Assessing the regional carbon sink with its forming processes- a case study of Liaoning province, China

Assessing the regional carbon sink sets the basis of regional carbon management, which involves many measures but has large uncertainties. Carbon sink assessment scheme based on its forming processes (CSF) is a recently proposed measure but repeatly calculates emission from water erosion and ignored human inducing carbon inputs. Therefore, we revised the CSF by calculating the direct outputs from land surface and adding human returned carbon (HC) to the input. The revised CSF thus involved gross primary productivity (GPP), ecosystem respiration (ER), carbon removal from cropland (CRC), emission from reactive carbon (E_RC), emission from water erosion (E_wat), and HC, which can be obtained from public data sources. Then the revised CSF was applied to the Liaoning province of China. The estimated carbon input of Liaoning province during 2000-2014 was 114.77 ± 8.41 TgC yr^-1, while the carbon output was 110.48 ± 8.38 TgC yr^-1. The difference between input and output induced a carbon sink of 4.30 ± 2.20 TgC yr^-1, accounting for 3.75% of total carbon input. The carbon sink spatially decreased from northeast to southwest, which was highly correlated with that of GPP. However, though its forming fluxes significantly increased from 2000 to 2014, the carbon sink showed a decreasing trend. In addition, the revised scheme only needed published and public data, which made it serve as an alternative approach for regional carbon budget assessment.