The Research On Dynamic Change And Driving Force Of Wetland In Yanchi County, Ningxia Province

Wetland is known as the cradle of the earth, as having unique ecological functions, containing a huge ecological benefits and economic benefits. This paper takes the wetlands in Ningxia province as the object, exploring the dynamic change of wetland in recent20years, analyzing the impact on vegetation diversity and stability, finding out the driving forces, combined the remote sensing image of Land sat5TM from the year of1988,1994,2003,2010and2013with the field investigation. The result shows that:①The wetlands area of Yanchi and the surroundings was12311.95ha,14903.48ha,20464.57ha,14129.67ha, and15019.95ha from the year of1988,1994,2003,2010and2013. The area of wetland shows that, overall in2003as the turning point, it raised at first and then decreased.②The number of patches of wetlands of Yanchi and the surroundings was49,39,36,41and42from the year of1988,1994,2003,2010and2013. And the patch density was0.398,0.262,0.176,0.290,0.280n/km2.The number and density of patches shows that, overall in2003as the turning point, it decreased at first and then raised. To some extent, it can reflect the degree of landscape fragmentation and structure complexity drop before they rise.③The existing wetland area is volatile, transforming between grassland and wetland mainly between1988a and2013a, but less with forest land and farmland.④Wetland vegetation community diversity and stability is closely related to the change of the wetland area. In the process of wetland area is reduced or increased, wetland vegetation community diversity and stability are reduced. When the wetland area is stable, the wetland vegetation community diversity and stability increased.⑤Through the analysis, we can see that the nature was the fundamental driving force that resulted in the change of wetland area, mainly is rainfall evaporation and temperature. Meanwhile the human driving force on the wetland had biphasic effects. Such as the rangeland close and grain for green project increase the wetland area, while grazing without permission and artificial lake with groundwaterc shrinkage the wetland.