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Accurate projections of the terrestrial carbon (C) sink are critical to understanding the future global C cycle and setting CO₂ emission reduction goals. Current earth system models (ESMs) and dynamic global vegetation models (DGVMs) with coupled carbon‐nitrogen cycles project that future terrestrial C sequestration will be limited by nitrogen (N) availability, but the magnitude of N limitation remains a critical uncertainty. Plants use multiple symbiotic nutrient acquisition strategies to mitigate N limitation, but current DGVMs omit these mechanisms. Fully coupling N‐acquiring plant‐microbe symbioses to soil organic matter (SOM) cycling within a DGVM for the first time, we show that increases in N acquisition via SOM decomposition and atmospheric N₂ fixation could support long‐term enhancement of terrestrial C sequestration at global scales under elevated CO₂. The model reproduced elevated CO₂ responses …