Spatially explicit reconstruction of cropland cover in Europe from AD 1800 to 2000

One of the challenges in global change research is the significant uncertainty in global historical land use and land cover(LUCC)datasets,which are widely used as foundational data.In addition to the regional cropland area reconstructions,improving the grid allocation method is another feasible way to raise the reliability of historical LUCC data.In this study,an integrated reconstruction of the national cropland areas over the past 200 years was developed for 36 European countries.After that,the allocation algorithm was built using physiogeographic variables and historical city sites for accounting for land suitability and cultivation preferences,respectively.Finally,cropland data in Europe with a spatial resolution of 5′×5′at five time sections from AD 1800 to 2000 were generated using the optimal allocation algorithm in accordance with the stages of the regional history.The results were as follows:(1)The dominant factors governing the distribution of croplands in Europe vary at different agricultural stages,but the results can be merged together.Land suitability was more optimal for allocation during the modern agricultural stage(AD 1950 and 2000);the priority index combined with land suitability and cultivation preference was more reasonable for allocation during the traditional agricultural stage(AD 1800).The average of the allocations by priority index and the land suitability could be adopted as the allocation results during the transitional stage(AD 1850 and 1900)because the grids for absolute differences within±10 and±20 percentage points between the results obtained from the above two allocations were above 80% and 95%,respectively,which means the two allocation results could be merged.(2)Over the past 200 years,the total cropland area in Europe first increased to a peak in AD 1900 and then decreased.Spatially,the centre of the higher cropland fraction shifted from the western part of Europe in AD 1800 to the eastern part of the continent after AD 1950.(3)Both the cropland area and the spatial distribution in this study are more reasonable than the global dataset HYDE3.2.

Quantitative estimation and spatial reconstruction of urban and rural construction land in Jiangsu Province, 1820-1985

Land cover is the most evident landscape signal to characterize the influence of human activities on terrestrial ecosystems. Since the industrial revolution, the expansion of construction land has profoundly changed the status of land use coverage and changes. This study is proposed to reconstruct the spatial pattern of construction land （urban construction land and rural settlement land） for five historical periods over the past 200 years in Jiangsu Province with 200 m × 200 m grids on the basis of quantitative estimation. Urban construction land is estimated based on data about city walls, four gates along walls, and other socio-economic factors. Rural settlement land is calculated based on the rural population and per capita housing allowance. The spatial pattern of historical construction land is simulated based on the distribution of modern construction land in 1985 with a quantitative-boundary- suitability control method and thorough consideration over connectivity of different land use types. The study concludes that： （1） the amount of construction land in Jiangsu Province is estimated at 963.46 km^2 in 1820, 1043.46 km^2 in 1911, 1672.40 km^2 in 1936, 1980.34 km^2 in 1952 and 10,687.20 km^2 in 1985; and （2） the spatial distribution of construction land features the great proclivity to water bodies and main roads and the strong polarization of existent residence. The results are verified directly and indirectly by applying the trend verification of construction land changes and patterns, the correlation analysis between rural settlement land and local arable land, and quantitative accuracy test of the reconstructed construction land to actual historical survey maps covering four sample regions in 1936.