Land Use/Cover Change And Establishment Of Its Ecological Security Pattern In Typical Areas Of Yongding River Watershed

It is we11 known that LUCC(Land Use/Cover Change) is the current front and hot field of current global change study. It is an important cause that global environment changes, It has become the focus in the field of environmental research from home to abroad. Eco-environmental effects on land use/cover change will become a focus in this research field in the future. And regional ecological security has been paid more and more attention in ecological fragile areas. Mentougou watershed is the important region of Yongding River watershed in North China bio-diversity and ecological landscape reservation. It is very significant to research the change of land use and cover and its landscape ecological effects. Over the past few decades, land use changes there have brought forth a series of severe ecological and environmental problems, which directly threaten the sustainable development of local society and the ecological security, Employing several satellite images of Landsat-TM and the integrated techniques of RS, GIS, and GPS, the authors, taking Mentougou Basin as a case, studied the process and ecological effect of land use /cover changes since the beginning of 1984, and then established and evaluated its ecological Ecological Security Pattern based on land use types of 1984,1991,2005.The study results can provide necessary and helpful reference for sustainble development and ecological conservation.Applying the satellite images of Land sat-TM and the integrating techniques of RS, GIS, and GPS, the paper analyzes the processes and landscape ecological effects of land use /cover changes and constructs landscape ecological security pattern in the typical area of the Youngling River Basin from 1984-2005. The result shows that:1. Result indicated that the effect of organization of classification process is one of the important contents in land cover remote monitoring in mountain area, the iterative multi-stage classification approach was significantly (overall accuracy is 77.58%, Kappa value is 0.7194) better than the single-stage classification approach. And this organizational methodology for classification is feasible and reliable in the image classification of mountain area.2. Over the past 21 years, land covers in Mentougou Basin have experienced dramatic change.①In quantitative terms, from the year of 1984 to 1991, the absolute change extent obey the following sequence: broadleaved woodland >scrubland>mixed woodland >grassland> conifer woodland>cultivated land> rural residential land >Industrial- mineral land >Urban land>others land>water area; from 1991 to 2001,grass land> shrub woodland > rural residential land > mixed woodland > conifer woodland > Urban land > cultivated land > Industrial- mineral land > broadleaved woodland >others land > water area;and from 2001 to 2005, rural residential land > shrub woodland > conifer woodland > broadleaved woodland > mixed woodland > urban land > industrial- mineral land > grass land > others land > water area > cultivated land。②There is difference in direction and intensity of land cover. The over forest woodland kept on expanding over the past 21 years , the cultivated land decreased in 1984,1991 and 2001 and then increased after 2001,the percentage of it in the study area is respectively 4.20%, 3.09%, 1.91% and 2.06%; The industrial- mineral land and urban land experienced an obvious increase, the percentage of which in the study area increased from (1.99%,0.8%) to( 2.74%,3.23&)in 1984 and 2005. Other lands experienced considerable decrease in 1984 and 1991, but increase after 2001. From the year of 1984 through 2005, The area of water area increased from 1984 (0.7% )to 1991(0.77% )and decreased in 2001,2005, respectively, the percentage of it in the whole study area is 0.24%, 0.45%.Meanwhile, land-use/cover change (LUCC) models have been playing process and quantitatively analyzing the status and the dynamic change of land use degree in research area. The land use/cover spatial pattern of each type was also very different. Index of average elevation and average gradient of land cover type were calculated, spatial distribution characters of each land cover type was analyzed in study area from 1984 to 2005.3. Based on the GIS and landscape indices model,ecological environment effect that the regional land cover change produced in study period was analyzed with landscape metrics on both class and landscape level from 1984 to 2005. On the whole landscape, there was a decrease in the patch number from 1988 to 2005,the patch number decreased from 35350 in 1984 to 25413 in 2005. The who1e shape turned regular and the fragment trend of the landscape degree became weaken from 1984 to 2005. Forest and shrub types are the main components of the present vegetation in the study area. The area of different landscape elements was very uneven. There were a decrease of the patch number and patch density to the total area. The patch number and patch density of industrial- mineral land and urban land increased obviously. The center of gravity of the each class landscape occurred distinct spatial movement in different study periods; the landscape ecological Value Index (LEVI) of the whole study area grown upon from 3710.27 to 3733.59,and the general eco-environmental quality tended to be better.4. Applying landscape ecological theory and effective cost distance model (EDM) constructed landscape ecological security pattern, which can realize the actual conditions of ecological security during different periods for case study. The temporal and spatial change of the ecological security caused the change of landscape structure during the period from 1984 to 2005. The distribution of ecological security rank is the obviously highest in the western mountain area and the lowest in east plain. The percentage of low security area in the study area is respectively 9.49%,10.44% and 9.30% in 1984,1991 and 2005; Finally, according to the present ecological security state, low security region should firstly be restored.By making a systematic study on the pattern and processed, ecological assessment of land use/cover change, also establishing and evaluating its ecological Ecological Security Pattern in Mentougou Basin, the author have made the following progresses:1.Taking Mentougou Basin in typical area of Yongding River watershed as example, the author systematically studied he processes and landscape ecological effects of land use /cover changes and constructed landscape ecological security pattern over the past 21 years, which fills up the gap of LUCC regional cases in Mentougou areas, and provided a kind of new approach for understanding and solving such challenging ecological and environmental problems.2. New methods have been proposed in this paper to improve the classification accuracy in addition to unsupevised and supervised classification procedures. the iterative multi-stage classification decreased influence of terrain. The gross classification accuracy of these new methods is 77.58 %, which is higher than the common unsupevised and supervised classification method. And this organizational methodology for classification is feasible and reliable in mountain area image classification.3. Landform factors influence land cover and its spatial distribution obviously. Index of average elevation and index of average gradient of land cover type were calculated and analysised. The center of gravity of the each class landscape occurred distinct spatial movement in different study periods. Study demonstrates that the LEVI put forward in the paper can well describe the ecological effect of land cover change on regional scale,which makes the index systems more perfect.