I think if you move the tree higher or out of the dogs way then your dog isn't really learning that if you say he must not touch something then he must not touch it.
It depends on the age of the dog/pup - a young puppy may well be able to understand quite quickly that you don't want them to touch; but learning the self-control
not to touch something they know that they shouldn't takes a lot longer, and really - is it worth the extra hassle at Christmas?
It gets incredibly stressful and tedious to keep saying "no, no, no" all the time, while trying to enjoy a family Christmas - teaching a dog/puppy anything at holiday time is hard enough as they are bound to be excited and stressed by the change in routine, let alone add to their temptations by leaving a decorated tree within reach.
I'm sure that a floor=standing Christmas tree isn't that important, is it?