Abstract: Aims Ecological stoichiometry has been recognized as a useful indicator of nutrient status and process regulation in ecosystems. Quantifying the effects of stand age on carbon (C) : nitrogen (N) : phosphorus (P) stoichiometric characteristics and ecosystem C storage allocation patterns is critical for understanding the mechanisms of biogeochemical cycles and ecological functions in plantation ecosystems. Methods This study compared the C:N:P stoichiometry and the C storage partitioning patterns along a chronosequence of walnut (Juglans regia) plantations in the eastern Taihang Mountains, North China. Plant and soil samples from four stand ages (4-, 8-, 12-, and 16-year-old) were collected and analyzed. Important findings 1) Mean C content in organs (root, stem, branch, and leaf) was 437.17, 449.87, 448.16, and 441.39 g·kg-1, respectively, showing a nog-significant increasing trend with stand age. N and P contents of different organs were 4.15-26.68 g·kg-1 and 0.99-1.95 g·kg-1, respectively, decreasing significantly with stand age. C:N and C:P ratios increased significantly, while N:P remained stable. 2) Under anthropogenic management, soil C, N, and P contents exhibited an initial decline followed by an increase with stand age, with significant variations among age classes. Trends in C:N, C:P and N:P ratios aligned with nutrient content changes. 3) Correlation analysis showed that soil C was positively correlated with soil N (P < 0.001). Leaf C showed a negatively correlation with leaf N (P < 0.05), while leaf N demonstrated a significantly positive correlation with leaf P (P < 0.01). Soil P was positively liked to leaf N, branch P, stem P and N (P < 0.01). 4) Total ecosystem C storage for 4-, 8-, 12-, and 16-year-old plantations was 167.59, 123.69, 136.03, and 202.37 Mg·ha-1, respectively. The soil layer constituted the primary C pool, contributing 88.2%-99.7% of total ecosystem C storage. This study provides a scientific basis for systematically understanding nutrient cycling mechanisms and C sequestration functions in mountain economic plantation ecosystems.

Key words: C:N:P stoichiometry, carbon storage, stand age, Juglans regia, Taihang Mountain