  We show that strong coupling between graphene and the substrate is mitigated
when 0.8 monolayer of Na is adsorbed and consolidated on top
graphene-on-Ni(111). Specifically, the {\pi} state is partially restored near
the K-point and the energy gap between the {\pi} and {\pi}* states reduced to
1.3 eV after adsorption, as measured by angle-resolved photoemission
spectroscopy. We show that this change is not caused by intercalation of Na to
underneath graphene but it is caused by an electronic coupling between Na on
top and graphene. We show further that graphene can be decoupled to a much
higher extent when Na is intercalated to underneath graphene. After
intercalation, the energy gap between the {\pi} and {\pi}* states is reduced to
0 eV and these states are identical as in freestanding and n-doped graphene. We
conclude thus that two mechanisms of decoupling exist: a strong decoupling
through intercalation, which is the same as one found using noble metals, and a
weak decoupling caused by electronic interaction with the adsorbate on top.
