The Extraction And Inversion Study On The Vegetation Of Xianghai Wetland By Remote Sensing Composite Index Method

The restoration of the wetland ecosystem has gradually become an important issue in the field of ecological environment protection. The purpose of this study is to improve the management of the large-scale Northeast wetlands, to enhance management efficiency and to grasp the causes and trend of changes of the wetlands, therefore, remote sensing composite index method was used to distinguish and evaluate the wetland plant communities.The research zone of this study is the reeds area of the core region in Xianghai Nature Reserve of Jilin Province, adopting remote sensing composite index method often used in environmental remote sensing studies which classify after coupling imaging the normalized difference vegetation index(NDVI), normalized difference water index(NDWI) and normalized difference soil index(NDSI). The vegetation of this area is extracted for one single year inversion and for years inversion, does the statistics of changes in the area of different classifications, and the wet and dry transition in space.The single year inversion examines classified images mainly through supervised classification and field investigation of the satellite images in 2010, determines the reliability of the method consequently. The land use map of Xianghai Nature Reserve is collected and classifies the main forms of land use based on the land type. After the synthetic images are generated, the vegetation prediction map is generated according to ground surface classification by adopting the supervised classification method. In order to test the accuracy of the method, a field survey is carried out in the corresponding time of satellite images, and uses the Kappa coefficients to determine the range of confidence. The inversion results show that the Kappa coefficient of remote sensing composite index method adopted in this study is 0.632, which is in a high degree of confidence.The years inversion classified the images of different years applying the same supervised classification group on the basis of the single year inversion, and obtained the changes of different land use types in the corresponding period. The results of the years inversion show that compared to the reed landscape in 1999, the reed area began to decline in fluctuations after 2000. After entering 2000, the area of reed began to dry, in the year of 2002 and 2007, the area was almost disappeared, Although there were signs of recovery after 2009, the area had not reached the level of 1999 in the year 2010.The reed had experienced the degradation firstly and recovery gradually. Compared the land use types between 1999 and 2010, the area of dry reed region was greater than the wet region as a whole.The study of remote sensing composite index method can provide effective reference data for the protection and restoration of the Xianghai Wetland, it is beneficial to improve the monitoring efficiency to the plants in the Xianghai Wetland, and to find out the feature regions to carry out reasonable repair and management.