| Land is the primary natural resource for human survival and reproduction owing to its production and nourishing function, carrying function and ecological service. Land cover means all the land surface elements including natural materials and man-made buildings, which biases towards the land natural attribute. Land use is long-term or periodic human activities according to the land characteristics by means of a series of biological and technical methods in order to achieve a certain economic or social purpose. However, with more and more land demand by human beings, soil erosion, forest degradation, land degradation, desertification, salinization and other environmental pollution phenomena are becoming increasingly serious, meanwhile human also begin to realize that land use and land change as a result are not only simple resource problems, but an important component of global environmental change and its vital reason. Therefore making research into the feedback of land use/cover change on human survival and sustainable development and human's response mechanism is quite significant in geography.Jianghan Plain is located in south central Hubei, which has the most freshwater lakes in the whole province. From the aspect of regional development strategy, Jianghan Plain is not only a part of Wuhan Urban Agglomeration in the east of Hubei province but belongs to "Yichang-Jingzhou-Jingmen" Urban Agglomeration in the west as well. In addition, Jianghan Plain is also an important part of Yangzi River Economic Belt, so Jianghan Plain has obvious advantage in location and great developing potential in the future. Because of the superior natural geographical condition and long period of agricultural exploitation, Jianghan Plain is the main agricultural production area, grain production area and marketable cotton production base. What is more, depending on the unique distribution characteristics of all the freshwater lakes and wetland, Jianghan Plain is the main wetland ecological area and an ecological barrier for Wuhan Urban Agglomeration, which plays a vital role in protecting the regional environmental quality and ecological security. Due to all the advantages mentioned above, Jianghan Plain becomes quite a special geographical region in China. Now it is subjected to intensive exploitation and utilization and different kinds of external interference, so making a study of the land use/cover change of Jianghan Plain to reveal the change tendency and characteristics of land types in this region, analyzing the factors that influence the landscape pattern of land cover, and evaluating the eco-environmental quality are not only a major field in geography but also have significant practical influence on promoting harmonious development of ecology, population and society.The article is divided into 8 chapters and the main contents are as follows:The first chapter is an introduction, mainly elaborating the research significance of the article. Through colleting and sorting abundant domestic and abroad research materials, including spatial-temporal evolution rule, driving forces, environmental effects, landscape pattern evolution and ecological assessment of land use/cover change, it collates the research progress of land use/cover change and its ecological effects. Meanwhile by summarizing all the related research achievements about Jianghan Plain, it finds out that the present study is analyzing the land use/cover change in just one certain aspect, while comprehensive and quantitative analysis of land use/cover change and its ecological security is quite little in Jianghan Plain since 21th century.The second chapter is the research program. On the basis of the previous study problems mentioned in the first chapter, the objective of this article is to enrich research on the last 20 years' evolution process of land use and ecological environment and the influencing factors and driving mechanism of landscape pattern in Jianghan Plain to help make reasonable use of land resources, deal with eco-environmental problems, plan and manage ecosystem, and put forward meaningful suggestions to make social economy and eco-environment develop harmoniously and sustainably. Furthermore, the chapter also states the research methods, technical line, study area and the study content that consists of the construction of comprehensive information database of land use/cover change, spatial-temporal change of land use/cover and multi-scale landscape pattern evolution from 1987 to 2010, gradient of landscape pattern in Jianghan Plain and its influencing factors, and land ecological security assessment in study area.The third chapter is about the construction of comprehensive information database of land use/cover change. It applies database technology and GIS to integrate quality and spatial distribution change, landscape pattern change, remote sensing images, digital elevation models, slope, slope aspect, land quality, meteorological statistics, population, economy and social development data of all land types'land use/cover in Jianghan Plain comprising 15 counties about 2823406 hectares in the year of 1987,1995,2000,2005 and 2010. The following content takes the database as foundation.The fourth chapter is the specific analysis of land use/cover spatial-temporal change in study area from 1987 to 2010. By adopting dynamic degree model, integrative index of land utilization, gravity model and land use transfer matrix to analyze the land quantity and spatial distribution change with time, it indicates that farmland is the main land type in the whole study area, most of the farmland's quality is quite good, water resources are considerably rich and that land is made full use. In the study period, there is great difference of quality change between various land types in different regions. From 1987 to 2010 the area of farmland decreases the most in study area, about 74589.51 hm2, and water area increases greatly, while the lake water tends to decline during these years. In