关键词: 气候变化, 农牧过渡带, 历史时期

Abstract: The farming-pastoral transitional zone in northern China is an active geographic phenomenon in historical times. It not only shows the occupational alternation between farmers of the Han nationality and herders of minority nationalities, but also reveals the shifting of combined terrain sharp in economy and culture. The transition zone is based on the climatic condition in terms of the natural background, and reflects the social-economic patterns in a special natural condition of semi-humid zone to arid zone. It has to change its terrain sharp when the climate shifts. After all, the farming-pastoral transitional zone results from the interaction of natural condition with human society, and is affected by a number of elements from the two sides. This paper examines four cases in historical period, which happened in the process of climate dropping to cold and dry, and tries to analyze what come up in the transitional zone with climatic changes. The emperor of Northern Wei Dynasty, Xiaowendi, moved his capital southward from Pingcheng to Luoyang in A.D.493. The prosperous agricultural area surrounding the capital came down. Documentary evidences show that a continual drought from A.D.486~493 and cold, e.g. frost in July, were the main driving force to the decision-making of moving capital. The Horqin Sandy Land was an active agricultural region during the control times of Liao Dynasty, the 10th ~11th centuries. When N zhen nationality defeated the Liao Dynasty in the beginning of the 12th century, the agricultural area was totally given up. The desertification was serious at least in part of Horqin sandy area. No solid evidence of social side can explain the farming abandoned phenomenon which was resulted from an excessive reclamation. Considering the temperature dropped down in the beginning of the 12th century, it can be believed that the climatic change was the main force to result in the farming abandoned phenomenon. In the beginning of the 14th century the climate turned to cold. The main effects beyond the farming-pastoral transitional zone were the calamitous snowstorms. Numerous herders got away from their clans, and moved southward as refugees. The Yuan government spent lots of money and foodstuff to relieve them. The three Wuliangha tribes moved southward in the early decades of the 15th century. It induced a conflict between the shifting tribes and Ming Dynasty along the Great Wall. Evidence shows such war was based on the climatic change, because the three tribes had to find a new surviving room. The four cases happened in the same condition of climatic changes, but the changes of farming-pastoral transitional zone diverged in respective styles. It can be concluded that: 1) the climatic changes have impact on the shift of the farming-pastoral transitional zone; 2) the effects of impact come forth through a given social system, though in the same base of climatic condition; 3) the climatic changes can act as a trigger, which lights up a war, when the farming nationality confront with herding one along the transitional zone.

Key words: climatic change, farming-pastoral transition zone, historical period