A couple of things crossed my mind concerning the two expansions if used together.

If you land on a space with a dragon scale and a fireland token and you choose to, or must, draw a dragon card, would you still lose a life at the end of your turn?

Also, if you're telported to a space with a fireland token and don't encounter the space, do you still lose a life?

I've not got the Firelands expansion yet so this may not be te case, but if so, since abilities affecting the adventure deck can only apply to dragon cards after they have been placed on the board, does this mean that only dragon cards already on the board can be burnt?

"If a character ends his turn in a space with a fireland token , he must lose 1 life." - So yes, you would lose a life if you were teleported there.

Talismanisland answered to the first question. Of course drawing cards from a dragon scale doesn't change that your turns end on that space, so yes, you still lose 1 life.

I've not got the Firelands expansion yet so this may not be te case, but if so, since abilities affecting the adventure deck can only apply to dragon cards after they have been placed on the board, does this mean that only dragon cards already on the board can be burnt?

Yes. That rule implies that no card in a Dragon deck can be burnt, just like you cannot apply any abilities or effects to them. Dragon cards faceup on board can be burnt, or affected by any abilities or effects targeting Adventure cards.