Analysis Of Ecological Environment Change In Horqin Sandy Land Using Multisource Data

For more than a century,the global ecological environment has undergone dramatic changes,such as vegetation degradation,water shortage,increasing desertification,and other issues,profoundly affecting the human environment.Horqin Sandy Land,one of China's four major sandy lands,is situated at the semi-arid temperate continental monsoon climate zone.In the ecotone of agriculture and animal husbandry,frequent natural environment changes and human activities render the ecological environment fragile and cause rapid desertification.A long-term dynamic monitoring of Horqin Sandy Land is performed to identify its water resource status and present sandy land and vegetation cover.This study provides preliminary data for land use structure adjustment and ecological environment improvement.In this study,the GRACE satellite gravity data,well data,Landsat MSS/TM/ETM+/OLI satellite imagery data,meteorological data,and socioeconomic data were the main data sources.The GRACE data processing method,the CPC hydrological model,the GLDAS hydrological model,the supervised classification method,the post-classification change detection method,and the center-of-gravity migration model were taken as the main research methods.This study focused on the ecological environment change process of Horqin Sandy Land from the 1980s to 2016,summarizing the research achievements of domestic and foreign researchers and the characteristics of Horqin Sandy Land.We established a highly operational and wide application of the ecological environment analysis and evaluation system for Horqin Sandy Land using the scientific method.The main contents and results of this study are as follows:(1)This paper clarified the natural geography and socio-economic characteristics of Horqin sandy land,which set the background for analyzing and evaluating the process of ecological environment change in this area.From the analysis of natural geography,we can find that the region has loose soil,less rainfall and uneven rainfall during the year and annual fluctuations in rainfall.The region's annual average temperature is rising,and windy weather is frequent.From the analysis of socio-economic characteristics,we can find that the region's population,cattle stocks,GDP and per capita net income of the farmers and herdsmen have increased.At different times,the state and local governments have formulated a series of policies to encourage reclamation and immigration.(2)In this paper,the water resources monitoring system of Horqin sandy land combined with GLDAS hydrological model,CPC hydrological model,monitoring point water well data and water supply information was established,the changes of land water reserves and groundwater reserves in Horqin sandy land were discussed,and the response of water reserves changes to the local meteorological conditions and agricultural patterns.Results show that the groundwater storage in the region is declining at a rate of-13.2± 2.6 mm/year.On the basis of the soil moisture calculated by GLDAS and terrestrial water storage change by GRACE,the change in groundwater storage was calculated and compared with the change in groundwater storage in the area calculated from the monitoring well data.The results of the two calculations are consistent,indicating that the groundwater storage in Horqin Sandy Land from 2005 to 2010 was continuously consumed,with an overall consumption rate of approximately-13.5 ± 1.9 mm/year.Finally,a combination of the meteorological data and local agricultural model analysis indicates that arid climate and groundwater extraction are key factors influencing water consumption in Horqin Sandy Land.(3)This paper analyzed the dynamic change process of land use in Horqin sandy land under long time sequence,and found out the spatial pattern,spatial transfer characteristics,the track and the rate of gravity migration.From the analysis of land use status,the main land use types are vegetation,water body,construction land,sandy land and arable land.The vegetation is mainly distributed in the Horqin Left Back Banner,the northwest of the Kulun Banner and the middle east of the Naiman Banner.The main water body is the River Basin of Xiliao and small lakes scattered around the region.The construction land is mainly distributed in the urban area of banner,country and city,and and arable land and grassland coverage.The sandy land is mainly distributed in Horqin Left Middle Banner,Horqin Left Back Banner,and the north of Kulun and Naiman Banner.The cultivated land is mainly distributed on both sides of the Xiliao River Basin and the southern part of the Horqin Sandy Land.From the analysis of the land use change,the construction area and cultivated land area of Horqin Sandy Land increased steadily to 1219.7 km2 and 16,209.8 km2 in 2016,respectively,and the dynamic degrees in these areas were 0.61%and 1.04%,respectively.The water area continued to decrease to 682.7 km2 in 2016,with a dynamic degree of-1.21%.In addition,the vegetation and sandy land area had greater instability.Vegetation experienced a significant reduction,recovering to 15,198.7 km2 in 2016,with a dynamic degree of-0.33%;sandy land experienced two periods of growth in 1990 and 2010.Sandy land has gradually been controlled since 2010,with the area reduced to 6355.1 km2 by 2016 and a dynamic rating of-0.73%.The vegetation center of gravity migrated to the northwest at a rate of 64.6 m/a,and water bodies migrated to the southeast at a rate of 389.3 m/a.Construction land and cultivated land both migrated to the northeast at rates of 53.6 and 379.5 m/a,respectively.Sandy land migrated to the southwest at a rate of 379.5 m/a.(4)From the view of landscape type,the trends of the landscape of the construction and cultivated lands in Horqin Sandy Land are consistent,and both fragmentations are weakened.The complexity of the patch shape is enhanced,and the dominance is improved.The complexity of the patch shape and the dominance in the vegetation landscape and sandy land are reduced,the vegetation fragmentation degree is enhanced,and the landscape fragmentation degree of the sandy land is reduced.The fragmentation degree of the water body is reduced,the complexity of the patch shape is enhanced,and the dominance degree is reduced.From the view of landscape level,the landscape pattern of Horqin Sandy Land is simplistic,and its landscape type is unbalanced;the dominance of the cultivated land and vegetation landscape is increasing,and the advantage of the water landscape is decreasing.