Climate Change and Rising CO2 Amplify the Impact of Land Use/Cover Change on Carbon Budget Differentially Across China

Given the increasing attention to climate change and rising CO2 (CCRC) in the global carbon cycle, we remain unclear about how China's unprecedented land use/cover change (LUCC) in the carbon budget has been affected by CCRC in recent decades. Here, we combined remotely sensed land use/cover (LUC) datasets and the Biome-BGCMuSo model to address this issue by setting different scenarios. We found that LUCC led the carbon sink to increase by approximately 104.24 +/- 46.52 Tg C without considering CCRC during 1990-2020. Carbon sinks contributed by afforestation (374.97 +/- 36.50 Tg C) and grassland planting (15.75 +/- 9.11 Tg C) offset other LUC trajectories caused carbon loss (286.47 +/- 32.18 Tg C, 87.33% owing to agricultural reclamation). LUCC contributed carbon sinks were amplified by similar to 20% under CCRC at the national scale. This rate increased to 106.03% in northeast China but decreased to -26.68% in southern China. CCRC led carbon sink contributed by afforestation amplified by 85.11% in northeastern China but was only 26.35% in southern China. CCRC amplified carbon emissions due to agricultural reclamation by 103.20% in northeastern China and by 25.09% in southern China. Our results demonstrated that ecological restoration projects are efficient in enhancing carbon sinks and mitigating emissions. Divergent amplifying/reducing effect of CCRC across different geographic regions implied the sensitivity of different LUC trajectories to CCRC varied with different climate backgrounds. Land management strategies should be implemented with spatial heterogeneity to amplify afforestation and grassland planting contributed carbon sinks and decrease other LUC trajectories caused carbon loss under the global change environment.It is undoubted that climate change and rising CO2 (CCRC) would alter the effect of land use/cover change (LUCC) on the carbon budget. However, to what extent CCRC will influence the effect of LUCC on the carbon budget remains unclear. In this work, we evaluated the impact of CCRC on the carbon budget change caused by LUCC. We found that CCRC would amplify or dampen the impact of LUCC on the carbon budget. Meanwhile, this amplifying or dampening rate was divergent in different geographic regions. Our work provides new insights for making climate change mitigation targeted land decisions to increase carbon sinks with ecological restoration and construction and reduce emissions through protection.