An interesting fact about why / how the leaves fall.

  Deciduous plants were traditionally believed to shed their leaves in autumn primarily because the high costs involved in their maintenance would outweigh the benefits from photosynthesis during the winter period of low light availability and cold temperatures. In many cases this turned out to be over-simplistic - other factors involved include insect predation, water loss, and damage from high winds or snowfall.

  Anthocyanins, responsible for red-purple coloration, are actively produced in autumn, but not involved in leaf-drop. What use is the production of pigments in leaves that are about to fall? A number of hypotheses have been proposed, which fall into two cageories: interaction with animals, and protection from non-biological factors.

  According to the photoprotection theory, anthocyanins protects the leaf against the harmful effects of light at low temperatures. It is true that the leaves are about to fall and therefore it is not of extreme importance for the tree to protect them. Photo-oxidation and photo-inhibition, however, especially at low temperatures, make the process of reabsorbing nutrients less efficient. By shielding the leaf with anthocyanins, according to the photoprotection theory, the tree manages to reabsorb nutrients (especially nitrogen) more efficiently.

  Whatever the reason, tourists and locals alike appreciate the variety and spendor of experiencing Autumn in The Great Smoky Mountains National Park.