Analysis on the dynamic evolution of spatial pattern of the lake wetland landscapes in Yinchuan city.

Regional ecological security is the foundation for sustainable development,and the lake wetlands are of vital importance for maintaining regional ecological security.In this paper,the dynamic evolution of the lake wetlands in Yinchuan is analyzed using landscape pattern index based on 3S technology.The results are as follows:(1) The characteristic values,such as the total,average and maximum areas of the lake wetland landscapes in Yinchuan,are in a gradual reduction trend since recent 20 years;(2) The internal hierarchical structure of the lake wetlands in Yinchuan is improved in some aspects,but the overall hierarchical structure is still fragile and unstable,for example,some characteristic indexes,such as the,FD and FS,were obviously better in 2004 than that in 1997,but there were still some gaps compared with that in 1987;(3) The driving forces resulting in the dynamic evolution of the lake wetland landscapes in Yinchuan include both the natural and artificial factors,such as the climate change,hydrological process,population growth,agricultural development activities and policy change,in which the artificial factors are dominant.According to the conclusions,some measures and suggestions are put forward,which can be referred in the ecological construction and the maintenance of ecological security in Yinchuan.