Contrasting molecular‐level carbon traits underlying leaf and root economic strategies in a subtropical forest

Abstract Carbon constitutes the biochemical basis of plant survival and evolution. Plant trait‐based economic frameworks have revealed divergent strategic trade‐offs in leaves (leaf economics spectrum, LES) and roots (root economics space, RES). However, how carbon molecular compounds coordinate with organ‐specific economic strategies and whether they follow similar biochemical foundations remain unknown. We employed the solid‐state 13 C nuclear magnetic resonance to quantify key carbon functional groups in leaves and roots across 13 coexisting subtropical tree species and assess their coordination with LES and RES. The results showed contrasting coordination of carbon traits with economic strategies in leaves and roots. Specifically, leaves with the acquisitive strategy prioritized physiologically active and nitrogen‐rich carbon over structural carbohydrates used for longevity maintenance, while defence carbon compounds decoupled from the LES. However, roots exhibited a primary trade‐off where bioactive carbon aligned against defence compounds along the conservation gradient. Orthogonally, root structural carbohydrate proportions traded off against carbon molecular diversity, aligning to the root collaboration gradient from ‘do‐it‐yourself’ soil exploration to collaboration with mycorrhizal fungi. Synthesis. These findings highlight divergent carbon bases in shaping above‐ and below‐ground multidimensional economics trait space, providing new mechanistic insights into whole‐plant strategic trade‐offs that govern plant adaptations and species coexistence in heterogeneous environments.