Analysis On Temporal And Spatial Variation And Influencing Factors Of Natural Grassland Fractional Vegetation Cover In Northern Xinjiang

Natural grassland is an important renewable resource.The research on natural grassland is of great significance for ecological protection and economic development in arid and semi-arid areas.Based on MODIS-NDVI data from 1998 to 2018,combined with meteorological data such as precipitation,temperature,sunshine hours and relative humidity and Xinjiang statistical yearbook data,this study discusses the temporal and spatial changes and influencing factors of natural grassland vegetation coverage in Northern Xinjiang by using pixel dichotomy model,change rate analysis,coefficient of variation analysis and correlation analysis.Overall,the following can be concluded:(1)From 1998 to 2018,the average vegetation coverage of natural grassland in Northern Xinjiang in June,July,August,September and the whole year has great spatial differences,which is characterized by higher vegetation coverage in the West than in the East,higher vegetation coverage in the north and South than in the middle,and higher vegetation coverage in the mountains than in the desert.On the whole,it shows a spatial distribution trend of lower vegetation coverage in the middle and East,and higher vegetation coverage in the north,West and south.From 1998 to 2018,the annual average natural grassland vegetation coverage in Northern Xinjiang was 51.64%,and the monthly average natural grassland vegetation coverage was Jun e > July >September > August.The annual average natural grassland vegetation coverage in the five periods is not much different,but the average natural grassland vegetation coverage from 2015 to 2018 is slightly higher than that in other periods and slightly lower than that in other periods from 2010 to 2015.(2)From 1998 to 2018,the increasing trend of natural grassland vegetation in Northern Xinjiang(57.57%)was greater than the decreasing trend(42.43%).However,from June,August and September 1998 to 2018,the areas with increasing trend of natural grassland vegetation in Northern Xinjiang were smaller than those with decreasing trend,only the areas with increasing trend in July were larger than those with decreasing trend,and the improvement of grassland vegetation in growing season was July > June > August > September.(3)The fluctuation of natural grassland vegetation coverage in Northern Xinjiang generally shows that the north slope of Tianshan Mountains and Yili River Valley fluctuate great ly,while the fluctuation in other regions of Northern Xinjiang is small.The fluctuation degree of June,July,August,September and the whole year from 1998 to 2018 is mainly low fluctuation,relatively low fluctuation and medium fluctuation.(4)From June,July and August 1998 to 2015,precipitation and relative humidity significantly promoted the growth of natural grassland vegetation in Northern Xinjiang,and the temperature and sunshine hours in September significantly promoted the growth of natural g rassland vegetation in Northern Xinjiang;From 1998 to 2015,precipitation,relative humidity and temperature promoted the growth of natural grassland vegetation in Northern Xinjiang,but in comparison,the promotion of precipitation and relative humidity on the vegetation coverage of natural grassland in Northern Xinjiang was more clear.From 1998 to 2015,the vegetation coverage of natural grassland in Northern Xinjiang showed a negative correlation with the total population and animal husbandry.On the whole,the vegetation coverage of natural grassland decreased with the increase of the total population and fluctuated decreases with the continuous development of animal husbandry.