Leaf-Crowned Elder has:
Kinship — At the beginning of your upkeep, you may look at the top card of your library. If it shares a creature type with Leaf-Crowned Elder, you may reveal it. If you do, you may play that card without paying its mana cost.
Leaf-Crowned Elder is a Treefolk Shaman. Does it allow me to cast Rootgrapple, a Tribal Instant — Treefolk, from the top of my deck?
I wouldn't have this doubt if it said subtype instead of creature type (in this case I'd know I can).