Abstract. There are four components of carbon (C) pools in a natural forest ecosystem: vegetation, soil, litter and woody debris. Quantifying these C pools and their contributions to forest ecosystems is important in understanding C cycling in forests. Here, we investigated these four C pools in nine beech (Fagus L., Fagaceae) forests along an altitudinal gradient in southwest China. We found that the C pools of beech forest ecosystems ranged from 190.7 to 503.9 Mg C ha⁻¹, mainly attributed to vegetation C (accounting for 33.7–73.9 %) and soil C (accounting for 24.6–65.4 %). No more than 4 % of ecosystem C pools were stored in woody debris (0.25–3.4 %) and litter (0.2–0.7 %). Ecosystem C storage increased significantly with altitude, where the vegetation and woody debris C pools increased concomitantly with increasing altitude, while those of litter and soil exhibited no significant variations. The forest stand age was found to be a key driver of such altitudinal patterns, especially for vegetation C storage. The present study provides reliable data for understanding the structure and function of Chinese beech forests, and emphasizes the importance of considering the influence of stand age on C accumulation.