China’s naturally regenerated forests currently have greater aboveground carbon accumulation rates than newly planted forests

China has restored extensive forest areas through afforestation and natural regeneration, contributing to climate change mitigation. However, the restoration patterns and the mechanisms driving aboveground carbon accumulation in these forests remain unclear. We mapped the distribution of the aboveground carbon accumulation rates for China’s young planted and natural forests in 2020 and identified key factors influencing their variability using remote sensing and field data. The analysis reveals marked spatial heterogeneity in aboveground carbon accumulation rates of these restored young forests, driven primarily by seasonal temperature. At comparable ages, young planted forests show lower aboveground carbon accumulation rates than young natural forests, mainly due to different tree density. Although young planted forests currently sequester more carbon, projections indicate that by 2060 its total aboveground carbon stock will be lower than that of young natural forests. Consequently, our findings emphasize optimizing forest structure in managing China’s planted forests to enhance carbon storage. China’s afforested forests have higher tree densities and slower aboveground carbon accumulation rates than naturally regenerated forests, but they currently store more carbon because of their larger covered areas, according to an analysis of national forest inventory and remote sensing data.