Study On The Wetland Change And Its Influencing Factors In Northeast China During The Past Thirty Years

Although wetland only covers 6 percent of the earth, it can offer the living environment for 20 percent of the known species. Wetland is called as earth's kidney, and spoken highly owing to its ecology function, which can not be instead. The unique ecology function the wetland has is that it can not only supply food, row material and water resource, but also keep the balance of the ecology, the variety of species, the resource of the scarce creature. Furthermore, the wetland can reduce the pollution, supply the ground water, and control the soil corrosion.Northeast China is one of the regions where the wetland is the largest. Sanjiang Plain, Songliao Plain, Daxing'an Mountain range and Changbai Mountain develop quantities of wetland. Northeast China is called"grain marketing regulator","the biggest commodity grain strategy reserve base camp". So, the food security depends on the ecological environment health. However, what mentioned above pay a great price. For example, the contradiction between population development and land use resource is more and more predominant. Besides that, amount of wetland is reclaimed into cultivated land; water pollution is worse than before, the phenomenon of water resource shortage and waste is more serious. All of that make the wetland to be seriously interfered and damaged. Were it not be stopped, the biggest victims is our humanity itself.This paper, based on the RS and GIS technology, uses the MSS, ETM and CBERS data to analyze the present distribution and change rule of wetland in Northeast China. The variety rule is shown through the analysis of spatial-temporal dynamic change, dynamic degree, transfer matrix and landscape metrics. As we know, climate, terrain, and many economic factors have a great impact on wetland. So, the partial least-squares regression method is used to determine the importance of the influencing factors.The main results of this paper are as follow:1. During the thirty years, the total area of wetland reduced during 1975(total area is 86416.541km2) to 2000(total area is 63337.467km2), then increased in 2007(total area is 77860.753km2).(1) The costal wetland which is located only in the seaboard of Liaoning Province reduces continuously.(2) Lake wetland keeps on increasing. In the north of study area it is rarely distributed. On the contrary, the lake wetland is mainly located in the middle of Songliao Plain.(3) Marsh is reduced firstly then increased a little. From 1975 to 2000, the reduced marsh mainly distributes in the north of study area, Sanjiang Plain, middle and south of Songliao Plain. From 2000 to 2007, the increased marsh is located as long-narrow shape in the middle of the study area.(4) River wetland is reduced continuously, but in the later period, the range mitigates a little. From 1975 to 2000, the river wetland mainly reduces in Daqing City. From 2000 to 2007, the reduced area is in the west of the study area.(5) Man-made wetland accretes continuously. In the past thirty years, the area of increased man-made is the most. In the previous period, the increased area located in middle and east of the study area. Later, it is located in Sanjiang Plain, the middle and south of the Songliao Plain, southeast of the Jilin Province.2. The analysis of dynamic degree of marsh and man-made wetland shows that the minus value of marsh dynamic degree mostly overlaps on the high value of the man-made dynamic degree. It becomes apparent that part of the man-made wetland transforms from marsh.3. The transfer between marsh, man-made wetland and non-wetland is significantly. The increased man-made wetland is owing to the reduced marsh and non-wetland. During the previous period, marsh is used as man-made wetland and non-wetland. Later, increased marsh is benefit from non-wetland.4. The patch number of marsh increases continuously, its patch density increases first then reduces a little. The patch number and density of man-made wetland increases first then reduces. The Contagion Index shows that the agglomeration degree reduces first then increases. The Shannon's Diversity Index shows that the species diversity is less than before. Although the natural wetland turns to be well, the man-made wetland has already been the dominant landscape in Northeast China, the structure of landscape tends to be single, the influence of human activity is stronger than before. The ecological function need to be improved.5. From 1959 to 2008, the annual average temperature tends to rise up, the annual average precipitation tends to drop down. The climate pattern gradually changes from"cold-wet"to"warm-dry". During the fifty years, the annual average temperature increases from north to south, the annual average precipitation increases from northwest to southeast.Marsh and man-made wetland mainly locate in the middle value of CI and K. To be specific, the suitable distribution area for marsh is from -100℃month to -70℃month. Two types of wetland rarely locate in the semi-dry and high humidity area. The effect of CI and K'on the marsh is larger than man-made wetland. 6. The terrain in Northeast China is flat, and it becomes lower from west to east. The highest area is Changbai Mountain, its altitude is 2623m. The lowest one locates in the seaside which is in the north of the study area, its altitude is -277m. The altitude range which is from 0 to 100m is suitable for the development of costal wetland. For the other four wetland types the suitable altitude range is from 400 to 800m.7. The variety rule of population, habitation and GDP are basically the same. The area where the variety happened located in middle and south of the Liaoning Province, most part of Songliao Plain. In Sanjiang Plain, most part of Songliao Plain, the middle and west of Liaoning Province, the yield of grain increases.8. According to the PLS method, during 1975 to 2000 the most important influencing factor is annual average temperature, meanwhile, the least important one is habitation. In this period, the wetland change is mainly compliance with natural factors. During 2000 to 2007, the most important influencing factor is annual average temperature as well. The second influencing factors annual average precipitation is replaced by population. Thus, it can be seen that during 2000 to 2007 the impact of human factors are larger than natural ones.