Analysis Of Vegetation Dynamics And Its Impact Factors In The Golmud River Basin

Vegetation is an important part of the global ecology,environment and energy systems.As an extremely important role on the the global ecological change process,it can effectively prevent desertification,slow down the concentration of greenhouse gases,and maintain global climate stability.Located in the south-central part of Qaidam Basin in Qinghai Province,the Golmud River Basin is arid and its ecology is fragile.Therefore,in order to protect the ecological environment of the Golmud River Basin,it is of great practical significance to explore the dynamic changes of vegetation in the Golmud River Basin.Based on the MODIS data from 2000 to 2017 as well as the Landsat data from 1994 to 2018,The spatiotemporal changes of vegetation cover and land use were analyzed in the Golmud River Basin in combination with various statistical analysis methods,and the main impact factors of vegetation growth were discussed in this region.The main results are as follows:(1)The vegetation grows well from June to September,and NDVI and EVI are higher at this time.The vegetation index showed a volatility growth during the 18 years.The spatial distribution of the vegetation index has obvious zonal characteristics.It is characterized by high in the south central region and low in other regions,respectively.(2)There is no supersaturation in NDVI in the area.Compared with EVI,it can better reflect the spatial variability of vegetation coverage in the study area,and has strong ability to identify vegetation differences.(3)The vegetation has improved generally since 2000,and the improvement area is larger than the degraded area.Compared to other seasons,the vegetation has the best growth in summer season.The linear regression method and the Sen+Mann-kendall method have good consistency for the results of vegetation change trend research.(4)The average value of Hurst index in the area is 0.589,and the vegetation is generally in a state of continuous improvement.In the future,the southern desert and the northern saline-alkali land will remain stable.The northern artificial salt pond area,the Wanli salt bridge as well as the human settlement area will continue to degrade,while the Golmud city,the natural vegetation as well as the region along the river will continue to improve.(5)The degree of vegetation coverage in the area is generally low,but it is increased.The average annual vegetation coverage rate is 23.3%.Low-medium vegetation,medium vegetation and high vegetation show an increasing rate,whereas both areas of bare soil and low-densityvegetation show a decreasing trend in the vegetation coverage.(6)The areas of unused land in the area are stable.The areas of cultivated land,woodland and construction land are increased while both areas of water body and grassland are reduced.The land use types are constantly interchanging,but the impact of human activities continues to strengthen.(7)NDVI has a strong correlation with precipitation,temperature,evaporation and relative humidity.(8)The relationship between vegetation and depth of groundwater table is relatively close.When the depth of groundwater table is about 1.5 m and 6.5 m,the natural vegetation and artificial crops grow well,respectively.(9)To some extent,human activities such as land reclamation,afforestation and urban expansion in Golmud have improved the ecological environment of the region and play a positive role on the ecological protection in the basin.