Tribal is not a permanent type. Lignify can only count as the enchantment for Muldrotha's ability.
110.4. There are five permanent types: artifact, creature, enchantment, land, and planeswalker. Instant and sorcery cards can't enter the battlefield and thus can't be permanents. Some tribal cards can enter the battlefield and some can't, depending on their other card types. See section 3, "Card Types."
Those aren't even card types; they are Supertypes. Muldrotha doesn't care about them.
110.4. There are five permanent types: artifact, creature, enchantment, land, and planeswalker. Instant and sorcery cards can't enter the battlefield and thus can't be permanents. Some tribal cards can enter the battlefield and some can't, depending on their other card types. See section 3, "Card Types."
Rule 205.1: The type line is printed directly below the illustration. It contains the card’s card type(s). It also contains the card’s subtype(s) and supertype(s), if applicable.
Rule 205.4a: A card can also have one or more supertypes. These are printed directly before its card types. The supertypes are basic, legendary, ongoing, snow, and world.
110.4. There are five permanent types: artifact, creature, enchantment, land, and planeswalker. Instant and sorcery cards can't enter the battlefield and thus can't be permanents. Some tribal cards can enter the battlefield and some can't, depending on their other card types. See section 3, "Card Types."
Rule 205.4a: A card can also have one or more supertypes. These are printed directly before its card types. The supertypes are basic, legendary, ongoing, snow, and world.
RULES OF MAGIC :
http://magic.wizards.com/en/game-info/gameplay/rules-and-formats/rules