| Ordos City belongs to arid and semi-arid climate and is a typical agricultural and animal husbandry staggered area.In recent years,with the impact of global climate change and human activities,the vegetation ecosystem in Ordos City has undergone drastic changes,and the ecological vulnerability has become increasingly prominent.Systematic study of vegetation change and its driving factors,scientific evaluation of ecological vulnerability,can provide theoretical basis for ecological management and control in the region.Based on MOD13Q1 in the Moderate-Resolution Imaging Spectroradiometer(MODIS)dataset and the same period,this paper adopts the trend analysis method,stability analysis method,and continuous analysis method are adopted,partial correlation analysis,path analysis and residual analysis.The interannual and seasonal temporal and spatial changes of vegetation NDVI in Ordos City from2000 to 2020,the response of vegetation NDVI to climate change,and the impact of human activities on vegetation NDVI were analyzed.The ecological vulnerability in 2005,2010 and2018 was evaluated,and the factors affecting ecological vulnerability were analyzed through a geographic detector.The main results achieved are as follows:(1)The vegetation NDVI in Ordos City shows the characteristics of gradually decreasing from east to west in space.The vegetation growth trend is obvious in the past 21 years.Most of the improved areas appear in the eastern part of Ordos City;in the three seasons of spring,summer and autumn,the growth trend in autumn(0.0067/a)is greater than the growth trend in summer(0.0063/a)and the growth trend in spring(0.0041/a).Vegetation NDVI unstable areas appeared in the central part of Hangjin Banner and part of Wushen Banner.It can be seen from the continuous analysis If effective measures are not taken in the future,the vegetation will be degraded in a large area.(2)The growth of vegetation NDVI in Ordos is jointly affected by precipitation and temperature,of which precipitation is the main factor,and about 2.27% of the area is affected by the combined effect of precipitation and temperature;precipitation usually plays a positive role in the growth of vegetation NDVI,and temperature It mainly inhibits vegetation NDVI by affecting precipitation.Autumn precipitation had the strongest correlation with vegetation NDVI,and spring temperature had the strongest correlation with vegetation NDVI.The promotion of precipitation on vegetation NDVI was the strongest in summer,followed by spring and the weakest in autumn.The inhibitory effect of temperature on vegetation was the weakest in autumn,followed by spring and the strongest in summer.(3)The spatial distribution of vegetation NDVI in Ordos is closely related to the land use pattern,and the stable land use can be improved by the use of vegetation.The change of vegetation NDVI in Ordos is closely related to human activities and climate change.Human activities play a major role in the change of vegetation NDVI,and the contribution rate of human activities reaches 82.67%,The contribution rate of climate change is only 17.33%.(4)In 2005,2010 and 2018,the average value of the ecological vulnerability index in Ordos showed a downward trend,and the ecological vulnerability gradually improved.The three-phase data all show that the ecological vulnerability gradually increases from the east to the west in space.The amount of ecological transfer in the positive direction from 2005 to2010 is 38,108 km2,which is greater than the transfer amount from 2010 to 2018 of 25,038km2.The influence degree of each evaluation factor is different in different years of ecological vulnerability,but the average annual precipitation among natural factors,vegetation NDVI,and population density,livestock density,per capita GDP,and water consumption per 10000 yuan GDP caused by human activities are the main factors that affect Ordos City.The main factor of ecological vulnerability. |
