Carbohydrate content governs growth-storage allocation during recovery from carbon depletion.

How plants prioritize carbon (C) allocation between growth and storage remains an outstanding question, limiting predictions of forest C cycling and ecosystem resilience following periods of C limitation. To address this gap, we experimentally depleted carbohydrate reserves via low-CO2 conditions and quantified C allocation to reserves and growth during recovery at ambient CO2 in Fagus sylvatica juveniles. Trees with lower carbohydrate reserves following C depletion prioritized C allocation to storage, whereas trees replete with carbohydrates favored growth, demonstrating that internal carbohydrate status governs allocation priorities during recovery from periods of C limitation. Our findings show that storage-growth allocation during recovery from C limitation is driven by internal carbohydrate status, identifying plant carbohydrate concentration as a key variable for parameterizing the substrate-dependent sink strength that current process-based vegetation models largely omit.