Cats are naturally drawn to the scent of Christmas trees, so it's common for them to want to climb them. To prevent this, you can try placing a few double-sided sticky pads on the lower branches to deter your cat from climbing the tree. You can also try spraying the tree with a citrus-based solution or cat-repellent spray to discourage your cat from approaching it. You can also try placing the tree in a secure location that your cat can't reach, such as a high shelf or a room that your cat isn't allowed in.