is a work of art that is divided into three sections or panels; the term was originally applied to paintings and sculptures, and then later to sets of three (usually-related) photographs. Technically speaking, this isn't really a triptych, as it's a single photograph. Still, the three distinct elements -- the dead leaves trapped between the two contrasting tree trunks -- immediately brought the term to mind. Even better, each of the three is a different kind of tree: a maple log below, beech leaves, and of course, the distinctive white of birch at the top.
Incidentally, I actually stumbled upon this scene while waiting for the sky to darken so I could take some moonlight shots. Always look around, you never know what is underfoot. :)