Changes of Chinese Beginning Date of Vegetation Greenness Period Based on NOAA NDVI
基于NOAA NDVI的中国植被绿度始期变化

Beginning date of greenness period of vegetation(BGP)is closely related to seasonal dynamics of the lower atmosphere and is therefore an important variable in influences and feed-back mechanisms of global climate variation to terrestrial ecosystem.Detecting BGP using remote-ly sensed data at regional or global scales has become an advanced topic in geography and ecolo-gy.Based on the processed NOAA/AVHRR NDVI data,the study is to use Logistic fitting model on cumulative frequency of NDVI to compute BGP of China by pixels from 1982 to 1999,count the annual average BGP of every vegetation type and bio-climate district,and analyze the inter-annual change trends,spatio-temporal dynamic change feature of BGP of various spatial types.The results indicate that:(1)BGP have an advance trend in most regions and obviously advance in North China Plain,northeast Guizhou,the middle and south Hunan,west Guangxi and typical grassland area of east Inner Mongolia.(2)The regions in which inter-annual fluctuation of BGP are over 10 days are mainly distributed in the area covered with agricultural vegetation types,the areas covered with evergreen vegetation types and the areas covered with steppe vegetation types.Thereinto,the fluctuation of BGP in Hetao plain,Guanzhong basin,east Henan,west Sichuan basin,Guangdong,Taiwan and so on,are over 15 days.(3)BGPs of the other vegetation types ex-cept temperate desert show an advance trends.(4)With the reduction of annual accumulative tem-perature and increase of drought indices,BGP of various bio-climate areas delay.An advance of BGP is found in South China,East China,Central China,North China,Inner Mongolia,Northeast China and Tibet,whereas a delay occurred in Shaanxi,Shanxi and Northwest China.(5)BGP of all vegetation types evidently delay in 1982,1983 or 1984,which may be associated with the strong EI-Nino effect in the 1982-1983 period.