I need to reread the English translation, but it should be once per turn, only one time within your eight actions, then you can do it again after waking up for the next turn.
In an earlier version (around the time the tokens were designed), one of the Forest's actions turned a random location into flamewood forest, so there were some extra copies of that tile. Also, the game was originally intended to be played with a map drawn as you go. The tiles were an adition, unlocked during the campaign, that a friend offered to add to the game. I will definitely look at the file again and balance the amount of each tile. Thank you for the heads up.