Autumn Leaves: Identifying Trees in the Fall

Today in class we talked about identifying climax forests by their composition of trees and other plant species. When the leaves change in the fall (i.e. exactly what is happening now), it offers an unique opportunity to identify trees based on the color of their leaves. This means that we could look at a mountain- or hill-side and be able to know a little bit about what type of forest it is.

First, the basics. As Carl E. Palm explains on SUNY Environmental Science and Forestry's website, leaves change colors as a result of chemical processes that take place in the tree as the seasons change from summer to winter. During the summer, chlorophyll (this is the chemical that is responsible for photosynthesis) gives leaves their green color.  Leaves have yellow and orange pigments along with the green of chlorophyll, but for most of the year these colors are masked by chlorophyll and green coloring. In fall, days get shorter and the temperature drops, so photosynthesis stops. The chlorophyll breaks down, the green color fates, and the other pigments become visible. Simultaneously, other chemical changes may occur, which form additional colors. Temperature, light, and water supply can affect the degree and duration of fall colors. Low temperatures can make reds more brilliant, but an early frost mutes these colors.


A website called Forestry Education lists which types of trees typically turn which colors:

Red: Red Oaks, Maples, Sweetgum, Dogwood
Yellow/Orange: Hickory, Ash, Maples, Yellow Poplar, White Oaks, Beech, Birch, Sycamore

ALSO,
Evergreen (don't change colors/loose leaves): Pines, Spruce, Firs, Hemlock, Cedars


Knowing what colors tree species turn can help identify trees (next weekend in the Adirondacks!), which can help us determine the age of a forest.