Are there any definitions of the wild/enchanted forests by literary scholars?I'm looking at a broad range of stuff like the Snow Queen, Hansel and Gretel, to Where The Wild Things Are and The Hobbit.
I think the best example of this for reference is "The Lost Woods" trope page on TV Tropes. Although it is not scholarly, it has just about every example of a lost, enchanted, haunted, vast, or otherwise notable forest in fiction. Also on that site are the "Ghibli Hills," a similar but somewhat more friendly version of the same vast, mysterious forest.
As far as scholarly articles, I could not find any specifically referencing the "enchanted forest" as a literary device, although it is certainly prevelant. The PDF below has some information, as does the Scribd document, while the Wikipedia link covers much of the same ground as the TV Tropes page, but from a more factual standpoint. Many of the sources linked in the Wiki page are from paper books, not available online, so research in a local library might be helpful.
Obviously, The Forest is a classic and well-known trope in fiction, and I think you can find examples of it in practically any genre, but since you are focusing on children's literature here, you might be well served to try Google searches with combinations of "children's literature," "wild/enchanted/lost/magic forest," "woods," and "jungle." This Google search page can be used to find articles with the same parameters. The forest is not always a place for fright and danger; see the "Hundred-Acre Wood" in Winnie-the-Pooh, for example, or the forest home of the Totoros in My Neighbor Totoro. Some of Rudyard Kipling's books may be useful, and of course J.R.R. Tolkien's books have their share of forests (The Hobbit was geared towards children more than his other works).
Most literary scholars would agree that in literature, an enchanted forest does not have to be enchanted in itself, but can contain enchantments. Enchanted forests are representative of liminality, which is a metaphysical concept refrencing to a subjective state of mind. The subjective state can be conscious or subconscious, but it describes an interpersonal experience of being between two different existential worlds. The enchantment in or of the forest can have both negative and positive affects. The character may undergo a dangerous threat or a peaceful refuge. The telltale sign that a character is encountering an enchanted forest is that it would be a place of magic in a location beyond normal travel where paranormal happenstances occur and eccentric even esoteric people appear.