The Study Of Remote Sensing Dynamic Monitoring And Its Driving Mechanism Of Vegetation Cover In The Jinsha River Basin

Fraction of Vegetation Coverage(FVC)can reflect the status of regional surface vegetation coverage and is an important indicator for analyzing changes in regional ecological environment.Exploring its temporal and spatial distribution characteristics and the driving factors of spatial differentiation has become a current research hotspot in the field of geosciences.Located in the upper reaches of the Yangtze River,the Jinsha River Basin is rich in vegetation resources,but the watershed has serious soil erosion and the ecosystem is extremely fragile.Therefore,the study of the vegetation coverage in the basin and the influence mechanism of its spatial differentiation has important guiding significance for the restoration and improvement of the ecological environment in the basin.Based on this,this paper takes the Jinsha River basin as the study area,takes the MODIS NDVI data from 2001-2019 as the main data source,estimates the annual vegetation coverage and vegetation coverage in the four seasons of the year according to the pixel binary model,and used the coefficient of variation and trend analysis methods to reveal the spatial and temporal distribution and evolution characteristics of the vegetation coverage in the Jinsha River Basin in recent 19 years.In addition,combined with such as climate,terrain data in the study area,through quantitative geography detector model to explore the space-time differentiation of driving force factors of vegetation coverage.The following research conclusions are obtained:(1)The space-time distribution characteristics of vegetation cover: The average value of FVC in the Jinsha River Basin has fluctuated in the range of 0.662 to 0.687 in the past 19 years.The vegetation in the basin is mainly medium-high and high-coverage,which accounts for 70% of the total area.The FVC of the basin is low in the northwest and high in the southeast.Among them,the area with low vegetation cover is the most widely distributed in Sanjiangyuan area of Qinghai Province at the source of Jinsha River,while the area with medium and high vegetation cover is widely distributed in Changdu area of Tibet on the west side of the main stream of Jinsha River.Sichuan and Yunnan provinces,located in the middle and lower reaches of Jinsha River,have the best vegetation coverage,and the areas with high vegetation cover account for 24%and 20% of the total basin area,respectively.In the Jinsha River Basin,the areas with medium and high vegetation cover are dominant in summer and autumn,while the areas with low vegetation cover are most widely distributed in spring and winter.In addition,the vegetation coverage in areas with less topographic undulations in the Jinsha River Basin is generally higher,but the overall difference in vegetation coverage in different slope directions of the basin is relatively small.(2)The characteristics of space-time evolution of vegetation cover: the study area nearly 19 a vegetation cover is mainly stable,FVC non-significant change area accounted for 84.5% of the entire basin area,vegetation cover significantly increased area is mainly located in the north Yunnan and south Sichuan region,significantly and significantly reduced areas are mainly distributed in the southeastern county area of Qinghai Yushu County,Sichuan West Plateau County,and part of the urban area in northern Yunnan,its area accounts for 6.2%.The results of FVC change stability analysis show that vegetation cover in most areas of the basin is more concentrated and less volatile,but the vegetation cover in Qinghai Province and parts of The SichuanWest Plateau is more volatile,and the stability of vegetation cover is relatively weak in Lijiang,Dali,Kunming and other urban areas in northern and central Yunnan.The sustainability analysis of Hurst index shows that the proportion of area with positive and continuous change of FVC in the study area is 69.55 percent,and the vegetation activity in most areas will continue the trend of the past 19 a.FVC strong anti-persistent change area is mainly located in Qinghai Province,and scattered in west Sichuan,Changdu,Tibet and parts of northwest Yunnan,the future development trend of regional vegetation was extremely unstable and there were abrupt changes.(3)The comprehensive driving mechanism of the spatial differentiation of vegetation coverage: The factor driving force detection based on geographic detectors shows that the explanatory power of FVC spatial differentiation driving factors in the Jinsha River Basin is in the order of: climatic factors>non-climatic natural factors>human activity factors,of which climate division is the dominant factor affecting the spatial differentiation of FVC in the basin.The explanatory power of precipitation,air temperature and other climatic factors on the spatial differentiation of FVC fluctuated greatly in different years.The driving force factors for the spatial differentiation of FVC in summer and winter are significantly different.The summer climate factor has the strongest driving effect on FVC,but its fluctuation characteristics are more obvious.Vegetation activities weaken in winter,vegetation type and temperature play a major role in the spatial differentiation of FVC.The interactive detection results show that the two-factor enhancement effect of in the study area is obvious,and the interaction effect of any two factors on FVC was greater than the independent effect of the single factor.Among them,the interaction effect of vegetation type and sunshine duration on FVC was the most significant,and the spatial differentiation of FVC in Jinsha River Basin was the result of the interaction of multiple driving factors.