Investigating Vegetation Greenness Variatio Along Altitudes In Qinghai-Tibetan Plateau Based On Satellite Remote Sensing

Qinghai Tibet Plateau is an important part of the terrestrial ecosystem,global climate changes have an important effect on vegetation greenness variatio on the Tibetan Plateau.What is the impact of climate change on vegetation in the Tibetan plateau? Does the change in altitude affect the growth rate of vegetation? How do different terrains affect the growth and distribution of vegetation? NDVI is a significant reference in the study of vegetation greenness variation.Based on Landsat and MODIS satellite remote sensing data,the change of vegetation green degree in different altitudes of the Qinghai Tibet Plateau is analyzed.We have used a variety of statistical analysis methods of spatiotemporal data to carry out scientific research and analysis on several major problems we need to solve,and have drawn the following main conclusions:(1)Vegetation at different altitudes in the Qinghai Tibet Plateau has different characteristics in the growth process.We divided the NDVI data of winter and summer in the study area according to different altitudes,and made relevant statistics respectively.Although the vegetation growth in winter and summer showed a good development trend,there were some differences in different seasons and altitudes.In winter,the area with NDVI greater than 0.3 has been expanded by about 50%,while in summer,the expanded area is only 5-10%.In winter,the higher the altitude is,the faster the vegetation grows.The interannual change rate of low altitude is close to zero.With the elevation rising steadily,the interannual change rate generally exceeds 0.003 after the altitude exceeds 5000 m,and even reaches 0.005 in some areas,which is the opposite in summer.The movement speed of NDVI isoline with the change of altitude has the same characteristics in winter and summer.The highest moving speed of NDVI isoline in low altitude area is 15-30 m/year,and that in high altitude area is-10~-20 m/year.(2)Topography and altitude have different effects on vegetation growth in winter and summer.In summer,NDVI decreased from 0.7-0.5 at the highest to 0.3-0.1 after the slope was more than 40 ° with the increase of slope,which was opposite in winter.The NDVI isoline velocity in summer and winter will increase from 20 m / year to more than 60 m / year with the increase of slope,and the greater the slope,the more obvious the difference between different directions.The velocity of NDVI isoline in Yangpo area is more concentrated than that in yinpo area.(3)Although the change of topography will have a very important impact on the growth of vegetation,the climate condition is still one of the main factors of vegetation growth.The sensitivity of the northern part of the Qinghai Tibet Plateau to temperature and precipitation is mostly within ±150 m / ?,and the southern part is between ±300 m / ?.The sensitivity of the southern part is greater.The increase of slope will also increase the sensitivity of vegetation to temperature by 3-5 times,and the direction difference of vegetation in these areas is also obvious,the direction to the South and the direction to the north are very different.