Three cities located in Southern Fujian,namely Xiamen,Zhangzhou,and Quanzhou,were selected as the study area.The grey correlation model was employed to identify the driving effects of preliminary factors on the changes in cultivated soil organic carbon from 1982 to 2018.Based on the main driving factors identified,a BP neural network model was constructed to simulate and predict the trends in carbon sources/sinks from 2019 to 2055.The results indicate that:1)soil properties(sand content,clay content,initial soil organic carbon density,etc.),external environmental condi-tions(road accessibility,annual average temperature,annual precipitation,etc.),and agricultural management measures(straw returning amount,tillage intensity,organic or nitrogen fertilizer appli-cation amount,etc.)are the main driving factors of cultivated soil organic carbon changes over the past 30 years,with correlation coefficients of carbon source/sink to these factors all above 0.83.2)The carbon model established based on the main drivers fits the carbon source/sink changes in the study area quite well,with a relative error of the simulation values of 1.11%and a simulation effi-ciency of 0.48,both meeting the verification.3)Over the next 30 years,the average soil organic car-bon density in the study area's cultivated land is projected to increase by 0.15 kg·m-2,generally exhib-iting a carbon sink behavior.However,soils in different regions have dual functions of carbon source and sink.The proportion of"carbon source"soils accounts for 30.33%,primarily located in plain and terrace areas or in cultivated lands with higher initial organic carbon densities."Carbon sink"soils,characterized by an increase in organic carbon density of≤1 kg·m-2,make up 97.10%of the total area of"carbon sink"soils.Therefore,priority should be given to the soils with carbon source effect,and specific emission reduction measures should be developed to transform"sources"into"sinks".Be-sides,it is also recommended to further improve the carbon sequestration and sink capacity of soils to prevent high-carbon soils from experiencing carbon loss,which could lead to a carbon source effect.
维普
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