The Reconstruction Of Historical Cropland And Forest And Its Carbon Emission In China During Past 300 Years

By modifying the bio-geophysics and bio-geochemistry of the earth surface,Land Use and Land Cover Change(LUCC)led by human activities significantly effects on the energy input-output equilibrium and material circulation,further regional and global climate and ecological environments.Moreover,such effects have been reinforced along with the population growth and technology advances.According to statistics,during 300 years since the Industrial Revolution,about 42%-68%of the global land surface has been influenced by human land use activities,at the mean time,carbon emission has reached 177 Pg,i.e.,about 30%of the global human initiated carbon emission.In addition to the burning of fossil fuels and cement production to produce large amounts of carbon emissions,land use/cover change induced by human activities has become an important factor to lead the change of the terrestrial carbon reserves.This influence by human activities have further exceeded beyond the rate and extent of carbon emission resulted from the natural variability.So,it will helps for reducing the uncertainty in estimated carbon reserves of land ecosystems to accurately assess the changes of the ecosystem's carbon balance caused by the LUCC which caused by human activities.Historical LUCC is an essential component of global changes and key parameters to establish a model for global environmental changes,such as carbon circulation,climate and ecological change.The existence of the lag effect in the climate and ecological changes renders reconstructing a high-resolution historical land use dataset of high significance to analyzing and predicting carbon circulation,climate and ecological effects caused by historical land use changes.Since the 1990s,quantitative reconstruction of historical land use,especially global and regional farmland and grassland in the past 300 years,has made a great progress as pushed along together by research plan such as LUCC,BIOME300,GCTE,GLP,iLEAPS,PAGES and Future Earth.This study aim at reconstructing the spatial pattern of historical cropland and forestland,then estimating its carbon emission in China over the past 300 years.Based on summarizing the reconstruction of historical land and the estimation of carbon emission in domestic and foreign,we have collected and compiled data on China's historical population,cropland and forestland over the past 300 years.Then,coupling the different process and mechanism of the change of cropland and forestland respectively,we have build a partition synchronization Cellar Automate model aim at reconstructing the historical farmland spatial pattern and a historical forestland reconstruction model based on the preference selection behavior of the agents.So,we have reconstructed the spatial pattern of historical cropland and forestland in China over the past 300 years representing by the grid with a resolution of 1km×1km.Further,the response curve of ecosystem disturbance in the different scenarios and ecosystems have been established.Based on the Bookkeeping model,the amount of ecosystem carbon emission induced by the disturbance of cropland and forestland have been calculated in the different scenarios.The main conclusions are listed as follows:(1)The model embodies a multi-region synchronization modeling ideology.In simulating a large-scale spatial pattern with various evolution paths and rules,it emphasizes the spatial variations in both evolution paths and evolution speed caused by spatial heterogeneity by setting multiple synchronous evolution regions,selecting factors influencing on the cropland spatial pattern,assigning weights to all influencing factors,and training coefficients for each region to establish a whole set of coefficients.The construction of historical cropland concentrated in traditional agricultural region;cropland reclamation gradually moved to Northeast China,Yun-Gui Plateau in Southwest China,and Gan-Ning region in Northwest China;and cropland reclamation rate increased within the traditional agricultural reclamation area.(2)From the opinion of the agent's preference,coupling the amount of historical forestland with the spatial pattern of reconstructing historical cropland and potential forestland region,a historical forestland reconstruction model based on the preference selection behavior of the agents have been established.The reconstructed historical forestland in China over the past 300 years concentrates in DaXingAnLing,XiaoXingAnLing,ChangBaiShan,HengDuanShan,DaBaShan,WuYiShan,DaBieShan,XueFengShang and etc.In terms of the evolution of the spatial pattern,historical forestland shrinks gradually in LiaoHe plains,SongHuaJiang-NenJiang plains,and SanJiang plains of the northeast of China,Sichuan basins and YunNan-GuiZhou Plateaus.(3)Considering the effect of carbon emission resulting from land reclamation and forest harvest,we have built the local parameters value of ecosystem disturbance in the different scenarios,and estimated the change of carbon reservation induced by the change of cropland and forestland in China's vegetation and soil carbon over the past 300 years.Our result shows that the amount of carbon emission resulting from LUCC in China over the past 300 years is ranged from 9.25 Pg?26.83 Pg,the optimal estimate is 15.64 Pg.However,the amount of carbon emission induced by the land reclamation and forest harvest is ranged from 2.66 Pg?5.63 Pg,6.49Pg?21.20 Pg respectively,and the optimal estimate is 3.16 Pg and 12.47 Pg respectively.(4)Our estimation is much less than the main stream results of carbon emission in all over the world,which makes a strong foundation for figuring out the responsibility of carbon emission reduction and dealing with the international negotiation.