r In the summer I wrote about the amazing aspen forests and their family root system. In the fall we see the colors of the aspen groves as eye candy that we rush out to photograph each year. Now, as we move into the winter months, there is another unique feature of the aspen trees to amaze us: chlorophyll in the bark.
When we think of chlorophyll, we normally think of tree leaves. The aspen tree is unusual in that the tree bark has a high concentration of chlorophyll that is capable of carrying out photosynthesis and the production of carbohydrates normally reserved for leaves. This is a remarkable adaptation to the environment in which the aspen trees live. They must not only survive but thrive in a climate of relatively cool summers and cold winters at an altitude of altitude of 5,000 to 12,000 feet. The creator has enabled the aspen to produce food even in the winter months.
Aspen bark is very thin and the chlorophyll layer lies within about 1/32 inch of the exterior surface of the bark. The exterior surface is called the periderm, and when you brush the tree bark with your hand, the white that comes off on your hand is the dead periderm cells. The photosynthetic layer comprises only about 5 percent of the total volume of the bark of an aspen tree but accounts for 30 to 50 percent of the carbohydrate production as the leaves. This indicates the importance of the bark to the nutrition of the tree and how unusual it is from other trees that lose their leaves and become dormant during winter. This also gives the aspen tree a head start in spring growth.
This carbohydrate resource does not go unnoticed during the hard winters and becomes a food source for forest wildlife. Deer and elk strip the bark from aspen trees when grass is not available. Burrowing animals such as gophers dig and feed upon the roots. The amazing aspen tree is a miracle for the whole forest.