the viewpoint of regional difference, land area changes greater in the east than in the west. In study area mutual transformation between farmland and waters is quite obvious and the area of farmland transformed into waters that are mainly ponds is the largest. In addition, the mutual transformation between farmland, waters and natural reserved land is frequent as well, and construction land is showing a rising trend all the time, which mainly comes from farmland and increases about 12995.62 hm2. At present, serious problems such as farmland greatly reducing, decreasing amount of farmland per person, high demand of construction land, prominent contradiction between land resources and population growth, land utilization efficiency yearly increasing, overload of land resources and ecological land continually declining, especially forest land, waters, natural reserved land bring huge pressure on the regional environment.The fifth chapter is about the multi-scale evolution of landscape pattern. By calculating plaque number, plaque density, average plaque area, area-weighted shape index and area-weighted patch fractal dimension of all types of landscape in study area and 10×10km grid, the result shows that rising plaque number and reducing plaque area of farmland lead to the increasing of plaque density and further irregular plaque shape, and all landscape indices of farmland change greater in the east and southeast than in the west of Jianghan Plain. Forest land, grassland and natural reserved land decrease gradually with time and unevenly distribute in study area, constantly retreating to the west and southwest, meanwhile plaque number reduces, average plaque area enlarges and plaque shape becomes more complex. The plaque number of waters rises, average plaque area declines, landscape fragmentation ascends, plaque shape becomes simpler and the spatial distribution of waters turns out to be continually uneven. The plaque number, average plaque area and plaque density of construction land rises yearly, and the plaque shape complexity increases as well.During the evolution process of landscape pattern in Jianghan Plain, Shannon's diversity index, Shannon's evenness index, contagion index and interspersion juxtaposition index respectively declines from 1.0139 to 0.9688,0.5570 to 0.5407,61.8750 to 60.1943 and 55.9097 to 55.4050. The result indicates that landscape diversity and landscape heterogeneity in Jianghan Plain declines under the influence of human beings, which disturbs the landscape connectivity between various land types greatly.The sixth chapter is the analysis of landscape pattern gradient and environmental effects. By applying RDA to analyze the landscape pattern gradient of six different land types and the whole study area, it comes to a conclusion that topography and geomorphology, climate, population, economic development and location all have an effect on landscape pattern evolution, and the lowest and highest explaining rate are 79.4%and 96.7%.For the majority of all land types, population density and gross domestic production play a prominent role in changing landscape pattern. The increase of the two factors will lead to a trend of landscape fragmentation of all land types except that the plaque area of construction land enlarges and plaque shape becomes further complex, meanwhile it also results in declining diversity and increasing unevenness of the whole landscape pattern. Average annual precipitation has an obviously positive effect on the average plaque area of waters, and the plaque area enlarges with more precipitation. Furthermore, under the influence of population growth and gross domestic production development, the increase of plaque number causes the expansion of waters.The seventh chapter is about the evolution of land ecological security and ecological protection measures. Based on the conclusion of chapter four, five and six, it analyzes the change of land quality and structure, evolution of landscape pattern and its effect on regional eco-environment in Jianghan Plain from 1987 to 2010. In addition, it also argues the factors that influence the regional land ecological security and has established a evaluation system from the perspectives of ecological capacity index, ecological stability index and ecological adaptability index to quantitatively evaluate the land ecological security on the scale of 10×10km. The result shows that the capacity of the whole land ecological system declines by 40.63 X 104ghm2, and the capacity per person has decreased from 1.17 ghm2 to 0.97 ghm2, which reflects that the area of land used for biological production is reducing and leads to the current situation. At the same time, the index of ecological stability decreases greatly, and the average stability index in each grid reduces from 0.72 to 0.52. The average adaptability index in each grid decreases from 0.56 to 0.41 and the maximum decrease is in the central south part. During the study period the average land ecological security index declines from 1.41 to 1.27, showing that the land ecological problem becomes even more serious. In addition, the increase variation of land ecological security index reveals the declining spatial correlation and rising spatial heterogeneity between each land types.On the basis of the conclusion above, the article divides Jianghan Plain into four function zones, namely optimizing zone of ecological city, comprehensive ecological development zone, ecological agricultural zone and control zone of ecological security, then proposes development strategy for each function zone to optimize the ways of resource allocation and utilization. For Jianghan Plain, it is of great importance to improve the ecological environment of rivers, lakes and wetland and strengthen ecological forestry construction to promote ecology, economy and society develop together. The eighth chapter is summary. The main conclusions and innovative points are summed up.
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