Final answer:
Bridge grafting is used to repair a damaged bark at the base of a tree, by using healthy scions to bridge the gap and allow healing.
Step-by-step explanation:
The type of grafting used to repair a damaged bark at the base of a tree is bridge grafting. This method involves taking healthy scions (branches or buds) from the same tree or a closely related species and grafting them over the damaged area. The scions bridge the gap in the bark, allowing the tree to heal by growing new bark over the wounds from the top down and from the ends of the scion inwards, reconnecting the circulatory system of the tree.