Autumnal leaves in vibrant colors are a lovely aspect of the season, but they are vital for keeping trees alive. Have you ever wondered the reason why trees changing colors is so fascinating? As summer ends and the chiller days start to rise, the green leaves change their colors to turn to autumn.

We’ve collected a few reasons to answer your question; let us look at them listed below:

Table of Contents

1. Preparing for Winter

Trees in winter
Trees in winter | Image Credit – Flickr

Most leaves are green in color during the summertime as these leaves receive a good amount of energy absorbed from the sunlight to generate chlorophyll for photosynthesis. The summertime is ideal for the trees as chlorophyll is constantly replaced.

As the season changes, the leaves adjust accordingly; as the temperature drops and the days get shorter, the leaves also receive less sunlight to produce chlorophyll. The nitrogen molecule used in trees is used resued and broken down, hence why changing colors occur.

Since the timing of leaf color change is more dependent on light than on temperature, leaves change color at around the same time each year. Carbohydrates are moved from the leaf to the branch when deciduous trees reach this light threshold, and no additional minerals are brought in. With their leaves, the trees are ready to split. 

2. The chlorophyll breaks down

The chlorophyll breaks down in fall
The chlorophyll breaks down in fall | Image Credit – Freepik

A combination of day length and night temperature is the catalyst for developing fall color.

As the days shortens, the amount of sugar produced by photosynthesis decreases, and hormones in the plant cause the leaf to close and shed. Cold nights hasten this process, but the lower temperatures also affect the compounds that stay in the leaf, causing them to break down more quickly.

Chlorophyll’s green tint is so intense that it obscures any other pigment. The lack of green allows the different hues to shine in the fall. Carotenoids are pigments found in leaves; xanthophylls are yellow (like corn), and carotenes are orange (like carrots). Anthocyanins (found in blueberries and cherries) are pigments created only in the fall when bright and chilly weather.

Because the trees have cut off most contact with their leaves at this time, the trapped sugar in the veins of the leaves encourages the synthesis of anthocyanins, which are reddish pigments required for plant defense. However, trees come in various colors in the fall, including brown, golden bronze, golden yellow, purple-red, light tan, crimson, and orange-red.

The amount of chlorophyll and other pigment proportions define the color of a leaf. Brown leaves are made up of anthocyanin and chlorophyll, while orange leaves contain anthocyanins and carotenoids. Low temperatures that are still above freezing aid in producing anthocyanin, a brilliant red pigment.

However, an early frost reduces the color by preventing the formation of anthocyanins. Drought can also drive leaves to fall off and turn brown. Color displays are intense but brief where only a few tree species predominate, such as in New England and Northeast Asia.

The longer the exhibition, the more diverse the forest. Colors become bland when cloudy and warm weather, like in Europe. A layer of cells grows where the leaf’s stem joins the tree, eventually cutting the tissue that holds the leaf to the tree.

The limb where the leaf was attached has a closed scar; the leaf is now free to fall when encouraged by wind, gravity, rain, and other factors. The leaves turn a drab brown when they die, and the chloroplasts are entirely broken down. That is the science behind the various colors of autumn leaves, ranging from red to yellow to orange to bronze to brown.

3. Changes take place in trees

Other changes occur as the fall colors emerge—a specific layer of cells forming on the leaf stem progressively severe the tissues supporting the leaf. Simultaneously, the tree seals the incision, leaving a leaf scar when the leaf is eventually blown off or falls from its weight.

In the fall, most broad-leaved trees in the north lose their leaves. The dead brown leaves of oaks and a few other species, on the other hand, may remain on the tree until growth resumes in the spring. Some broad-leaved trees in the South, where winters are mild, are evergreen, meaning their leaves remain on the trees throughout the winter and retain their green hue.

4. Weather affects color intensity

Red maple leaves changing color and fall off trees due to change weather in autumn season
Red maple leaves changing color and fall off trees due to change weather in autumn season | Image Credit – Freepik

The degree and duration of fall color are influenced by temperature, light, and water supply.

Anthocyanin production is favored at low temperatures above freezing, resulting in brilliant red maples. On the other hand, early frost will dull the vivid red color. The intensity of fall colors tends to increase on rainy and gloomy days. On a clear, dry, and chilly (but not freezing) day, the most incredible time to see the autumn colors would be.

5. Climate change effects on leaf colors:

Climate change effects on leaf colors | Video Credit – NBC News Learn

Daylength and temperature are the two key environmental parameters that trees determine fall color. The onset of leaf senescence is triggered by the shortening of days in August and September. The length of the day signifies the end of chlorophyll production and the beginning of chlorophyll degradation that the trees use. They use daylength as their primary cue since it is a dependable indicator of the impending arrival of winter as daylength decreases.

Depending on where the earth is in its orbit around the sun, with regularity, Temperatures, on the other hand, can vary greatly. Variations in the weather have a significant impact. Plants consider temperature when deciding how to grow.

How quickly chlorophyll degrades and how much color pigment is created or expressed. If the fall weather is cool or colder than usual, trees’ chlorophyll breakdown and leaf color changes are accelerated. The appearance of fall colors will delay or relatively subdue if the weather is warmer than usual.

All indications point to long-term warming temperatures as a result of climate change. Climate change is wreaking mayhem on the world’s temperature and the predictability of weather patterns. Seasonal hints color will become entirely out of sync if the day length and temperature relationships get entirely out of sync.

The course of events will be completely unpredictable. Some trees’ peak color will appear considerably later in the season. Others may transition from green to brown without the intermediate color, as they have in the past production period.

The impact of climate change on tree distributions is an even bigger mystery. The sugar maple is a good example. This tree thrives in cooler climates and is the main tree in New England forests, but it may become extinct in the United States as temperatures rise. The tree is expected to move. Few trees remain in the United States, decimating maple syrup production in New York.

Vermont, New Hampshire, New York, and Maine will be hit hard by the recession in England.

The loss of the fall foliage will have the same effect on the leaf-peeping tourist economy, but maybe the worst part is that it will deprive us, our children, and their children’s children of the unfettered delight that comes with being alive. It would be a pity if you missed out on viewing the lovely colors of the woodland in the fall.

Wrapping Up

It is fascinating and unique how leaves change color during the fall season. It showcases the beauty of mother nature and how significant impact sunlight and even the slightest temperature can make to turn the leaves from green to yellow and brown. 

(Last Updated on April 24, 2022 by Sadrish Dabadi)

Thinley Doma Ghale holds a Bachelor’s degree in Social Work from Kathmandu University. She enjoys writing articles on climate change animals and loves to travel and experience new ideas, places, meeting people, and learning from them. As a social science student, research has always been her area of interest.