Expansion Of Mountainous Cities And Urban Landscape Pattern Changes In The Langcang River Watershed

Urbanization,also known as urban or surburban sprawling,is the product of social and economic development at a certain historical stage and the result of human's transformation to the natural landscape.In 2016,China's urbanization rate reached 57.35%.Generally,the study of urbanization was concentrated in plain regions and relatively developed areas.And the urban development basically conformed to the model of concentric circles.China has enormous mountainous area,which covers two-thirds of total area.Specially,the mountainous area and the semi-mountainous area of Yunnan province accounts for 94%.Urban development in mountainous area is obviously dissimilar with plain's one.It is particularly important to probe urbanization model,and to reveal the processing dynamics and driving agents of mountainous cities.In this study,we selected three typical cities,Deqin County,Dali City and Jinghong City in Langcang river watershed,which are different in geomorphic and elevation above sea level.We surveyed its urban expansion and urban shape from 1990s to 2010s.Urban landscape pattern and urbanization development model were analyzed by land cover changes,pattern dynamics,and gradient change.At the same time,correlation analysis between the terrain features and expansion rate were conducted to understand physical contraints of landform on urban development.Main results were as follows:(1)The urban development of Deqin County conformed to fan pattern model.The urban development of Dali City and Jinghong City conformed to a fan pattern and multi-center model.The major urbanization in mountainous environment were the fan mode and multi-center mode.The urban development model was limited by terrain condition,and formed composite pattern.(2)Slope was the main factor to affect the distribution of construction land at Deqin County and Dali City.In 1990s,the roughness was the main factor influencing the distribution of construction land at Jinghong City,after 1990s,it changed to slope was.(3)The roughness was the decisive factor in the rate of urban expansion at Deqin County.There was no significant correlation between slope,the roughness and the urban expansion at Dali City.The expansion rate of Jinghong City was significantly correlated with slope and the roughness in 2000s-2010s.(4)Construction land at Deqin County increased from 1.26%to 6.98%,at Dali City and Jinghong City,it increased by 13.24%and 16.27%.Main transforming sources of construction land at Deqin County and Dali City were woodland and cultivate land,and at Jinghong City it were woodland,cultivate land and orchard land.The dominant landscape of deqin and Dali was still forest,but the proportion falled.At Jinghong,the dominant landscape type was transformed from woodland to orchard.(5)With the expansion of construction land,landscape fragmentation was increased.Because of increased large patches of orchard land and construction land,the fragmentation of Jinghong City was relatively low.With the expansion of urban,PLAND,LSI and COHESION of construction land increased.The urban landscape pattern was restricted by the terrain features,and it was also influenced by road construction,the protection of cultivated land,and the urban planning.