Unevenly distributed CO₂ and its impacts on terrestrial carbon uptake under the changing land uses

Changes in land-use structure and pattern can affect both atmospheric CO₂ concentrations and the terrestrial carbon budget. To explore the effects of non-uniformly distributed CO₂ concentration on terrestrial carbon uptake under land-use changes, this study integrated global CO₂ concentrations, Net Primary Productivity (NPP), and land-use data under historical period and SSP1-2.6, SSP2-4.5 and SSP5-8.5 scenarios from 1850 to 2100. Land-use intensity (LUI) and the CO₂ correlation to NPP were calculated using partial correlation analysis by controlling LUI. The results showed that NPP growth over the forest was the highest among the land-use types, reaching 0.54 g C·m², 2.06 g C·m² and 4.64 g C·m², respectively, under SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios. Among all the scenarios, the average correlation levels of atmospheric CO₂ and NPP considering the LUI effect and controlling LUI ranged respectively from 0.34 to 0.68 and from 0.32 to 0.61 at a 5 % level of significance. It suggested that sensible land use planning might enhance the CO₂ fertilization effect and that rises in CO₂ concentrations could stimulate terrestrial carbon absorption. The findings add to the body of knowledge about the effects of atmospheric CO₂ on terrestrial carbon uptake and serve as a scientific guide for protecting terrestrial carbon stocks and managing land use.