Studies On The Temporal And Spatial Dynamics Of The Ujumqin Sandy Land In The Past 35 Years

A total of 8 remote sensing images of the Ujimqin Desert from 1985 to 2020 were selected.Based on Arc GIS 10.3 and ENVI 5.3,and taking the Ujimqin Desert as the study area,the remote sensing images were used to analyze the area,vegetation coverage changes,land use dynamics,and desertification driving factors of the Ujimqin Desert from 1985 to 2020.The main research conclusions are as follows:1.Ujumqin sandy area as a whole shows a trend of desertification mitigation and reduction in the extent of desertification area.The sandy area shrinks from 2013.95 km~2in 1985 to 1873.29 km~2in 2020,and the total sandy area decreases by 140.66 km~2,with an overall reduction of 6.98%;the desertification range gradually shrinks from the east-west direction of Guanxi Uzhumqin Banner to the central part,and the sandy distribution shows more concentrated aggregation.2.From 1985 to 2000,vegetation coverage showed a decreasing trend,with a decrease of 303.25 km~2,mainly occurring in the eastern and western parts of the sandy land.After 2000,vegetation coverage increased overall,with an increase of 214.71 km~2,mainly occurring in most of the eastern and some central areas of the sandy land,accounting for 35.96%of the total increased area.3.The change in grassland area in the Ujimqin Desert shows a trend of first rising,then falling,and finally stabilizing.From 1985 to 1995,the natural grassland area was in a declining phase,accounting for 3.5%of the total study area.From 1998 to 2014,the grassland area increased continuously,with the maximum area in 2014 reaching 1742.11km~2,accounting for 4.1%.From 1985 to 2020,the water area in the study area overall decreased first and then increased,from 13.94 km~2in 1985 to 12.36 km~2in 1995,then increased year by year,reaching the maximum water area in 2020 at 20.02 km~2.From1985 to 1990,the construction area increased by 0.08 km~2,while from 1990 to 2005,it remained at a similar level.From 2005 to 2015,it continued to decrease by 0.12 km~2,and the total construction land area in 2020 increased by 0.85 km~2compared to that in 1985.4.The center of gravity of the Ujimqin Sandy Land is shifting towards the northeast as a whole,and the trend line shows fluctuations,indicating that the desertification of the Ujimqin Sandy Land is relatively stable and has slowed down to some extent.From 1985 to 2020,the centroid of the sandy land in the Ujimqin Desert moved a total distance of 50.44 km over nearly 35 years.In terms of the main axis direction,the long axis expanded from 1.88 km in 1985 to 32.33 km in 1995,then shrank to 2.61 km in 2005,and finally to 2.13 km in 2020,indicating that the change trend of the Ujimqin Desert during this period is an overall contraction in the"south-north"direction.From the secondary axis direction,the short axis changed from 1.51 km in 1985 to 1.69km in 2020,indicating that the change trend of the Ujimqin Desert in the past 35 years still presents a contraction in the"southeast-northwest"direction.