My 4 year old Golden Retriever has taken a liking to tree bark and wood chips. He goes so far as to pull the bark off the tree itself.
He eats Eukanuba Low Residue Adult dry dog food. I'm aware that this food is low in fiber, so I also give him cooked mixed vegetables with it every day for added fiber, as well as skin and coat powder (which is the only thing that has helped his hot spots).
Most dogs do this because they are bored and are looking for something to do. Be sure to provide him with plenty of activity toys so that he has enough to entertain him when he's outside.
The fear with the tree bark is that it will cause an intestinal obstruction (highly likely) so you want to nip this behavior in the bud as soon as you can.
If nothing else, you might have to remove the wood chips and put a liner around the tree to keep him from eating it.
Let me know if you still have questions.
Reply to Tammy Falkner's Post: This answer really deals with a dog who is bored in the back yard. That is not the case with my dog as we don't have a yard. His behavior occurs during daily walks and he seeks it out, as well as with paper products. Not sure this has to do with being bored during his 4 daily walks. Wanted to know if this meant some deficiency in his diet as well, such as fiber, etc.
It could be. Some dogs do this because they are anemic. If you have not seen the vet yet for basic bloodwork, I would go ahead and do that to rule this out and then go from there.
Not an active Expert