In addition to being a stump, a log from the original tree can also have a nostalgic feeling attached to it. It is interesting how something natural can evoke someone's feelings, or have a history behind it (Usually feelings are attached to something more materialistic). For example, this stump has been located at my house since I moved there over ten years ago!
It will be very interesting to see how the peers in our class using trees in their projects will modify them. A tree is a symbol of life, knowledge, etc and these meanings seem to be very universal. Any modification to them will enhance the artist's purpose behind it.