Analysis On Spatial And Temporal Evolution Of Habitat Quality In The Koshi River Basin Based On The Land Use/Cover Change

The research on the relationship between land use / cover change and ecological effect is a hot topic in the field of global environmental change.The study of habitat quality based on land use / cover change can provide scientific basis for the restoration and protection of ecological environment and sustainable development of the region.Based on MODIS NDVI time series data of 2000-2017 and land use type data of 2000,2010 and 2017,this paper takes the typical cross-border basin-Koshi River Basin as the research area.Based on the Arc GIS and the model of habitat Quality in the invest model,the spatial and temporal pattern of land cover change,land use degree,land use intensity,and habitat quality in the Koshi River Basin from 2000 to 2017 is quantitatively analyzed and its interrelationship is discussed.The main conclusions are as follows:(1)The spatiotemporal change of vegetation cover in Koshi River Basin was significant from 2000 to 2017.The average value of vegetation decreased from the middle to the South and North,and the growth of vegetation in the whole basin and each region gradually improved.The spatial differentiation of vegetation cover in the basin is obvious,and the overall trend is on the rise,among them,the growth rate in India is the largest and that in China is the smallest.More than 70% of the whole watershed has vegetation cover increasing trend,most of which are distributed in the central and southern parts of Nepal,most of India and southern part of China;The proportion of NDVI declining area is close to 20%,mainly concentrated in Kathmandu and its surrounding River Valley in Nepal,north central in China and the upstream of saptakoshi River in India.The correlation between vegetation and annual mean temperature is higher than that between vegetation and annual precipitation.(2)The degree and intensity of land use change significantly in Koshi River Basin from 2000 to 2017.During the study period,the area with weak utilization decreased first and then increased,but the area in 2017 was less than that in 2000;the area of strong utilization increased first and then decreased,which was larger in 2017 than in2000;this indicated that the land use degree in the basin generally showed a trend of continuous enhancement.In terms of spatial distribution,the land use degree is gradually strengthened from north to south,among which the land use and development degree in eastern India,central and Northern Nepal and central China is gradually weakened,However,the land use rate in central and southern Nepal and most parts of India remained at a high level.From the perspective of change process,the intensity and area of land use change in Koshi River Basin from 2010 to 2017 are higher than that of 2000-2010;in terms of type,the changes of unused land,construction land and water body in the basin are more active,and the changes of cultivated land and forest land are relatively gentle;at the level of conversion,the change intensity of cultivated land,grassland and unused land is high,among which the intensity of conversion from cultivated land to construction land and the intensity of conversion between grassland,water and unused land are high.(3)The annual mean of habitat quality in Nepal is the highest,and that in India is the lowest.In addition,the lower grade habitat quality is dominant in the basin.the overall distribution pattern of habitat quality is high in the middle and low in the South and North,which is consistent with the land use / cover distribution pattern in the Koshi River Basin.The degree of habitat degradation is low in the north and South and high in the middle,and the degree of habitat degradation is mainly mild in the degraded areas.The habitat quality change in 2000-2017 was mainly deteriorated and the trend was significant,and its change characteristics were closely related to land use change and vegetation change.The mean value of habitat quality and the grade of habitat quality of woodland and grassland were higher between 2000 and 2017,which played an important role in the maintenance of habitat quality;the areas where the habitat quality changes are mainly concentrated in the areas with high NDVI and rising vegetation cover.