A GIS-based Study On Wetland Landscape Pattern Changes In Jianghan Plain

Wetlands, which serve important economic and ecological functions, is an important supporting system for the existence and development of human society. Due to human’s irrational exploitation of wetland resources, a series of ecological and environmental problems have appeared. Wetland landscape study has become a heated topic of several study areas, including geography, ecology, landscape and other science. Jianghan Plain is a typical wetland distribution area in China. Study on Wetland landscape pattern and evolution in the region not only has some practical significance for instructing rational exploitation of wetlands in this area, but also provides some reference for wetland study in other areas in China.With the support of RS, GIS techniques, based on multiple-temporal(1995,2000,2005and2010) Landsat TM images, combining topographic maps of different periods, statistical data, field sampling data and other documents, referring to some related theories and methods in different subjects, this paper designs a wetland taxonomy system which suits the spatial resolution of the TM images and extracts data from the images. Based on this, this paper uses landscape index method, dynamic degree model, relative change rate model and the transfer matrix method and combines some meteorological data, data in Statistical Yearbook of Hubei Province and other documents to analyze wetland landscape pattern change and its driving forces in Jianghan Plain. The conclusions are as follows:1, Wetland landscape in Jianghan Plain is mainly composed of rivers, lakes, reservoir and pond, marshes and tidal flats, which is mainly distributed in the southeast of Jianghan plain, concentrating in Honghu and Xiantao. From1995to2010, the total area of wetland landscape in Jianghan Plain increases, while the area of different wetland landscape changes in different scales. The area of Reservoirs and ponds landscape changes most significantly, which contributes to the increasing of total wetland area most greatly. The area of rivers, lakes and other wetland decreases in fluctuations, while the decreasing extent is low.2, The fragmentation characteristics of various wetland landscape are as follows:(1) The area of river landscape patches is large and its patches are usually strip with good continuity and low degree of fragmentation.(2) The number of reservoir and pond patches is the largest, the heterogeneity is high, the average area of these patches is small, the borders of these patches are complex, the fragmentation degree is high and the continuity is poor.(3) The shape of lake landscape patches is relatively regular with low fragmentation degree. During the study period, the maximum patch area of lake landscape increases, which indicates the fragmentation degree has decreased.(4)The number of marsh wetland patches is the least while their shape is the most regular and the fragmentation degree is low.(5) The shape index of tidal wetlands is slightly higher than that of marsh wetlands, but the index shows a tendency of increase, indicating that its borders become more complex. The average patch area and maximum patch area of tidal wetlands decrease and the fragmentation degree is high.3, Reservoirs and ponds, rivers, lakes account for the largest proportion of wetland landscape in Jianghan Plain. During the study period, the area of reservoir and pond wetlands increases and its landscape dominance enhances while the overall wetland landscape diversity decreases.4, Through analyzing the wetland landscape dynamic degree, and relative change rate and constructing transfer matrix in different periods, the author finds that the transfer between arable land and wetlands is the most frequent; the increasing area of wetlands mainly comes from arable land and also a little forests and construction land.During the study period, the dynamic degree of wetlands is positive and the change rate of wetland area during2000to2005is the largest.5, Base on meteorological data and other documents, from both the physical and human perspectives, the author analyzes the driving forces of wetland landscape evolution and find two reasons that contribute to the increasing of wetland area:(1) The precipitation during the study period is abundant and stable;(2) the policy of returning land to lake and other economic policies have been implemented.The creative thought of this paper is using a more detailed wetland classification system. Wetlands are divided into the types of rivers, lakes, reservoirs and ponds, beaches and swamps.This research is more detailed than previous studies and make a good use of image data advantage of TM.