Analysis Of Vegetation Changes And Its Influential Factors In The Three-river Headerwater Region Based On NDVI

As the largest Natural Reserve in China,The Three-River Headerwater Region 's unique natural environment has bred a wide variety of vegetation and animals,rich wetlands and swamps play an important role in maintaining the ecological and water balance of the area.Because the ecological environment of The Three-River Headerwater Region is extremely sensitive and fragile,it is of great significance to study the change rule of the vegetation in this area for the rational development of local resources and to maintain the ecological stability of The Three-River Headerwater Region.Based on MODIS data,this paper uses the normalized vegetation index provided by the MOD13Q1 to calculate the NDVI from 2000 to2015 in TRHR,and analyzed the growth and change of vegetation in space and time series.With the help of statistical method,the relationship between the factors affecting the vegetation development and the NDVI is analyzed,and the trend of vegetation change and the important factors affecting its change are finally obtained.The main results are as follows:(1)The maximum vegetation index of TRHR has increased rapidly from May and reached the maximum value in July,and it is larger from June to September as a whole,showing a single peak form fluctuation.(2)NDVI varied from 2000 to 2015,and it increased slightly in general.(3)In the three districts,the vegetation in the source area of the Yangtze River is the worst.There is little difference between the Yellow River Headwater Region and the Lancang river Headwater Region.The growth of the Yellow River Headwater Region's vegetation is slightly better than that of the Lancang river Headwater Region's.(4)From 2000 to 2015,the vegetation in most areas of TRHR showed basically unchanged and slight improvement,and there was less serious degradation and obvious improvement.(5)The vegetation coverage of the TRHR is good,the bare soil occupies less area,is concentrated in the west of the study,and the high coverage area is located in the eastern and southern areas of the study.Vegetation coverage is better in the east than in the west,and better in the South than in the north.(6)Research shows that rainfall has little effect on vegetation in the area,and air temperature is an important factor affecting vegetation development.(7)The vegetation development is best when the height of the study area is about 3800 meters.The vegetation development is best between 30 and 40 slope degrees,and the vegetation development on the north slope is better than the south slope.(8)The change of soil water content is consistent with that of NDVI.and it is an impact factor for vegetation development.