| The ecological environment provides guarantee for the sustainable development of human life,production and social economy.Evaluating of the Countyal ecological environment is not only the basis for reasonable planning,but also an effective way to understand the ecological environment in the County.With the increasingly severe global environmental problems,the study on the changes of "land use" and ecological environment has become a flash point and research trend at this stage.In recent years,RS and GIS technologies have developed rapidly and have powerful functions in data acquisition,processing and expression.Therefore,combining RS and GIS technologies to comprehensively evaluate the ecological environment status of the study area,Objective and comprehensive dynamic monitoring and analysis of Countyal ecological environment changes and discussion of land use type change laws can provide a scientific basis for relevant local government departments to carry out ecological environment quality assessment and ecological reconstruction planning decisions.Jiuzhaigou County is located in the plateau area of western Sichuan,which belongs to the Aba Tibetan and Qiang Autonomous Prefecture.It is located in the transition zone between the Sichuan Basin and the Qinghai-Tibet Plateau,and has a complex geological structure background.The County has vertical and horizontal river valleys,high terrain in the northwest and southwest,low terrain in the southeast,stepped terrain.It belongs to a plateau humid climate and has the Jiuzhaigou Scenic zone,a world natural heritage.In this study,Jiuzhaigou County was used as the research area,based on RS and GIS technology,combined with the remotely sensed data of Landsat 8 with a spatial resolution of 30 m in three periods in 2014,2016,and 2018,study the changes of ecological environment in Jiuzhaigou County,and evaluate and analyze the results.Supervise and classify the remote sensing images during the three periods in the research area to obtain the information of land use types and the dynamic transfer of various areas.Using remote sensing data and topographic data as the main data sources,construct an ecological environment evaluation index system suitable for Jiuzhaigou County.The analytic hierarchy process was used to determine the weighting coefficients of the participating indicators.The grid unit was used as the evaluation unit of this study to obtain the evaluation index of ecological environment in Jiuzhaigou County,and the spatial distribution map of the ecological environment of Jiuzhaigou County was drawn.While analyzing the temporal and spatial dynamic changes trend of the ecological environment in Jiuzhaigou County,and the analysis of factors of driving force combined with human and economic data and meteorological data,the main results of study are as follows:(1)Remote sensing images can be used to obtain the information of land use types in three periods through support vector machine technology under supervised classification,and the classification results are verified by combining with field samples to obtain confusion matrix.The overall accuracy of land use classification is above 80%,and the classification effect is better when Kappa coefficient is greater than 0.8.Combined with the "land use transfer matrix",the specific changes of area transfer of different land use types during the study period were analyzed.(2)Based on the index of ecological environment(EI)and remote sensing ecological index(RSEI),some indexes retrieved by remote sensing are added,some indexes that are difficult to obtain are removed,and an appropriate ecological environment evaluation index system of Jiuzhaigou County was constructed.(3)The remote sensing images of the three periods are taken as the main data sources of evaluation indexes,and remote sensing inversion includes a series of indexes such as surface temperature,soil erosion index,vegetation coverage,water body index,etc.DEM and slope factor can be obtained by combining thematic data.Relying on the standard layer of topography and nature and seven indexes,a comprehensive evaluation model of Jiuzhaigou County's ecological environment is constructed based on the analytic hierarchy process.(4)Use the analytic hierarchy process to acquire the weight of each evaluation index,standardize the evaluation index factors,and use the comprehensive evaluation model to obtain the Jiuzhaigou County ecological environment evaluation index.Using the method of natural discontinuity to classify the ecological environment evaluation index,the spatial distribution pattern of the ecological environment grade of Jiuzhaigou County is obtained.The evaluation results showed that the average value of the ecological environment evaluation index of Jiuzhaigou County in three periods fluctuated around 0.5,and the ecological environment grades were mainly distributed between Grade I and Grade III.Among them:the total area of Grade I and Grade III accounted for more than half of the total area of the research area;The distribution of Grade II and Grade III is similar in the three periods,and the corresponding areas are in a stable state.The average value of the evaluation index decreased from 2014 to 2016,and by 2018,the value has increased and gradually returned to the same level as 2014.Judging from the distribution of each level,they are distribute's alternated,the proportions are different,and the same time the proportion of each level is also in a dynamic change.From the perspective of spatial distribution,the areas with worse ecological environment are mainly distributed in the northwest and southwest areas with high altitude and low vegetation coverage,while the areas with well ecological environment are mainly concentrated in the southwest area and on both sides of the river basin.(5)Combined with the annual average temperature,annual precipitation,population,GDP data,etc.,the factors of driving fore causing ecological environment changes are analyzed from natural and human factors,and it was found that precipitation and temperature have have a certain impact on the changes in the driving force of the ecological environment. |
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