Abstract: Urbanization is an important social and economic phenomenon. Since the 20th century, global urbanization has presented unprecedented scale and speed, especially in China. Spatiotemporal patterns of urban expansion, the salient features of urbanization process, have caused attention of Chinese government as well as scholars at home and abroad in different disciplines. The development mode of new-type urbanization in China is gradually changing, emphasizing the intensive and efficient development of urban lands, reflecting a change in thinking from the blind pursuit of rapid urbanization to high-quality development. According to the unbalanced regional development of China, promoting new-type urbanization needs to be suited to local conditions according to the different development characteristics of eastern, central and western regions, to allocate land resources rationally and efficiently, to realize intensive cluster development according to the timing, thus promoting urbanization transferring from land-oriented urbanization to human-oriented new-type urbanization. Existing academic research has revealed differences among the eastern, central and western regions. However, study on geographical space of urbanization process is relatively lacking. On the other hand, study on spatiotemporal urban expansion patterns has focused on the comprehensive technology integration such as Remote Sensing (RS) and Geographic Information System (GIS) in spatiotemporal analysis of built-up land expansion. To date, comparative study of urban expansion for different regions is rare, most of which has put more attention on demographic urbanization than physical urbanization. Therefore, the comparative study of urban expansion for cities of similar scale deserves more attention. Based on the content of new urbanization and the "T" mode development strategy, we made a comparative study of urban expansion between three central cities along the Yangtze River (i.e., Nanjing, Wuhan and Chongqing) with RS data covering four time periods during 1980-2010, integrating GIS techniques and landscape ecology approaches. Indexes of urban expansion intensity, urban expansion types, urban expansion elasticity and some landscape metrics were used to quantify urban expansion characteristics and to cover the internal mechanisms. Results showed that: (1) During 1980-2010, urban expansion intensity obviously increased and showed a tendency of Nanjing > Wuhan > Chongqing; while the increasing rate of urban expansion intensity ranked as Chongqing > Wuhan > Nanjing since 2000. (2) For the urban expansion types, edge-expansion always played a dominant role in Nanjing; outlying and edge-expansion dominated Wuhan with 2000 as a divide; edge-expansion accounted for the largest area of Chongqing, but the outlying growth increased rapidly after 2000. (3) Dynamics of urban expansion elasticity suggested that urban expansion fell behind population urbanization in eastern China, while central and western China presented an inverse situation after 2000. (4) Landscape analysis corroborated that RS, GIS and landscape ecology approaches combined to uncover patterns and dynamics of urban expansion.

Key words: new-type urbanization, eastern, land use, urban expansion, RS and GIS, landscape Index, Yangtze River