A Study On The Environmental Changes Of The Ancient Lou-lan Oasis From The Han To The Jin Dynasty (2～(nd) Century B. C-the End Of 4～(th) Century A.D)

Lou-lan site had been found for one hundred years. Many researchers have paid more attention to it and made a great progress in geography,history and archaeology, etc. Nowadays, the environmental evolution of Lou-lan is a focus of studyBased upon a careful analysis and integration of all past scientific investigations and researches, especially on the study of Lou-lan documents which were written on wood tablets or papers, the present thesis is an argument and discussion on the environmental evolution of ancient Lou-lan oasis. The main conclusions can be summed up as follows:(1) It was a windy and extremely arid climate and annual precipitation is scant and sporadic. Moreover, the natural vegetation was very sparse and mainly composed of drought-resistant and salt-tolerant shrubs and perennial grasses. So, the physical condition of the ancient Lou-lan Oasis was unfavorable for agricultural development.(2) Lou-lan Road, which was through the ancient Lou-lan oasis, was the only course that linked the West and the East during the Western Han dynasty and again during the Wei-Jin-Qianliang period (221A.D-367A.D), but was nearly neglected during the Eastern Han dynasty.(3) Before the first century B.C, local inhabitants practised nomadism,fishing and hunting. At 77 B.C, Chinese soldiers and emigrants began to reclaim farmland in the ancient Lou-lan oasis. But it was a long standstill period for the reclamation in the ancient oasis from 221 A.Dto 376 A.D and the large-scale agricultural reclamation brought adverse impacts such as salinization and desertification on the fragile, extremely arid environment.(4) Before the mid-fourth century A.D, the lower Tarim River combined with the Konqi He at Qiongke and formed the Tarim-Konqi River which then flowed eastward into the old Lop Nur Atter then a reach of water apart from the Tarim-Konqi River flowed southeastward near the present Yin-pan site and formed a new tributary which called Zhu-bing He. Finally, the Tbrim-Konqi River changed its channel and turned southeastward too in the end of fourth century A.D. AS a result,the ancient Lou-Ian oasis turned into desert.The ancient Lou-lan oasis was one of the most typical oases"in the world.lt has been evolved chiefly through the interplay of the natural factors, such as the extremely arid climate, the changes of Tarim-konqi River channel in natural condition and so on, and the human activities, such as the rise and fall of agricultural reclamation, the changes of its traffic statue, etc.