Its territory is defined by wherever it is at the moment.

Territorial Baloth

Landfall — Whenever a land you control enters, this creature gets +2/+2 until end of turn.

The List

It knows nothing of Eldrazi or Planeswalkers, just that there are new intruders in its territory.

Battle for Zendikar

Landfall — Whenever a land enters the battlefield under your control, Territorial Baloth gets +2/+2 until end of turn.

Duel Decks: Zendikar vs. Eldrazi

Zendikar

A landfall ability doesn't trigger if a permanent already on the battlefield becomes a land.

A landfall ability triggers whenever a land you control enters for any reason. It triggers whenever you play a land, as well as whenever a spell or ability puts a land onto the battlefield under your control.

Whenever a land you control enters, each landfall ability of the permanents you control will trigger. You can put them   on the stack in any order. The last ability you put on the stack will be the first one to resolve (As a result, you can have those abilities resolve in the order of your choosing.).