气候变化和人类活动对塔里木盆地绿洲演化的影响

THE IMPACTS OF CLIMATE CHANGE AND HUMAN ACTIVITY ON EVOLUTION OF OASIS IN TARIM BASIN

通过对不同时间尺度下气候变化和人类活动对塔里木盆地绿洲形成与演化的影响分析。认为水文状况的变化是决定绿洲演化的首要因素，气候变化与人类活动也正是通过直接或间接地对绿洲水文状况产生影响而导致绿洲演化的。人类活动对绿洲演化的影响是局部的、阶段性的，而气候变化对绿洲演化的影响则是宏观的、连续性的。

The impacts of climate change and human activity on formation and evolution of oasis in Tarim Basin in different time scales were analyzed. Two opposite directions existed in evolution of oasis: the oasification and the desertification. The alternation of hydrological condition was the decisive factor on evolution of oasis. In different time scales climate change and human activity had different effects on evolution of oasis. The role of human activities on evolution of oasis was local and disconnected, while the impacts of climate change on evolution of it was macroscopic and continuous. It was indicated that from late Pleistocene the climate of Tarim Basin tended towards a severe aridity and the existence of oasis in Tarim Basin depended completely on the run off which was composed of melted glacier and snow and rainfall from mountains. The fluctuation of temperature in geologic period led to the altering of water amount of run off flowing to oasis. Therefore, the run off change caused by climate change in Tarim Basin was the decisive factor in geologic period on formation and evolution of oasis. The enhancement of thaw of glacier and snow and the increase of precipitation in mountains brought about an amelioration and improvement of the hydrological condition in plain and the oasification process predominated evidently in warm period. On the contrary, the reduction of thaw of glacier and snow and the decrease of precipitation led to a environmental deterioration . The area of oasis shrank and the area of desert expanded and the desertification process predominated in cold period. Although the social economic activity of human displayed a more and more significant effect as the continuous development of the human civilization, the climate change was still a major factor for the evolution of oasis in human history period. The socio economical condition in oasis appeared prosperous and the area of oasis extended comparatively when climate warming, but the desertification aggravated and the environment deteriorated when temperature lowering in the period of human history. As the development of civilization of human society, the impacts of transformation and destruction of human activity to oasis played a more and more significant role environmentally. The ancient artificial oasis moved from lower reaches to upper reaches in the river basin with the development of agriculture and the growth of population. On the other hand, the war launched by human in history caused a disastrous damage to oasis, which made the land ruined and river breached so that the oases were destroyed seriously. Undoubtedly, the development of oasis in Tarim Basin was dominantly influenced by human social economic activities in modern times. The population growth and the improvement of socio economic condition brought about the expansion of artificial oasis area rapidly with the reclamation of land and the shrinkage of natural oasis area consequently with the sandification and salinization in Tarim Basin. The desertification became the major obstacle for sustainable development of oasis in Tarim Basin.