Hi roseunhip,
I wonder about a woodchuck? I used to have them mark trees like that. I wouldn't do a thing for the wound, except to keep it free of grass or weeds, so it can get air. I think the worst things for those wounds are moisture and not enough air to dry out. Good luck with it. I get very attached to trees too!

A woodchuck, now >thereI will try and put up one of those little wire fencing around the trunk to deter any repeat attack.
Thanks for the troubleshooting and advice, CatherineT!!

You're welcome roseunhip!
I have chicken wire around alot of my trees, to deter just about everything! I've actually seen woodchuck climb trees! But I think that the mark you're seeing is what they do to mark their territory.......although that is just a guess on my part. We used to have alot of woodchucks, and they never bothered my garden (with it's 3' chickenwire fence), but I've heard from others, that woodchucks can wipe out a garden overnight. Good luck with your tree healing. They are pretty good at doing that.

I have watched a woodchuck scale a 6' rabbit wire fence - I didn't know whether to laugh or cry. We've never had problems with bark eating, but they're munching on the echinacea now.

I couldn't believe my eyes, when I saw one climb a tree!
We used to have a family of them living under our wood shed. There used to be tons of them around our property, but I haven't seen one here in about 5 years. I think they never bothered my garden because we have a big piece of property, and there was probably always something closer for them to eat.