Impact Of Land Use Change On Fractional Vegetation Cover In The Yangtze River Economic Belt

Fractional Vegetation Cover(FVC)is a basic characteristic indicator of land cover,reflecting the degree of vegetation growth.Land use change processes have an important influence on vegetation cover.It is of great theoretical significance to explore the changes in vegetation cover during different land use patterns and their transfer,in order to reveal the laws of human-land relationship and reconcile the conflicts between human and land.Over the past few decades,the ecological and environmental quality of the Yangtze River basin has shown a unique pattern of evolution and has been significantly disturbed by human activities.Taking the Yangtze River Economic Belt as the study area,the coupling study of land use and vegetation cover is of great practical significance for improving ecological and environmental management and promoting sustainable development.This paper takes the Yangtze River Economic Belt as the study area,and based on two remote sensing datasets,GIMMS NDVI and MODIS NDVI,and using methods such as the image dichotomous model and land-use transfer matrix,the change pattern of vegetation cover in the Yangtze River Economic Belt between 1982 and 2020 is studied;the characteristics of land-use change in the Yangtze River Economic Belt and the vegetation cover of different land-use types are analysed.The characteristics of land use change in the Yangtze River Economic Zone and the change characteristics of vegetation cover of different land use types were analysed;after the diagnosis of key processes of land use change,the impact of land use change on vegetation cover was analysed from two aspects of forest land construction and urbanisation respectively.The main findings and conclusions of this paper are as follows.(1)Between 1982 and 2020,the FVC of the Yangtze River Economic Zone rose from0.50 to 0.61,showing an obvious upward trend in stages.The four seasons of FVC in the Yangtze River Economic Zone differed significantly,all showing an upward trend in general,with growth rates of winter(3.66%/10a)> autumn(3.40%/10a)> summer(3.03%/10a)> spring(1.92%/10a).In terms of vegetation cover grading,the Yangtze River Economic Zone FVC has the highest proportion of moderate vegetation cover,ranging from 22.00% to 41.82%,followed by higher vegetation cover and the lowest proportion of low vegetation cover,ranging from5.11% to 6.94%.In terms of change trends,the Slope values of FVC in the Yangtze River Economic Zone between 1982 and 2020 ranged from-0.035 to 0.036,with a mean value of 0.0016,indicating an overall increasing trend.The area of the region showing an increasing trend of FVC accounts for about one-third of the total area of the Yangtze River Economic Belt,and the area of the region showing a decreasing trend of FVC accounts for 17.55% of the total area of the Yangtze River Economic Belt.The upstream and midstream areas of the Yangtze River Economic Belt mainly show an increasing trend in FVC,while the downstream areas mainly show a decreasing trend.(2)During the period from 1990 to 2020,the FVC of different land use patterns differed significantly.The average annual vegetation cover of cropland,grassland and forest land shows an increasing trend.The annual average FVC of cropland increased from0.47 in 2000 to 0.55 in 2020;the annual average FVC of forest land increased from 0.59 in1990 to 0.74 in 2020,an increase of 25.42%,and the annual average FVC of grassland increased from 0.44 in 1990 to 0.51 in 2020.the annual average vegetation cover of construction land showed a decreasing trend.In terms of the mutual transfer of different levels of FVC,the Yangtze River Economic Zone generally shows a trend of transferring low vegetation cover to high vegetation cover.Among them,the area transferred from lower vegetation cover to medium vegetation cover accounted for 10.65% of the total area transferred,and the area transferred from medium vegetation cover to higher vegetation cover was about 1/5 of the total area transferred.In terms of vegetation cover change in different land use patterns,forest land has the most obvious change in vegetation cover transfer among all types of land use patterns and dominates the vegetation cover change in the Yangtze River Economic Zone.between 1982 and 1990,the change in FVC of forest land accounted for the largest share of the transfer from moderate to high vegetation cover,accounting for about 6.87% of the forest land area.between 1990 and 2000 and From 2010 to 2020,the change in FVC on forested land was the largest shift from higher to higher vegetation cover,accounting for 6.20% of the forested area.In the whole study period,the largest proportion of FVC change in arable land was shifted from lower vegetation cover to medium vegetation cover.(3)The land use transfer process in the Yangtze River Economic Zone intensified the FVC change between 1982 and 2020.In terms of the probability of transfer of different land uses,the degree of transfer out of cultivated land is the most dramatic,with a total transfer probability of about 52.34% during the study period.The most pronounced transfer of land for construction was the most pronounced,with a total transfer probability of about39.27% during the study period.As the transfer out of cultivated land is mainly transformed into forest land and construction land,taking into account the transfer probability and the change in vegetation cover of different land use patterns,and after diagnostic identification,this paper concludes that the process of forest land construction and construction land expansion in the Yangtze River Economic Zone represents the impact of the land use transfer process on FVC.From the perspective of forest land transfer,FVC shows a clear upward trend in areas where other land use types are converted to forest land.In all time periods,the FVC in the areas where forest land has been transferred has increased to varying degrees,with the most significant increase in the FVC in the areas where forest land has been transferred between2001 and 2010,from 0.59 to 0.69.The above indicates that forest land transfer,led by forest land construction,has a positive effect on the increase in FVC in the Yangtze River Economic Zone,resulting in an FVC to an average increase of 4.75%.From the perspective of construction land transfer,the FVC in the construction land transfer area decreased from 0.48 to 0.45 between 1982 and 1990.between 1991 and 2000,the FVC in the construction land transfer area decreased from 0.46 to 0.44.between 2001 and 2010,the FVC in the construction land transfer area decreased from 0.44 to 0.33.Between 2011 and 2020,the FVC of the construction land transfer area decreased from0.34 to 0.32.The above shows that the urbanisation process-led construction land transfer has a negative effect on the enhancement of the FVC of the Yangtze River Economic Zone,resulting in an average decrease of 4.50% in the FVC between 1982 and 2020.