Temporal And Spatial Evolution Of NDVI In Qinghai Lake Basin And Its Relationship With Environmental Factors

Vegetation is one of the important components of the surface ecosystem.The temporal and spatial variation of vegetation NDVI can reflect the variation characteristics of vegetation cover.The Qinghai Lake Basin is located in the northeastern part of the Qinghai-Tibet Plateau.The vegetation types in the basin are diverse,the terrain is diverse,the ecological environment is fragile,and the ecological status is very significant,which is very sensitive to global climate change.In this paper,the Qinghai Lake Basin is used as the research area.Using the MODIS-NDVI image data of the Qinghai Lake Basin from 2000 to 2016,combined with meteorological data and DEM data in the basin,using remote sensing and GIS techniques,mathematical statistics and geostatistics,etc.The relationship between the temporal and spatial variation characteristics of vegetation NDVI and environmental factors in the lake basin was studied,and the following main conclusions were drawn:(1)The NDVI distribution in the Qinghai Lake Basin has strong spatial variability,and the NDVI mean increases gradually from the northwest to the southeast.The NDVI value changed in a single peak during the year,and the single peak period was from July to September.The vegetation growth was the most lucrative in August and the lowest in February.The overall NDVI of vegetation in 2000-2016 is on the rise.(2)The spatial distribution of vegetation NDVI in the Qinghai Lake Basin is obvious.With the cyclical changes in the seasons,the coverage of the vegetation cover in the Qinghai Lake Basin moves between the northwest and the southeast.The interannual variability of vegetation NDVI is obvious,and the overall appearance is: “the south and north are weak,the northwest is strong,and the high and low volatility coexist”.(3)The trend of climate warming and humidification in Qinghai Lake Basin from 2000 to 2016 is obvious.The annual average NDVI coexisted with positive and negative climatic factors,but the annual average NDVI changes did not significantly respond to the interannual variability of climatic factors.The monthly average NDVI is positively correlated with temperature,precipitation,and relative humidity,and has a significant response to changes in climatic factors during the year.(4)There was a significant positive correlation between NDVI and precipitation in the grassland of Qinghai Lake.Precipitation was the dominant factor affecting the growth of alfalfa grassland.The NDVI of Kobresia meadow and Kobresia meadow was not significantly positively correlated with temperature and precipitation.There was a significant positive correlation between NDVI and precipitation in the purple-flowered grassland.(5)Within the grading range of elevation and slope of Qinghai Lake Basin,the variation trend of vegetation NDVI and vegetation NDVI is obvious.Altitude and slope are important factors affecting the spatial distribution difference of vegetation NDVI in Qinghai Lake Basin.In contrast,the aspect of the slope is not an important topographic factor that affects the spatial distribution of vegetation NDVI in the Qinghai Lake Basin.