Despite its pivotal feedback to carbon cycling, representing the dynamic response of vegetation to nitrogen limitation is a key challenge for simulating the terrestrial carbon sink in land models. Here, we explore a representation of this dynamic response of vegetation to nitrogen limitation with a novel representation of biological nitrogen fixation and nitrogen cycling in the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) model. First, we assess how incorporating this dynamic response of vegetation to nitrogen limitation via biological nitrogen fixation influences carbon sequestration for CO₂ and nitrogen fertilisation experiments, comparing simulations against observation-based estimates from meta-analyses. This evaluates whether underlying mechanisms are realistically represented. Second, we assess how incorporating the dynamic response of vegetation to nitrogen limitation via biological nitrogen fixation affects carbon sequestration over the late 20^th and early 21^st century, examining the effects of global change drivers (CO₂, nitrogen deposition, climate, and land use change) acting both individually and concurrently. Including nitrogen cycling reduces the terrestrial carbon sink driven by elevated atmospheric CO₂ concentration over the historical period. Representing the dynamic response of vegetation to nitrogen limitation via biological nitrogen fixation increases the present-day terrestrial carbon sink by 0.2 Pg C yr^-1 because the upregulation of biological nitrogen fixation driven by stronger nitrogen limitation under elevated atmospheric CO₂ concentration alleviates nitrogen limitation. Our results highlight the importance of the dynamic response of vegetation to nitrogen limitation for realistically projecting the future terrestrial carbon sink under global change with land models.