You've gotten a good explanation and some good examples. I'll choose a symbol in several works which might also help you. The forest is traditionally a place of darkness or evil--bad things happen in the forest, as that is where Satan lives, symbolically. This is particularly true in works set in the Puritan time.
The Crucible- the girls are up to no good in the forest with Tituba. We discover they've been dancing and spell-casting without their parents' knowledge or approval. This forest behavior is the root and cause of the Salem Witch Trials.
"Young Goodman Brown" - this Nathaniel Hawthorne short story is full of forest imagery connected to Evil. Goodman Brown actually meets the Devil there, finds all kinds of people who he had such respect for cavorting in a kind of satanic ritual, and even sees his lovely, innocent new wife there.
The Scarlet Letter- the forest is once again a forbidden place. Here it's the place where Hester seeks out Arthur Dimmesdale in order to reveal the identity of Roger Chillingworth. They make their plans and they deal with an unholy (but understandable) fit from Pearl at the side of the brook. (As a side note, I've always presumed the forest was the original meeting place for the the two lovers, as well, since anywhere else would have been too risky and because the forest was the place of hidden sin.)
"The Devil and Tom Walker" - another short story in which the Devil's work was done in the forest. Both Tom and his wife lose something to him in the forest--he loses his soul, and she loses her life.
Quoting a literary handbook from Bedford, a motif is "a recurrent, unifying element in an artistic work, such as an image, symbol, character type, action, idea, object, or phrase." A motif contributes to theme, but should be distinguished from theme. Motif informs and casts a revealing light on theme, while theme concerns specifically what a work says or reveals about its subject.
One such motif recurs in much Southern Gothic literature: the grotesque and the unnatural. In works by William Faulkner and Flannery O'Connor, for instance, the grotesque and the unnatural reveal the state of existence in the South following the Civil War.
In "A Rose for Emily," Emily, from somewhat of an aristocratic background, refuses to change following the loss of her social and economic status. Faulkner makes this concrete by displaying Emily poisoning her love interest, keeping the body long after it ceases to be a body and becomes a skeleton, and sleeping with it for years.
In "Good Country People," O'Connor presents a woman who is, herself, grotesque, in her appearance, behavior, and ideas, and then presents a young man, a Bible salesman, who conspires to steal her artificial leg.
Much fiction by Faulkner and O'Connor and other Southern Gothic writers is marked by the grotesque and unnatural.
I will continue the good work that has been started. The motif of memory and its role in constructing the subjective experience is something that can be seen in many post modern works. For example, Salman Rushdie in "Midnight's Children" has Saleem operate in a context where he struggles to maintain his own subjective experience in the face of a political order that wishes to remove his perceptions of memory in place of the consensus view where everything in India is fine. Milan Kundera plays with this idea in "The Book of Laughter and Forgetting," where memory plays a vital role in many of the vignettes. The pain it inflicts on the individual and the discomfort it creates for the state is something where one can see the theme of memory developed in great detail. Finally, the main character in Toni Morrison's, "Beloved," has sought to forget about her past and the killing of her daughter, something that reappears to her later on, reconfiguring past, present, and future in one indistinguishable mass of pain and misunderstanding.