Research On Wetland Landscape Change In Wuhan City Based On 3S Technology

As a special ecological system which is between the aquatic ecosystems and terrestrial ecosystems, wetlands boasts several functions such as regulating the climate, controlling soil erosion,promoting deposition of land reclamation,degradating pollutants and beautifying landscape, thus being known as "kidney of the earth" which brings great ecological, economic and social functions and benefits to the world at large. With the continuous awareness improvement of human being, the whole world has paid great attention to the wetlands on its uniqueness and importance to the ecological environment, which has enabled wetland patterns study became one of the highlights in the current wetland researches domain. Located on the junction of Yangtze River and Han River, Wuhan City, the biggest city in central China, enjoys the typical terrain features such as rivers, lakes and wetlands. With the accelerating process of urban circle and urbanization, Wuhan City have witnessed the sharp decline in its wetland area and biodiversity and witnessed the deterioration in its urban functions. Therefore, efforts of analyzing the wetland landscape changes and carrying out predication search on wetlands in Wuhan City will be of significance to the environmental rehabilitation and to rational exploitation, protection and utilization of wetland resources in Wuhan City.This paper is subsidized by National Key Technology R&D Program in the 11th Five year Plan of China (2006BAC08B03) that'Study of Forest Ecosystems and Changes of Iternal Structure.This thesis has taken Wuhan City as its research area through 3S technology. It has analysed the wetland landscapes pattern changes in Wuhan City in the recent twenty years by using the Landsat-TM images in year 1991 as well as in 2003, and CBERS02B-CCD images of year 2009 as its data source, and by extracting wetlands information through the method of multi-scale image segmentation and visual interpretation. When the analysis of driving factors in wetland landscape changes and prediction research on wetlands are done, strategies on wetland management and protection have been presented. The major study results are listed below.(1) Best practice combined operation has been carried out to the remote sensing images through the joint entropy method and the method of best index Results are listed as follow. Images reaches the maximum information amount and rich colors when the 4,5,3-band of Landsat-TM images and 4,3,2-band of CBERS-02B images are combined, which improves the extraction of wetlands information.(2) In line with the national wetland classification system formulated in National Survey and Monitoring Technical Regulation of Wetland Resources which is issued in year 1997, and according to the local status of wetlands in Wuhan City, the author of this thesis classified the wetlands in Wuhan into four categories, namely, river wetland, lake wetland, marsh wetland and artificial wetland.Due to the limitation of factors such as the smallest polygons which can be distinguished by the remote images and potentially artificial interpretation of constraints,the wetland study area is divided into six categories such as beaches, lakes, paddy fields,library pond, rivers,swamps by the author of this thesis.(3) Wetland data of Wuhan City have been extracted by jointly using the method of multi-scale image segmentation and visual interpretation. Data accuracy in these three year (1991,2003,2009) has exceeded 80% and met the requirements of remote sensing image precision in medium-resolution.(4) Quantitative analysis on the changes of Wuhan's wetland landscape features through landscape pattern index and dynamic change models. Results show that wetland area in Wuhan City firstly declined but then increased slowly from year 1991 to 2009. It also demonstrated that natural wetland area has been on a downward trend, while the artificial wetlands showed a gradual upward trend. Wetland landscape patches and the overall wetland landscape fragmentation in Wuhan City have increased, which shows that big gaps exist in these wetlands and that they are scattered with each passing day. Matrix landscape type of overall landscape shifted from natural wetland to paddy field, one type of artificial wetland, from year 1991 to 2003. Meanwhile, matrix landscape type of overall landscape included paddy fields and pond wetlands both of which belonged to the artificial wetlands.After analyzing the regional differences of wetland landscapes, author of this thesis noticed that landscape type changes of the surrounding plain areas which took urban Wuhan as its center, namely, Caidian district, Jiangxia district vary greater than that of Wuhan City. He also recognized that the landscape type change of wetlands including Huangpo, Xinzhou, Hannan and the hills which are next to Wuhan is greater than that of Wuhan City.(5) Analysis of the landscape pattern change leads to the fact that the wetland landscape change are formulated by the main driving factors including topography, climate,population explosion, urban circle construction, economic factors,policy factors.(6) Markov model is used to predict the wetland landscape changes of the research areas in the future. In Wuhan City, the wetland landscape area of year 2010 is 10.07km2 larger than that of year 2009, while that of year 2011 will be deducted when it is compared to year 2010. The deduction area did not vary much, demonstrating that the wetland landscape in Wuhan tends to be stable.(7) Management strategies and protection suggestions have been given out to Wuhan City according to its wetland landscape change eatures and its development trend as well as its problems, such as, serious water pollution, intensifying wetland landscape fragmentation and deterioration of wetland landscape environment. Strategies and suggestions are listed as:accelerating the formulation of local regulations on wetland protection, arduously enforcing the wetlands regulations and protection, saving no efforts to spread advocacy and education on wetlands protection, carrying out the overall study and planing on wetland resources, exploiting and utilizing the wetlands in a rational way (wetlands reclamation, developing the wetland natural reservation areas and wetland parks, establishing wetland database and management system in Wuhan according to the wetland classifications, increasing funds input to wetlands protection). All these are done with the hope of providing the decision-makers from relevant departments with scientific basis.