Our Mr. Tolkien, it seems, most definately had a fear associated with forests. In The Hobbit, there was Mirkwood, in our story, The Old Forest (so far)
Now, in the end, the forests turn out to be more queer than evil. Scary, but only because they are very mystical. Perhaps those who grow up in more open country (like rural England) become fearful when they cannot see the horizon.
People who move here to our heavily-forested part of NC comment on feeling claustrophic at first, not being able to see the horizon and having to crane their necks to see open sky.