The colors and autumn foliage right outside of North Bay were astounding. Unfortunately, there was a lot of road construction in the area and we could not stop the car. This was a pity and to some extent haunted me for the rest of the trip. Next time…

I did have a chance to stop at the Serpent Riverfor to take some photographs. It was a lovely stop with a bunch of maple trees and a path that led under the bridge over the river to the north side where the river sped rapidly by a gorgeous red maple I could not miss photographing. I also photographed a number of individual leaves with my close-up lens.

The process of changing colors is fascinating. A green leaf is green because it contains a pigment known as chlorophyll. During the growing season chlorophyll is abundant in the cells of the leaf and as a result of that the green colors of the leaf dominate even though there are other colors present in the leaf. The green masks the other colors and as a result leaves of trees in summer are usually green.

Chlorophyll is very important in plants. It captures rays of the sun and uses the resulting energy to produce food for the plant. The plant eats the light and then uses the energy to manufacture the food that it needs from water and carbon dioxide. The sugars that are produced are the basis for the plant’s nourishment which is the sole source of the carbohydrates that the plant needs for growth and development.

The food manufacturing process of plants  “use up’ the Chlorophyll. In other words it is broken down in the process. During the growing season the plant replenishes chlorophyll and as a result the leaves stay green for the summer.

In the autumn when the daylight hours are reduced and temperatures cool and rays of the sun are lower  and  the chlorophyll degrades the pigments that were hidden by the green, such as  yellow and orange pigments are revealed. These pigments are found in the carotenoids that are present in leaves the whole year round, but their orange-yellow colors are usually masked by green chlorophyll.  In the fall the chlorophyll is replaced at a slower rate than it is used up and the supply of chlorophyll is gradually dwindling as a result and the masking effect fades away uncovering the glorious colors of autumn that slowly start to show through. As a result we see yellow, orange, brown and many hues between. These pigments are actually present during the summer it is just that we can’t see them.  I love how these colours are slowly revealed. I particularly love the transitional changes from green to orange or yellow.

The red pigments on the other hand are different. These are synthesized again once about half of the chlorophyll has been degraded. The reds, the purples, and their blended combinations that decorate autumn foliage especially in eastern North America come from another group of pigments in the cells called anthocyaninsthat are not present in the leaf throughout the growing season, but are actively produced only towards the end of summer. The process here is gradual as well showing the brilliant reds and purples.

In most temperate regions anthocyanins are present in only about 10% of the trees, but in some areas like New England they can be found in up to 70% of the trees. These colors appear vividly in the autumn eastern forests particularly trees such as maples, oaks, dogwoods, cherry trees and persimmons. These pigments can combine with the carotenoids’ colors to create the sensational orange, fiery reds, and burning bronzes typical of many hardwood species.

Together these processes produce the magic of autumn. They lead me to produce impressionistic images of autumn leaves, like the one below.

For quite a while I have suspected that climate change is altering the timing of the change of colors in autumn. Recent studies have shown that this might be true. Experiments have shown that poplar trees have stayed greener longer with higher levels of CO₂ even if temperatures remain the same.