Temporal And Spatial Changes Of Landscape Biodiversity In The Yeerjing River Basin

In recent years,with the continuous impact of climate change and human activities,the ecosystem and biodiversity of the river basin have been severely damaged.The Yerqiang River Basin is located in the upper reaches of the Tarim River in Xinjiang,and is an important area for landscape biodiversity protection in the Tarim Basin.Therefore,accurately grasping the characteristics of the changes in the landscape biodiversity of the Yerqiang River Basin is of great significance for protecting and restoring the ecological environment of the Yerqiang River Basin and ensuring the smooth implementation of the“Belt and Road”ecological civilization construction.Based on the data of land use in 1990,2000,2010 and 2017,this paper takes the Yerqiang River Basin as a research area,and uses mathematical statistical models and landscape indexes to analyze the characteristics of the landscape change and the evolutionary law of landscape pattern of the watershed landscape.In order to explore the temporal and spatial characteristics of landscape biodiversity in the Yerqiang River Basin,This study is based on the meteorological and NDVI data for the three phases of 2000,2010 and 2017,Select the habitat quality of the watershed,the net initial productivity of vegetation(NPP)and the landscape structure index to construct a biodiversity evaluation index system at the watershed landscape level,To analyze the spatial-temporal distribution pattern of river basin landscape biodiversity from 2000 to 2017,The study of the spatial and temporal distribution pattern of biodiversity aims to provide a theoretical basis and reference for the monitoring and protection of landscape biodiversity in the Yerqiang River Basin.The main conclusions of this study are as follows:(1)From 1990 to 2017,Significant changes have taken place in the landscape area and dynamics of the Yerqiang River Basin.In terms of landscape area changes,the largest increase in cultivated and bare land areas are 4496km~2 and 4156km~2,respectively,and the grassland area decreases the most,reaching13628km~2.To analyze the change characteristics of landscape type dynamics,the single landscape dynamics of construction land is much larger than other landscape types,reaching 54.56%per year,followed by waters,wetlands and arable land.From 1990 to 2000,the integrated landscape dynamics of the river basin are the most dynamic.(2)The number of patches in the overall landscape of the Yerqiang River Basin has increased year by year,the degree of patch aggregation decreases,the shape of the patches becomes more complex,and the degree of fragmentation in the river basin continues to increase.Variation characteristics of river basins on the landscape category scale:the shape of patches in each landscape type has become more complex,and the degree of aggregation has decreased.the number and density of patches in each landscape type have increased to varying degrees,of which the number of patches on grassland and bare land has the largest increase and the degree of fragmentation is greatest;The maximum patch index has increased,reflecting the spatial expansion characteristics of semi-artificial and artificial landscapes;(3)The change characteristics of the maximum value of the landscape structure state index show a decreasing-increasing-decreasing trend,which indicates that the overall fragmentation of the river basin landscape has become more intense.The patch shape has become more complex,and is more vulnerable.The overall structure of the landscape is unstable.In terms of spatial distribution,the areas with relatively high landscape structure index(landscape structure stability)are mainly distributed in the forest and grassland area in the Kunlun Mountains and in the middle of the water and the natural vegetation areas on both sides of the river channel downstream.The areas with relatively low landscape structure index(poor landscape structure stability)are mainly distributed in cities and cultivated areas where human activities are intensive,as well as bare lands on both sides of the lower reaches of the water and glaciers/snowy areas on the upper reaches of the water.(4)From 2000 to 2017,the habitat quality of the Yerqiang River Basin generally showed an upward trend.In terms of spatial distribution,the spatial distribution pattern of habitat quality in theYerqiang River Basin dose not change much during the study period.The high-value areas of the basin's habitat quality are mainly distributed in the forest and grassland areas in the middle of the basin of the Kunlun Mountains,and areas of natural vegetation that are distributed around the periphery of the lower reaches of the river.The median area of habitat quality in the basin is mainly distributed in the developed agricultural areas in the lower reaches of the basin.The low-value areas of the basin's habitat quality are mainly distributed in the plateau mountains in the south and southwest,with an average elevation above 3000m in the upper reaches of the basin,as well as bare lands and deserts on both sides of the lower reaches of the basin.(5)From 2000 to 2017,the variation characteristics of the total initial net productivity and average value of vegetation in the Yerqiang River Basin both showed a trend of increasing first and then decreasing.The high-value areas of the NPP in the water are mainly distributed on the sloping plains and flood plains on the front of the mountain where agricultural activities are more frequent,and distributes in the forest and grassland areas of the Kunlun Mountains in the upper reaches of the watershed.The NPP value of the Yerqiang River Basin is generally low,and most of the NPP values are mainly derived from agricultural crops under human economic activities.(6)From 2000 to 2017,the landscape biodiversity of the Yerqiang River Basin generally showed an upward trend,but the proportion of the low value area in each period is above 78%,indicating that the protection of the landscape biodiversity in the river basin is still severe.Spatially,the distribution pattern of landscape biodiversity in the Yerqiang River Basin is similar to the distribution of habitat quality in the basin.The increased areas of landscape biodiversity in the river basin are mainly distributed in the hilly areas in the middle of the river basin of the Kunlun Mountains,and a few peripheral areas distribute on both sides of the downstream river channels.These areas are mainly high-school mountain forest areas with grass irrigation and transition areas for agriculture,animal husbandry and natural forest reserves etc.The areas with reduced landscape biodiversity are mainly distributed on both sides of rivers in the lower reaches of the basin,and a few plateau mountain areas are distributed in the upper reaches of the basin.These areas are mainly cultivated land development and human activity gathering areas.The areas of constant landscape biodiversity in the basin are mainly glaciers/snow in the upstream and bare land and desert areas are on both sides of the downstream river.