| Based on the MODIS NDVI time series data from 2001 to 2016,the climate data in the same period mainly include monthly mean temperature,monthly mean precipitation and terrestrial ecosystem data in China,as well as carbon dioxide data set in China from 2010 to 2016,Arcgis Kriging interpolation method,linear trend analysis and correlation analysis.The temporal and spatial variations of NDVI in China over the past 16 years were analyzed to explore the relationship between NDVI and precipitation and temperature,the evolution of terrestrial ecosystem in China and the relationship between NDVI and carbon dioxide.The results show that:(1)The temporal and spatial distribution of NDVI: the vegetation belt increases gradually from north to south in spring and summer,and decreases gradually from south to North in autumn.There is no obvious seasonal change in Southeast China.The best season for vegetation is summer and autumn.From the spatial scale,the vegetation in China shows a trend of high in Southeast China,low in Northwest China and middle in the rest of China.Regional vegetation activities in China showed an upward trend,and NDVI increased significantly between 2001 and 2016.NDVI declined in 2005,2010 and 2012.(2)There is a good correlation between vegetation and climatic factors in seven zones of China.There is a positive and negative correlation between NDVI and temperature and precipitation in the zones.Except for North China and Central China,NDVI in other zones has a significant positive correlation with temperature,and there is a positive correlation between NDVI and precipitation in North China.(3)There is obvious lag between precipitation and vegetation growth,and the relationship between precipitation and vegetation is the highest.In terms of spatial relationship,precipitation in North China mainly affects the spatial distribution of NDVI.In South China,because precipitation and temperature are conducive to vegetation growth,the impact of climate is not strong.Vegetation is affected by both temperature and precipitation.(4)Since 2000-2016,except for a few years,the monthly average NDVI peaks appeared in August,most of the years NDVI peaks appeared in July,and the average NDVI in July 2011-2016 increased to more than 0.45 as a whole compared with the previous decade.(5)In the northwest of Urumqi,southeast of Qinghai,southern Lanzhou of Gansu Province,Xi'an of Shaanxi Province and south of Lhasa of Southwest of Tibet,vegetation growth is strong and weak.NDVI varies frequently in these areas,which is caused by vegetation types and geographical locations in these areas.(6)From 2010 to 2016,carbon dioxide in the whole region of China and all its districts increased,and the average annual carbon dioxide in the whole region of China rose by about 14.04 ppm in the past six years.There is a negative correlation between atmospheric carbon dioxide concentration and vegetation in China.There are obvious peaks and troughs in the variation of carbon dioxide concentration in a year.The highest occurs in April or May,and the lowest occurs in August.The results show that NDVI in China has shown an upward trend in the past 16 years.Vegetation and carbon dioxide in China have shown a negative correlation.Carbon dioxide concentration in China has shown an upward trend in the past 6 years.In this study,the spatial and temporal distribution of vegetation in China and the impacts of climate and land use types on NDVI,as well as planting in China,were analyzed with remote sensing technology and geographic information system technology.Based on the relationship between carbon dioxide and vegetation,this paper explores the impact of China's rapid vegetation development on vegetation since the 21 st century,provides scientific basis for agricultural production activities and urbanization construction in China,and supports China's rapid socio-economic development needs. |
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