| Land is the basis of human survival and development.Scientific,rational and efficient utilization of land resources is crucial to the sustainable development of social economy.In the process of rapid development,the land use problems are becoming more and more prominent due to the combined effects of natural,social and economic factors,such as the reduction of land area,land degradation,non-agricultural land use,expansion of construction land area,ecological environment destruction and so on.The major change of land use structure and land quality not only affects the regional land use efficiency and the process of economic and social development,but also threatens the ecological environment security.Therefore,it is very important to study the characteristics,rules and influencing factors of the temporal and spatial changes of land use structure and landscape pattern for scientific and rational use of land resources,protection and improvement of ecological environment.Based on the land use data of four periods in 1990,2000,2010 and 2018,Guanzhong Plain District in central Shaanxi Province is taken as the research area.The land in Guanzhong Plain District is divided into nine land types,namely dry land,paddy field,woodland,grassland,water area,urban land,rural residential area,other construction land and unused land.At the same time,it can be divided into four functional types:land for food security(dry land and paddy field),land for ecological conservation(grassland,forest land,water area,unused land),and land for production and living(urban land,rural residential land,and other construction land).Land use dynamic attitude,land use composite index,land use transfer matrix and other methods were used to reveal the land use change status in Guanzhong Plain in recent 30 years.Combined with landscape ecology theory and method,landscape pattern index was used to quantitatively describe the change characteristics of landscape spatial pattern in Guanzhong Plain.The driving factors of land use change were discussed by combining qualitative and quantitative methods.The main research results are as follows:(1)Revealed the spatio-temporal variation characteristics of land use in Guanzhong Plain in recent 30 years.The main land use in Guanzhong plain area is dry land,accounting for 42.56%-45.34%of the total land area,followed by grassland,accounting for24.10%-24.61%of the total land area,and the lowest is other construction land,accounting for 0.12%-0.68%of the total land area.During the study period,the dryland area decreased gradually from 25202.77 km~2 in 1990 to 23653.86 km~2 in 2018.The area of forest land increased gradually from 1990 to 2000,and decreased from 2000 to 2018.The grassland area decreased from 13754.69 km~2 in 1990 to 13646.66 km~2 in 2000,and increased from342.42 km~2 in 2000 to 1140.05 km~2 in 2018,especially around Xi’an.(2)The land use degree and its conversion characteristics in Guanzhong Plain were analyzed.From 1990 to 2018,the single land use dynamic degree of production and living land showed an increasing trend,while the single land use dynamic degree of food security land showed a negative growth trend.The comprehensive land use dynamic degree was0.07%in 1990-2000,0.17%in 2000-2010 and 0.22%in 2010-2018.In the past 30 years,the degree of land use in the Guanzhong Plain has generally remained at a medium level and has gradually increased.During the study period,the ecological conservation land was transferred out of 1992.83 km~2 and transferred into 2053.19 km~2,and the food security land was transferred out of 2895.16 km~2 and transferred into 1253.16 km~2.Among them,the area of dry land transfer and transfer was the largest,which was 2769.28 km~2 and 1221.92 km~2,respectively.The production and living land was transferred out of 309.53km~2 and transferred into 1891.19km~2.Among them,rural settlements were mainly transformed into dry land and urban land,and dry land was transformed into rural settlements.(3)The spatial transfer characteristics of land use in Guanzhong Plain were analyzed.On the whole,the land use change in the study area from 1990 to 2010 and from 2010 to2018 was mainly the transformation of food security land to production and living land,which was manifested by the expansion of construction land and urban land area.From 2000to 2010,it was mainly the transformation of food security land to ecological conservation land,which may be due to the implementation of policies related to returning farmland to forest.From 1990 to 2018,the center of gravity migration of urban land showed a’Z’shape trend,among which the migration to the east from 2010 to 2018 was larger,with a migration distance of 6.94 km.From 1990 to 2018,the center of gravity migration trajectory of dryland generally shifted to the northeast,and the migration range was the largest from 2010 to 2018,with a migration distance of 0.38 km.The migration trajectory of the center of gravity of unused land showed a’V’shape feature.It moved to the southwest as a whole from 1990 to2010,and to the northeast from 2010 to 2018,with the largest migration distance of 14.77km.(4)The change characteristics of land use landscape pattern in Guanzhong Plain were monitored.During the study period,the dominance of land landscape was expressed as food security land>ecological conservation land>production and living land.The fragmentation of urban land and other construction land landscape types increased significantly,and the patch density increased from 0.002 to 0.010 and from 0.002 to 0.014,respectively.In the past 30 years,the number of landscape patches in the Guanzhong Plain has gradually increased,the patch density has not changed as a whole,and the fragmentation has not changed significantly.The Shannon evenness index increased from 0.59 in 1990 to 0.63 in2018,and the Shannon diversity index increased from 1.29 in 1990 to 1.38 in 2018.(5)The driving factors of spatio-temporal change of land use were discussed.Favorable terrain and climatic conditions are the natural factors of the spatial distribution pattern of land use in Guanzhong Plain,while non-agricultural population,grain yield and primary industry value are the human factors of the spatial and temporal changes of land use and landscape pattern in Guanzhong Plain in the past 30 years. |
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