I have a few suggestions for you. First, you can try using a spray bottle filled with water and spraying the cat whenever it tries to climb the tree. This is a non-harmful way to discourage the cat from climbing the tree. Additionally, you can try placing double-sided tape around the base of the tree. The sticky texture of the tape will deter the cat from trying to climb the tree. Finally, you can try providing the cat with its own special climbing area or toys to distract it from the tree.