Abstract:

Since the 1990s,the city of Beijing has entered into a centrifugal acentric phase of suburbanization,and the expansion of construction land in Beijing mountainous area will take up an important position.So study on the expansion of construction land is of great significance.Some indexes were created to indicate the expansion of construction land,such as the growth intensity index,the relative growth rate,etc.and they have their(unique) advantages and disadvantages.To overcome their shortcomings and make the expansion differentiate among different districts in Beijing mountainous area notably,we put forward the growth degree index along with the above two indexes to depict the spatial differentiation of construction land expansion comprehensively. Based on the land use shift data and land use change data,these indexes in three successive phasesi.e.,from 1993 to 1996,1996 to 1999 and 1999 to 2002 respectively,were calculated and the characteristics and spatial difference of land use expansion of different construction land types were analyzed.The results indicated that since the 1990s,the suburbanization has been extending to the outer suburbs,and great changes have taken place in Beijing mountainous area,the expansion degree became increasingly great.And the spatial expansion of construction land has the characteristics of both difference and abnormity, which expanded everywhere taking irregular expansion as the characteristics and suburbanization here was still in an initial phase.At the same time,the expansion has an outwards trend.Also because of the restriction of natural conditions and the orientated function of different districts,the regional spatial difference is evident.We hold that with the maturity of pole-axis system,the process of suburbanization in Beijing mountainous area will be entering a more active phase.Relevant measures should be taken to direct the expansion to a move active way.

Key words: construction land expansion, spatial differentiation, Beijing mountainous area, growth degree index