出以下观点：1)乌兰布和沙漠北部在先奏为古屠申泽，其湖面远大于西汉至北魏时的屠中泽；2)西汉至北魏时屠中泽向北萎缩，湖面减为原来的44％，西汉所置窳浑，临戎、三封3县即位于河湖之滨的绿洲之上；3)黄河干流中滩～协成段受科里奥利力作用的影响，右岸冲刷较多，是该区黄河多次改道东移的惟一原因．黄河迳流是古屠申泽得以存在的惟一水源，故黄河改道是该湖不断萎缩终于干涸的根本原因；4)屠中泽干涸后湖盆受西北强烈干燥气流及沙漠流沙的侵袭，迅速沙漠化．小片绿洲亦因弃耕、缺乏植物覆盖而沙化、消亡；5)沙漠中湖泊对改善滨湖生态环境的作用显著，但其蒸发渗漏损失水量也十分巨大，对于极为缺水的黄河流域而言，维持湖泊的存在并不一定合算．

Reconsideration of Environmental Evolution in the Northern Ulan Buh Desert in Historical Time

Based on the method of historical geography and combined the research results of modern hydrology,river,physiognomy and sed iment,the author gives some viewpoints on environmental changes in the northern U lan Buh Desert as follows.1) Northern Ulan Buh Desert in Pre-Qin Dynasty is ol d Tushenze lake,which area is much more bigger than from the Western Han dynasty to the Northern Wei dynasty;2) The lake shrank north and its area decreased t o 44 % of original size from the Western Han dynasty to the Northern Wei dynasty .The three countries of Yuhun,Linrong and Sanfeng founded in the Western Han dyn asty are on the oases by the rive r;3) Influenced by the geostrophic power,the right bank of Yellow River from Z hongtan to Xiecheng was eroded much,which was the only reason that the river cha nges its route to flow east. The Yellow River was also the only water source sup porting the Tushenze lake. So the route change of the river is the fundamental c au sation that led to the lake's atrophying and been dried up at last;4) After dr ied up,the Tushenze lake basin desertificated rapidly because it was invaded by desiccation airflow and quicksand. Some small Oases became desert for lacking plant cover or discarding cultivated land;5) Lake in desert has an evident eff ect on improving the surr ounding environment,while its evaporation and seepage is prodigious. So it is no t economical to maintain lake for the Yellow River area, which is short of water so much.