Study On The Influence Of Climate Factors And Different Substrates On The Change Of NDVI Of Vegetation In Southwest China

Global climate change is not only a climate issue,but also an environmental and development issue.The ecological and environmental problems caused by global climate change have damaged terrestrial ecosystems.As an important component of terrestrial ecosystems,vegetation is sensitive to climate change and is an indicator of ecological and environmental changes,and the study of the interrelationship between vegetation and climate change has become one of the important contents of research under global climate change.Southwest China is a typical climate change sensitive area and ecological environment fragile area in China.Under the background of global climate change,the study on the spatial and temporal change characteristics of its vegetation cover and the influence of factors can provide a reference basis for how to solve the ecological environment problems in southwest China.Based on this,this paper uses MODIS NDVI data,combined with DEM,precipitation,temperature,landscape type and soil type data,and adopts the methods of one-dimensional linear regression trend analysis,partial correlation analysis,multiple regression analysis,correlation analysis,lagged correlation coefficient and geographic probe to investigate the spatial and temporal changes of vegetation cover in southwest China(Sichuan,Chongqing,Guizhou and Yunnan)from 2001 to 2020.The spatial and temporal changes of NDVI and the driving forces were studied,and the following findings were obtained.(1)The NDVI of vegetation in Southwest China from 2001 to 2020 showed an increasing trend at different time scales,with the largest increase rate of 0.048/10 a in the spring;the overall spatial distribution of the mean NDVI of vegetation in Southwest China was low in the northwest and high in the southeast,and low in the northeast and high in the southwest;the spatial variation trend of its vegetation NDVI generally showed that the area with an increasing trend was larger than the area with a decreasing trend.The area with decreasing trend of NDVI of vegetation in the summer accounts for 15.31% of the area of the study area,and its area proportion is larger than that of other seasons and years.(2)In terms of regional characteristics,the mean value of vegetation NDVI in the slope 6-15° area is the highest,and the area with an increasing trend of vegetation NDVI is the largest;the mean value of vegetation NDVI in the high-altitude hilly area and the area with an increasing trend of vegetation NDVI are higher than those in other landscape types;the mean value of vegetation NDVI in the Iron and bauxite area is larger than that in other soil types,but the change of vegetation NDVI in the drained soil area is obvious.The NDVI of vegetation in this area has the largest proportion of both increasing and decreasing trends.(3)Vegetation in the Sichuan basin is mainly influenced by precipitation,while vegetation in Guizhou and Yunnan is more sensitive to changes in temperature than precipitation,and in general,vegetation in southwest China is mainly influenced by temperature;the response of vegetation NDVI to precipitation and temperature in southwest China has regional differences,with different lag times in different regions,and the lag period is between 0 and 3 months.The lag effect of vegetation NDVI on precipitation and air temperature response in different slope subdivisions shows similar performance,and there are differences in the lag time of vegetation NDVI on precipitation and air temperature response in different geomorphological type zones and soil type zones;when the vegetation NDVI of different substrata is affected by precipitation and air temperature synergistically,the vegetation NDVI is affected by air temperature more than precipitation.(4)The determining power of climate factors and different substrates on the spatial distribution of vegetation NDVI is as follows:temperature > soil type > precipitation > slope > landform type,and temperature is the main factor affecting the change of vegetation cover in southwest China;the effect of factors alone on the spatial distribution of vegetation NDVI is smaller than the synergistic effect of multiple factors on vegetation,and the synergistic effect of temperature and other factors on the change of vegetation cover in southwest China is larger than the synergistic effect of other two factors.is greater than the synergistic effect of other two factors;the range of annual precipitation suitable for vegetation growth behaves differently in different years,which is related to the temperature,except that the cumulative temperature is in the range of >231.92 ?,the slope is between 6-15°,the landform type is high-altitude hills,and the soil type is iron-aluminous soil and iron-rich soil,the vegetation growth and development in Southwest China is better and the vegetation cover is higher.In the past 20 years,the annual average precipitation of suitable vegetation growth in Southwest China was >526.52 mm,and the annual average temperature was in the range of6.17-12.36°C.The range or types of other factors were the same as those in separate years.