No, only when once building them.
Also, use your imagination. You can either use groves for "forests", ala DE, that cannot be built on, and then allow straggler [i.e. individual] trees to be built on/removed.
Or..... you can put a max number of destructible trees for each building [probably determine it by obstruction size of each building], so that if you hover a Barracks over, say, 3 trees it allows you to place the foundation, while if there are 4 or more trees it denies you. That way you can't just plop it right down in the middle of a forest.