| There were established many ancient capitals or cites in the middle reaches of Yellow River in history. These capitals were frequently moved originally by the changes of resources and environmental condition among the wide area of Guanzhong Plain and Yi-Luo Basin. However, many academicians always ignored this in their research based on the record in literature, but paid more attention to human factors, such as politics, economy, culture and military affairs in past. Actually, the changes of urban flourish, ruin and relocation are highly related to the changes of climate and environment. In present these studies still are few and simple. In paper has specially focused on systematically exploring the relationship between environmental changes and urban site changes, in the view of the relationship between nature and human and environmental change in ancient period in middle reaches of Yellow River, furthermore applied to scientific evidence combined with the record in literature and the data based on field work, and integrated the theories and methods in environment science and modern geography. There are very important theoretical meanings for adequately understanding the development regulation on relationship between environment and human, and the interaction between the urban site change and environment change in middle reaches of Yellow River. The study will offer some experience for meet the environmental and resource problem in urban development and construction process now, especially under global environmental change, and also provide the theoretical consult for environmental conservations in the middle reaches of Yellow River.The paper has analyzed the characteristics and processes of capitals or cities relocation and development in ancient period, and their influences by the change of resource and environment in the middle reaches of Yellow River in every historical stage. Also the paper has analyzed the reasons caused by environment change on plague and famine, selecting them as major of typical disaster occurring in the middle reaches of Yellow River, and their influences on urban development; analyzed the underground water pollution and its influence on urban development in ancient Xi'an city.Some conclusions were reached:1. The relocation and development of the ancient capital or city in history is originally influenced by climate changes in Middle Reaches of Yellow River even in east-Asian monsoon region, which could lead to regional natural resources improving or degenerating, even to control the spatial patterns of regional economic and society change. In that process, people always purpose to gain the more predominant environment and the more abundant water and land resources under the large scale of climate change by urban relocation. Also in which process they gradually make the most of environmental advantages and enrichment water and land resources, or avoid environmental disasters. And as being political, economy as well as military strength strengthen continuously, they have the more opportunities and initiatives to use those resources in large area. The selection of urban location was determinant by dissimilar factors in every historical stage with climate changes. So we grouped them into four types by the climate condition and the dominant factors. (1) Urban move by cold-dry climate and resource degradation. Under cold and dry climate, the biological resource and the water and land resources are degenerated. Those led to nomadic nationality in northern invaded to the farming nationality in southern. Seeking for better water and land resources, they moved their capitals or cities from high-latitude area to low-latitude, from northern to southern, from plateau to plain. (2) Urban move by warm-wet climate and flood. Climate is warm and moist; temperature has high, and rich of precipitation and water and land resources. But the flood risk increases in plain, the capitals or cities are moved from plant to plateau. (3) Urban move by arid climate and scarce resources. Climate is arid, shortage of water resource. Capitals or cities were moved from plateau to plain, in order to seek for better resources of water and land. (4) Urban move by unusual climate change and the more disaster. Climate has no obvious tendency, it is unusual to change, and environment worsen, disaster is occurring frequently. Cause to agricultural recession and city depression. To avoid disaster capitals or cities were moved to the superior environment.2. There were a total of nearly 140 times of plague occurred in recent 2000 years in the middle reaches of Yellow River, through statistical analysis through local historical disaster record and relating information. It shows that there has a significant relationship between the plague occurrences and the local climate changes and disasters. In the long term, the plague occurring are higher frequency in climatic deterioration period; particularly in period of unusual climate change, drought and flood occurring are most prone to plague; in season, spring and summer is plague-prone period. Moreover, citizen is most vulnerable by plague. So the plague occurrences had a great impact on local urban development in middle reaches of Yellow River. 3. Through analyzed on the reasons of famine occurred by environment change and the relation with city development, it shows that there has a significant relationship between the famine occurrences and the local climate changes, disasters and environmental conditions. Result follows: in cold climate period, crop yield is dropped and the frequency of famine occurring is higher; on the contrary, in warm climate period, it is lower. The serious disaster and deterioration of environmental condition often trigger famine in the historical period. 55% of famines was caused by drought in middle reaches of Yellow River. Famines occurring frequently have heavily affected urban development in past 2000 years.4. The underground water pollution occurred from Han Dynasty, and became more and more serious during historical period in ancient Xi'an city. Because the city is located in alluvial plain near Weihe River, and underground water flow though there, the down part of aquiclude is lower than the height of Weihe surface, those leads to underground water form a close circle,so easily make the contaminations enter in underground water and enrich. This becomes the primary reason of underground water pollution. Plenty of waste and excrement produced by large number of population and animals in history and being improperly deal with becomes the secondary causes. So in long historical period the under-ground water gradually deteriorated. This resulted in the change of urban location, the shortage of water resource and the retardarce of urban development in historical period. That also contributes to underground water pollution in Xi'an city today. Therefore, we must adequately take into account for the condition of terrain and hydrographic in solve water pollution in Xi'an city today.The paper has revealed the influences of resource and environment change on the relocation and development of these cities in the middle reaches of Yellow River; has put forward the type of ancient capital or city move and its characteristics ; has revealed the regulation of plague and famine occurring and its cause by environment change and the affect to urban development; and discovered the reason of underground water pollution and its mechanism caused by special terrain and water condition in Xi'an city. The scientific evidences from loess section and ice heart and so on, combines with the literature record, which indicating to ancient climate and environment change, were applied in study. This method is more rational because of both them confirming mutually. This study is helpful to profound understanding the interactive regulation between environment change and city development, promote to farther study in those field. Also this can offer the historical consult to solve the resource and environment problem in the course of city development, to coordinate the relationship between urban development and environment change nowadays.
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