My kitties have never really taken a real interest in the tree - at least climbing wise. All we have on the bottom are unbreakable ornaments and candy canes, and other than the occasional ornament found somewhere in the kitchen or mud-room (about three rooms away from the living room, where we have the tree), we have no big problems with having a christmas tree.
Though Echo does find it nice to have her own personal bush inside the house, we (as good pets for the kitties) have kept all the presents pushed toward the outside so Echo can have her personal cave underneath the pretty tree.
Perfect place to ambush Clover!

Oh that is so priceless! I'm sure Autumn didn't MEAN to knock it over! She probably thought it would be a great picture opportunity to have her as an ornament! And it would have, if the tree was only strong enough to hold her squirming kitty-weight.