VEGETATION COVERAGE CHANGE BASED ON NDVI AND ITS RELATIONSHIP WITH CLIMATE FACTORS IN CHONGQING

The relationships between vegetation and climate are always an important domain in ecological research.NDVI((Normalized Difference Vegetation Index)is a effective index that reflects the vegetation change.In recent years,the relationships between NDVI and climatic factors have been studied in many papers and the relative conclusions were different.Chongqing include the most part of Three Gorges Reservoir Area.In these area,vegetation cover are various,and the eco-environment is relatively fragile.Therefore,it is worth to study the features of vegetation cover and the relations between vegetation and climate.In this paper,MODIS-NDVI dataset was combined with climatic dataset to analyze vegetation cover changes and the correlation with climate factors in the study area during the periods of 2000-2011.NDVI images came from NASA,the spatial resolution was 250m,which were treated with cloud checkout,atmosphere rectification and maximum value composite every 16 days.Climate indices included monthly average precipitation,monthly average atmospheric temperature,yearly average atmospheric temperature,yearly average precipitation obtained from 34 weather stations in Chongqing.The correlation coefficients of NDVI with all climatic factors were calculated with SPSS.The results showed that the annual average NDVI of Chongqing was on the rise,but some differences existed in time and space scales in the 12 years.Judging from the spatial scale,the NDVI growth areas were mainly located in the northeast,southeast,southwest region.The NDVI lower areas were mainly located in metropolitan area,county city,the Yangtze River and Three Gorges Reservoir area.Judging from the time scale,the NDVI had some growth in spring and autumn,and was very stable in summer,but declined in winter.The correlation of NDVI with temperature and precipitation was not significant in the interannual scales,while the temperature and precipitation showed a significant correlation in the month scale,and the correlation with temperature was greater than precipitation.