| Cultivated land resource is the foundation that human society relies on to exist and develop.Africa is rich in land resources,but relatively short of arable land resources,which directly affects Africa's food supply and food security.As a kind of spatial continuous complex,cultivated land resources in Africa are constantly changing in area,quantity,state and function over time,which has an important impact on driving regional and even global ecological environment changes.Therefore,scientific exploration of cultivated land resource endowment in Africa,accurate identification of cultivated land pattern characteristics,and comprehensive disclosure of the law and process of dynamic change of cultivated land are of great guiding significance for food security and ecosystem change process analysis in Africa and even the world.At present,there are many sets of remote sensing data for land use that can be used for remote sensing monitoring and analysis of cultivated land resources.However,generally speaking,these data have low spatial resolution,poor regional suitability,and are difficult to form long time series data sets,so it is impossible to accurately describe the dynamic change trend analysis of spatial pattern of cultivated land resources in the region.GlobeLand30,as the world's first set of land cover data with 30m spatial resolution,includes the two benchmark years 2000 and 2010,which provides data guarantee for the analysis of spatial distribution and dynamic changes of cultivated land on a global or continental scale.Therefore,this paper uses GlobeLand30 cultivated land data product to study the spatiotemporal changes of cultivated land use pattern in Africa based on multi-scale and multi-index in Africa research region.The main research contents and results of this paper are as follows:(1)Quality assessment of GlobeLand30 data in Africa.In this study,the quality assessment of GlobeLand30 data in Africa was conducted using a two-level sampling test model of spatial data.The overall accuracy of the products in Africa in 2000 was 93.68%.In 2010,the overall accuracy of the product was 93.43%.The product quality of the data in the two periods was relatively stable,maintaining more than 93%.Among all land use types,cultivated land showed high precision in producer's and user's precision.In 2000,the average overall precision of cultivated land products was84.23%,and in 2010,the average overall precision was 83.17%.The application of GlobeLand30 data in Africa was feasible.(2)Analysis of spatiotemporal changes of cultivated land use in Africa.Based on the spatial distribution information of cultivated land in Africa,the temporal and spatial characteristics of cultivated land in Africa from 2000 to 2010 were analyzed from five scales,including Geographic region,country,latitude and longitude network,climate zoning and ecological zoning.From the area characteristics,the cultivated land area increased by 2.26×10~5 km~2,an increase of 11.20%over2000-2010.Cultivated land was mainly distributed in east and west Africa,and Nigeria had the largest cultivated area.The size of African countries varied by-27.57%-25.17%between 2000 and 2010.The largest increase was in Nigeria(25.17%)and the largest decline was in Cote d'lvoire(-27.57%).In ten years,the distribution of cultivated land in latitude was stable,and fluctuated from west east increase.The most widely distributed cultivated land areas in the climatic belt was desert climate(17.42%).The largest cultivated land area in the ecological zone was successively tropical shrub forest belt,and the tropical desert belt showed the most significant increase in cultivated land rate,which was 15.77%.(3)Analysis of transition changes of cultivated land use in Africa.From the transition characteristics,the newly increased cultivated land was mainly transferred from the development and utilization of forest land,grassland and shrub land and other vegetation types,and the reduced arable land was mainly transferred into forest land,grassland and shrub land.The newly increased arable land area was much larger than the reduced area.(4)Analysis of intensive changes of cultivated land use in Africa.From the intensive characteristics,in 10 years,the multiple cropping index of cultivated land in Africa increased by 11.70%and the change rate was 13.54%.From the perspective of five geographical regions,the multiple cropping index in west and central Africa as a whole was higher than that in other regions.In 2000,west Africa(149.93%)had the largest i the multiple cropping index in Africa,followed by central Africa(132.37%)and South Africa(132.37%).The ranking trend of the multiple cropping index in various African regions in 2010 was similar to that in 2000.In 10 years,the increase and change rate of the multiple cropping index in East Africa(25.41%)were the largest,while the change rate in north Africa was the smallest(5.46%).From the perspective of reclamation index,the reclamation index of central African countries was generally high.The change of reclamation index in ten years showed an increasing trend on the whole,among which the growth rate in central Africa was the highest,reaching25.25%.The main features and innovations of this paper were as follows:(1)Based on the two-level sampling inspection model of spatial data and high spatial resolution data,the technical method of quality assessment of cultivated land data GlobeLand 30 in Africa was established and implemented in micro level,and integrated validation analysis was carried out in macro level,which provided a new idea and method for precision evaluation of cultivated land data products in large overseas areas,and provided an important support for the analysis and application of GlobeLand30.(2)Using the data products of GlobeLand 30 in 2000 and 2010,and introducing 10 indicators,such as area quantity,spatial location,type conversion and intensive utilization,three indicators groups for the analysis of spatial and temporal patterns of cultivated land in Africa were established.Systematic analysis was carried out at national,ecological and climatic scales,revealing the current situation of cultivated land utilization in Africa and the characteristics and laws of spatial and temporal changes in the past 10 years.Through the calculation of Hunger Index and reclamation index,the impact of temporal and spatial changes of cultivated land on food security in Africa was analyzed,which would play a guiding role in the rational development and utilization of cultivated land resources in Africa in the future. |
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