河西走廊汉唐古绿洲沙漠化的调查研究

AN INVESTIGATION AND STUDY ON THE DESERTIFI CATION OF THE ANCIENT OASES FROM HAN TO TANG DYNASTIES IN THE HEXI CORRIDOR

运用考古学、历史地理学的方法，实地调查了河西走廊汉唐古绿洲１０大片沙漠化区域，其总面积约４７００多ｋｍ２。揭示了这些古绿洲沙漠化区域的若干特征，简要探讨了其形成的过程和机制。

Using the methods of archaeology and historical geography, the author investigated the desertification regions of the ancient oases from Han to Tang Dynasties in the Hexi Corridor in Gansu, Brought to light several features of the desertification regions, and studied the processes and causes of desertification in the ancient oases. 1. The desertification regions in ancient oases. There are 10 pieces altogether: the Western Sandy Land in Minqing County (the lower reaches of Shiyang Rivey), the Juhuadi in Minle County, the Heishuiguo in Zhangye City (the middle reaches of Heihe River), the ancient Juyan Oasis (The lower reaches of Heihe River), the lower reaches of Maying River and Bailang River, the Eastern Sandy Land of Jinta County (the lower reaches of Northern Big River), the Bijiatan in Yumen City, the western border district of alluvial fan of Changma River, the lower reaches of Lucaoguo River, and the ancient oasis of Yangguan Pass in Dunhuang City. Their total area is about 4 700 km 2. 2. There are several features in the desertification regions: (1) The majority of these regions are situated in the lower reaches of rivers. In these regions the water resources are relatively poor, and the effects of natural calamities (for example drought, windstorm) are relatively serious and frequent. Moreover the regions are distributed alternately among drift sand, gobi and alkali flat, even are surrounded by desert. Thus the latent instability of ecology environment in the regions is very strong. As a result, the processes of desertification are easy to be aroused and activated in the regions. Influenced by makind's unreasonable fashions of land exploitation, the oases are easy to evolve into deserts. For this reason, the major areas of the prevention and harnessing of desertification should follow with interest at the lower reaches of the rivers. (2) The regions were eroded seriously by wind. The main landscape in the regions is the ancient cultivated land that was wind eroded alternating with scrub dunes. Furthermore a lot of the ruins of ancient cities were left over the regions, for example Souyang City in Anxi, Camel City in Gaotai, Shazhou City ad shouchang City in Dunhuang, Juyan City in Ejina Banner, Liancheng City in Minqin, Heishui City in Zhangye, Xigu City in Jinta, Bijiatan City in Yumen, etc. These ruins of ancient cities are the most authoritarian historical specimens of our country's ancient civilization and a culture of long standing on the Silk Road. The Hexi Corridor is one of the areas where the ruins of ancient cities are the richest in quantity, the most diverse in type, the most integrated in dynasties, and most complete in preservation in the world. In the light of these ruins of ancient cities and their historical relics, we can restore the flourishing appearance of the ancient oases in those days, and can bring to light the occurrence periods and the causes of the desertification. 3. The occurrence periods of the desertification processes in the ancient oases were as follow: some districts were in the later period of the Han Dynasty, and the greater number of districts were in the later period of the Tang Dynasty (some districts lasted to the Yuan Dynasty). The main cause of the desertification processes in the ancient oases was as a result of artificial cause, that was closely related to the political and military situation, the state of agricultural and stock raising development, the use of water resources, and the level of man's knowing natural environment in ancient times; but there were natural causes as well (mainly the changes of climate in aridity and humidity in history). The author pointed out yet that although the some ancient oases evolved into deserts, yet the total area of Hexi Oases was not reduced, it had displayed to a great extent a sort of oases transferance.