The Study On Landscape Pattern Change And Ecological Risk Assmennt Of Yellow River Delta

The Yellow River delta is regarded as a new coastal wetland ecosystem.It plays an important role in adjusting the global climate change. The yellow river delta, with its unique geographical environment, which creates a suitable living environment for animals and plants, maintains the diversity of species as well as provides a well condition for the regional sustainable development. With the growing of population and the shortage of resources, more sources is founded by people from the wetland.However,the function of wetland cosystem is seriously damaged by a series of unreasonable economic ctivities,such as excessiving reclamation,excavating sand,exploiting oil resources,developing salt industries and aquaculture heavily.The area of the grass and the tidal flats is decreasing constantly. And the environment is polluted heavily.The quality of the ecological environment is declined. As the area of wetland reducing, the quality of sand and water declining, the diversity of biodiversity constantly cutting, it threats ecological security of the Yellow River delta area.The modern Yellow River deltat is selected as the study area in this paper,which is based on the vertex of Yuwa.Using the methods of based on the object-oriented interpretation and visual interpretation,the remote sensing images of Landsat TM in 1986,1996, 2006 and 2015 are interpreted,obtaining four landscape use maps.And using instantaneous water line method extracts the coastlines.Through analyzing the four vector maps in ARCGIS,the change of the area of landscape and the transfer of landscape type are founded.With the characteristics of modern Yellow River delta, some landscape indexes are selected reasonably,separately based on the patch level of landscape index and the overal landscape level.The dynamic changes of landscape pattern are analyzed. Using the comprehensive index of landscape ecological risk of predecessors and the Kringing spacial gridding method,the modern Yellow River delta ecological risk are analyzed in the spatial.The results show that:(1)From 1986 to 1986, the length of the coastlines of the modern Yellow River delta is on the decrease. But the land area of the modern Yellow River is increased by 10722.98 hm2.The change over the 10 years from 1986 to 1996 is the fastest.For nearly 30 years, the area of farmland, construction, waters, saline-alkali soil, salina, aquaculture water surface and other land are on the increase; the area of grass and tidal flats are on the reduce,which the grass is the most heavily, reduced by57107.35 hm2.(2)From 1986 to 2015, the characteristics of landscape pattern on the modern Yellow River delta are analyzed.From the transfer of landscape types, grassland is transformed into farmland.As near the ocean, the tidal flats are transformed into aquaculture water surface and salina and a small amount of saline-alkali soil.From the point of landscape index, landscape dominance is on the reduce, Landscape polymerization degree are on the increase.The landscape is given priority to the big patches.(3)From 1986 to 2015, ecological risk of the modern Yellow River delta are mainly composed of low and medium ecological risk,which is distributed in the inland.And both of the higher risk area and the high risk area are mainly distributed in the coastal zone, where the tidal flats and the grass is relatively richer and the water is more enough.The area of higher and the high ecological risk is the largest in 1996.According to the research results,human economic activities impact on the Yellow River delta wetland ecosystem.And suggestions for the protection of wetland ecological environment should be made.At the same time,the reasonable measures for protecting and developing wetlands should be made,which is conforming to the concept of scientific development and adapting to the requirements of modem times.