Gradient analysis of landscape spatial and temporal pattern changes in Beijing metropolitan area

The gradient based landscape metrics analysis is now widely used to study the landscape pattern changes in respond to the urbanization.In order to discover the trend of spatio-temporal changes in Beijing metropolitan area during the past 15 years,several landscape metrics are computed using a moving window along a 96 km long transect across Beijing metropolitan area from west to east.Specially,the spatial extent of sub-landscape,which is determined by the moving window’s size,is profoundly examined.The results show that the metrics varies smoothly and regularly along the selected transect when the window size is greater than 6 km×6 km,and irregularly fluctuated for the smaller window size,that the spatial and temporal landscape characteristics of Beijing city match the hypothetical framework of spatio-temporal urban sprawl in the form of alternating processes of diffusion and coalescence well,and that some new trends of the urban sprawl style in Beijing metropolitan area,such as leap-frog manner,are also detected by the gradient landscape analysis.