While dabbling in the tree growth probabilities I noticed, that some "normal" terrains have a good chance to grow Wasteland trees, like the Forested Mountain 2 of Desert where the Liana Tree is the fifth best tree with a chance of 20.8%. On the other hand, on Forested Mountain 2 of the Wasteland, the Beech is already the second best tree with a 32.2% chance.
While there is no strict rule against this, I think that the Wasteland concept is too distinct for mixing it like that. If others do agree, that it should be more separated I'd suggest to raise the temperature preference for all wasteland trees and the temperature for all Wasteland terrains by the same, significant amount. That should prevent Wasteland trees to ever grow on "normal" terrain and vice versa, while the distribution of Wasteland trees on Wasteland shouldn't change.
Sounds good to me :)