Hi Keith,

This damage is really interesting. Moose, porcupines, hare, voles, and squirrels all will feed on tree bark during the winter, but I typically see it more on willow and aspen. Given how high up the trunk it is and that it is a conifer, porcupine would be my thought on what may have caused this. According to ADFG, the inner bark of spruce, hemlock, and birch is a major food source for porcupines through the winter, and porcupine is most likely to have been able to reach these heights on the trunk and cause this much feeding damage. 

According to ADFG there are porcupines all throughout the state except some parts of the Alaska Peninsula and some islands. I also have seen observations of porcupines posted from the Liberty Falls area near Chitina, so I would think they are in Chitina as well. 

Here is some information about porcupines from ADFG: https://www.adfg.alaska.gov/index.cfm?adfg=viewing.landmammals&species=porcupine

Here is also an ADFG article where they talk about some research done on winter feeding by porcupines, which found white spruce and birch bark were important food sources for porcupines: http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=491

Hi Keith,

For the tree it looks like most of the damage occurred on one side, rather than all the way around the trunk, so the tree should seal that area off, and the other side where the bark hasn't been chewed should still be able to transport nutrients for the tree. Unfortunately this exposed area potentially could be an access point for tree diseases in the future, but the tree has its own way of compartmentalizing damage and hopefully should seal this off nicely. There are no tree products that can do a better job than the tree's natural process, so it's best to let the tree handle the damage. 

Porcupines can be tricky to keep away as they are such good climbers. Some people wrap the base of the tree with wire or flat sheets of aluminum, as shown here: https://wildlifehelp.org/solution/new-hampshire/porcupine/how-protect-my-trees-and-shrubs-porcupines/114#:~:text=Fencing%20trees%20and%20gardens%20is,enclosed%20in%20a%20single%20fence.

Here is a page that compares porcupine and squirrel damage. If you can get some binoculars to get a closer look you might be able to see marks from the teeth which might better be able to tell you what caused it. Porcupines have wider incisors than squirrels so their damage can be quite a bit more extensive: https://forestrynews.blogs.govdelivery.com/2018/05/04/porcupine-and-squirrel-damage-on-trees/

Hi Keith,

Yes it is ok to prune back those lower branches, the recommendation is typically to wait until late winter to do so when the tree is dormant. 

Here is a link to an AK DOF Community Forestry leaflet that shows how to cut large limbs. Link