In article . com,
a_plutonium wrote:
I had some awful rabbit attacks on a locust sapling and a 5 year old
apple tree whose trunk was about the
thickness of my upper arm. The rabbits ate all the way around and
about a band width of my hand. I had thought
both were going to die. But the locust started putting green circular
spots where the rabbits had eaten and the
tree is coming back in full force. The apple tree was hit worse by the
rabbits and appears as though the leaves
are coming in full force also.

Get some tree protectors before next winter.

So what is the deal with cambium and what does it take to kill a tree
by its cambium?

It's not unusual for severely damaged trees like this to start to leaf
in the spring, using resources already present in the branches, but if
the trees are as severely girdled as you describe, the new growth will
soon shrivel and die.

You may be able to save the trees by bridge grafting if you act fast
enough. The trees will probably try to come back from below the damage,
but if this tissue is below the graft you won't get the apples you
expect. For the locust, you can let it put up root sprouts, and clip
off most of them, letting the others develop into trunks.

Good luck!