Spatial-temporal Variation Characteristic And Distribution Simulation Of Cultivated Land In Wuhan Metropolitan Area

Farm land is an indispensable basic resource for the survival of mankind on earth.However,after entering the 21st century,the population is increasing and the farm land is gradually decreasing.Whether it is from the recent economic and industrial development of China's industrial and agricultural economy,or from the goal of guaranteeing the long-term strategy of national economic security look,we all need a reasonable use of limited arable land resources.The CPC Central Committee and the State Council have always attached great importance to the work of farm land protection,and have formulated a series of major policies and policies and identified"cherishing and rationally utilizing the land and effectively protecting the cultivated land" as one of China's basic national policy.In this paper,Landsat TM/ETM remote sensing images of 1995,2000,2005,2010 and 2015 were used as the main data,and the spatial-temporal distribution and driving forces of the dynamic change of cultivated land in Wuhan Megalopolis was analyzed.Furthermore,one land use collaborative optimization model,which called GWRCA-SDF was proposed to simulate the future's reasonable spatial distribution scheme for county scale region,some results and conclusion can be summarized as below:(1)During the period from 1995 to 2015,the total amount of farm land in Wuhan megalopolis maintain a tendency of decrease,and the total amount of cultivated land decreased by 230707.08 hm2 in 20 years.The largest number of reduction appeared in the 2005-2010 period and the number is 104626 hm2,with a change strength up to 3.55%;The reduction of paddy fields in Wuhan megalopolis was more than 2 times of that of dry land;The total amount of land that can be reclaimed and reclaimed in Wuhan Mmegalopolis is 83000.98 hectares,accounting for 42.40%of the Hubei Province.(2)The 9 cities with sharpest change of farm land in Wuhan Megalopolis are concentrated in the period of 2005-2010 and 2010-2015.In 2005-2010 periods,Huanggang City,Huangshi City,Qianjiang City,Wuhan City,Xiantao City,Xianning City and Xiaogan City has the largest change in the four time periods.Correspondingly,Ezhou City and Tianmen City in 2010-2015 holds the most obvious change in the four time periods,which indicating that the arable land protection of Wuhan Megalopolis is still quite backwards.(3)The entropy index(H)of land use structure in Wuhan Megalopolis is increasing slowly from 1995 to 2015.Hushi and Ezhou are the only two cities with their H index is higher than the average level of the entire megalopolis,while H index in the other cities are under the average value.From 1995 to 2015,main urban land of Wuhan City and Huangshi City holds the biggest annual average change rate of farm land and the trend was gradually decreasing from the middle of the urban area to the edge.The average annual rate of change of cultivated land on the eastern margin of the urban area is the slowest,and Yingcheng City in the western part is relatively slow.The degree of cultivated land change in the urban agglomeration of Wuhan shows a decreasing tendency from the margins of central and western part to their surroundings.(4)In the aspect of landscape structure and change,CONTAG decreased from 42.7073 to 38.6284 and AI decreased from 69.744 to 67.2128 in 1995-2015,indicating that the urban heterogeneity of the landscape increased with time;IJI increased from 61.7446 to 64.0422,which indicated that urban landscape is affected by the natural impact of weakening trend.The increasing of SHDI and SHEI further confirmed that the proportion of the dominant landscape type was decreasing and the spatial heterogeneity and fragmentation become higher gradually;The value of NP and PD were increased by 10.16%and 10.31%in 20 years,indicating the fragmentation degree of farm land in Wuhan Megalopolis increase;while LPI decreased from 35.0966 to 32.2399,indicating that farm land landscape was weakened by the largest farm land patch;ED increases with a rate of 5.64%,indicating that the complexity and instability of farmland path tends to increase;AI dropped from 75.6252 to 72.1154,with a reduction rate of 4.64%,indicating that the landscape layout of the farm land is more concentrated than the overall landscape layout,but the degree of aggregation is declining.(5)In the socio-economically backward counties,the number of farm land simulated by Traditional-CA will be more than that of the GWRCA-SDF model.These counties generally located at the edge of the city circle,the economy is relatively backward,and the city's radiation is small,there is less chance for the farm land converted into construction land.Compared with Traditional-CA model,the GWRCA-SDF will generate more farmland transfer out,but the flow to construction land accounted for a very small ratio;On the other hand,core urban area of Wuhan City as the largest urban built area in the city circle,where the transfer of farm land is less in the GWRCA-SDF model,which is of great significance to ensure food security,furthermore,most occupied farmlands were converted to built-up in these areas,which indicates that GWRCA-SDF has a higher yield of farm land than traditional-CA,and can sacrifice less farm land to ensure the stable development of urban construction.