I made one of these a while back, made a new class to handle the tree by its location, if the tree wasnt added to the arraylist, once you started chopping it it was automatically added. The tree's even disappear for 1 minute after being cut down ;D
I made a better one than this, if tree id is this, time down is this, else if tree id is this etc.
Handling the tree stump in action handler made more sense, blaintly because its an action.