The Spatial and Temporal Variation of NDVI and Its Relationships to the Climatic Factors in Red River Basin

This paper studies the ecological effects of the "corridor-barrier" function of valleys and mountains to the spatial-temporal variation of NDVI and its relationships to the climatic factors in the Red River Basin by using GIS and Geostatistics methods based on the GIMMS data set from 1981~2006,SPOT VEG data in 2006 and the daily rainfall and temperature data of 42 meteorological stations in the basin from 1981~2001.The results show that:(1) The spatial autocorrelation degree of the vegetation index are significant variability in different direction,in generally,the distribution of the vegetation index are structurally influenced by the factors such as topography and the pattern of water and heat distribution,but the variability are found in different direction: under the "barrier" function of Ailao mountains,the Fractal dimension of the vegetation index in southwest-northeast and east-west direction are low,which means the spatial variability of vegetation index caused by random variability is less than that by structural variability;Under the "corridor" function of valleys,the Fractal dimension of the vegetation index in northwest-southeast and south-north direction are high,which means the spatial distribution of vegetation index is relative uniformity.(2) There exists the time lag effect that NDVI response to the rainfall and temperature changes,the range of the lag time is between 15~165 days,the NDVI response to the rainfall is faster than that to the temperature;under the "corridor-barrier" function of the valleys and mountains,the lag time and sensitivities of vegetation response to the temperature and rainfall has obviously spatial differences.(3)The vegetation of the Red River Basin does not have significant increased trends,but regional difference and spatial heterogeneity are obviously;66.77% of whole regional vegetation increased while 33.23% of that decreased,the change rate of annual NDVI is between-15.23%~23.16%.