Study on Dynamic Changes of Wetland Landscape Pattern in Yellow River Delta

In this paper,the information about wetland landscape features of the Yellow River Delta in 1986, 1996,and 2006 were extracted respectively based on TM images and by support of Remote Sensing(RS)and Geographic Information System(GIS)techniques.By analyzing the information,we investigate the spatial and temporal changes of wetland landscape and explore the driving forces for wetland landscape pattern change in the Yellow River Delta within the past 20 years.Our results show that:(1)the area of man-constructed wetland demonstrated a sharp increase,whereas the proportion of natural wetland decreased accordingly.As an important part of the natural wetland,the tidal flat and Chinese tamarisk shrub wetlands in the Yellow River Delta has significantly shrank in coverage and degraded during the past two decades.(2)Since 1990s,some of the important landscape indices such as the number of patches,Shannon's diversity index,and Shannon's evenness index have increased.This indicates that the fragmentation degree of wetland landscape in the Yellow River Delta intensified, the type of landscape was much diversified,and each type is distributed uniformly in the wetland landscape and no dominant wetland landscape types can be recognized.(3)Landscape style transfer occurred between wetland and wetland,wetland and non-wetland.During the interval from 1986 to 2006 A.D,about 18.1%Reed meadow had been transferred to farmland,26.6%Seablite meadow transferred to salt pan and 11.9%Reed swamp transferred to Reed meadow.(4)The driving forces for wetland landscape pattern change analyses were conducted, and the result implies that both natural factors and anthropogenic factors have played important role in altering the pattern.The former includes decrease of discharge and sediment,self succession,while the latter mainly consists farmland reclamation,exploitation of tidal flat and oilfield development and construction.