Does humility stop my Dryad Arbor from being able to tap for mana?

Question

Does Humility remove the mana ability of land creatures such as Dryad Arbor?

Answer 1

Yes. A land creature is a creature, mana abilities are abilities, and Humility removes all abilities from all creatures.

A creature is a creature, no matter what other types it may have:

300.2. Some objects have more than one card type (for example, an artifact creature). Such objects combine the aspects of each of those card types, and are subject to spells and abilities that affect either or all of those card types.

Mana abilities are abilities:

605.1. Some activated abilities and some triggered abilities are mana abilities [..]

The inherent mana ability of lands with a basic land type, such as Dryad Arbor, can be treated as if it was printed on the card:

305.6. [..] An object with the land card type and a basic land type has the intrinsic ability “{T}: Add [mana symbol],” even if the text box doesn’t actually contain that text or the object has no text box. [..]

In the layer system that determines an object's characteristics, its base characterstics (the copiable values) are set in layer 1, animation effects happen in layer 4, and finally Humility removes all abilities from creatures in layer 6:

613.1a Layer 1: Rules and effects that modify copiable values are applied.

613.1d Layer 4: Type-changing effects are applied. These include effects that change an object’s card type, subtype, and/or supertype.

613.1f Layer 6: Ability-adding effects, keyword counters, ability-removing effects, and effects that say an object can’t have an ability are applied.

Therefore, Humility removes the mana-generating ability from land creatures, whether they are inherently creatures such as Dryad Arbor or they have been animated otherwise.