Forest age significantly influences carbon (C) cycling and storage in tropical, temperate, and boreal biomes. Net primary productivity (NPP) and net ecosystem productivity (NEP) vary with forest age, with intermediate-aged forests (30–120 years) generally more productive than older or younger forests. In the youngest forests (0–10 years), NEP is negative in both boreal and temperate biomes, indicating carbon loss to the atmosphere. NEP trends across age classes show strong correlations with NPP, except in the youngest temperate forests. Heterotrophic soil respiration (Rh) is highest in the youngest temperate forests and declines with age, suggesting that forest respiration peaks when forests are young, not old. Carbon pools, including soil C, increase with age in all biomes. Forest age and disturbance history are key factors in regulating C cycling and storage. Understanding these patterns is crucial for improving knowledge of the terrestrial C cycle. The study synthesizes data on C pools and fluxes across age classes in different biomes, highlighting the importance of age in determining C dynamics. The results show that disturbance history and forest age significantly affect C cycling and storage, with implications for global carbon management and climate change mitigation.Forest age significantly influences carbon (C) cycling and storage in tropical, temperate, and boreal biomes. Net primary productivity (NPP) and net ecosystem productivity (NEP) vary with forest age, with intermediate-aged forests (30–120 years) generally more productive than older or younger forests. In the youngest forests (0–10 years), NEP is negative in both boreal and temperate biomes, indicating carbon loss to the atmosphere. NEP trends across age classes show strong correlations with NPP, except in the youngest temperate forests. Heterotrophic soil respiration (Rh) is highest in the youngest temperate forests and declines with age, suggesting that forest respiration peaks when forests are young, not old. Carbon pools, including soil C, increase with age in all biomes. Forest age and disturbance history are key factors in regulating C cycling and storage. Understanding these patterns is crucial for improving knowledge of the terrestrial C cycle. The study synthesizes data on C pools and fluxes across age classes in different biomes, highlighting the importance of age in determining C dynamics. The results show that disturbance history and forest age significantly affect C cycling and storage, with implications for global carbon management and climate change mitigation.