Fall continues in Eberwhite Woods - Leaves and Mushrooms Oh My!
Why Do Leaves Change Color?
Almost every parent, grandparent, and teacher has been asked "Why do leaves change color?" Kids are naturally curious about this phenomenon they can witness themselves - a great time to take a walk in EWW with your child and have a conversation about pigments, changing leaf colors, and work on your tree ID. Here is a fantastic article from (http://eekwi.org/veg/trees/treestruecolor.htm) that summarizes "Why do leaves change color?" nicely.
Leaf color comes from pigments. Pigments are natural substances produced by leaf cells. The three pigments that color leaves are:
- chlorophyll (green)
- carotenoid (yellow, orange, and brown)
- anthocyanin (red)
Chlorophyll is the most important of the three. Without the chlorophyll in leaves, trees wouldn't be able to use sunlight to produce food.
Carotenoids create bright yellows and oranges in familiar fruits and vegetables. Corn, carrots, and bananas are just a few of the many plants colored by carotenoid.
Anthocyanins add the color red to plants, including cranberries, red apples, cherries, strawberries and others.
Chlorophyll and carotenoid are in leaf cells all the time during the growing season. But the chlorophyll covers the carotenoid -- that's why summer leaves are green, not yellow or orange. Most anthocyanins are produced only in autumn, and only under certain conditions. Not all trees can make anthocyanin.
As the Earth makes its 365-day journey around the sun, some parts of the planet will get fewer hours of sunlight at certain times of the year. In those regions, the days become shorter and the nights get longer. The temperature slowly drops. Autumn comes, and then winter.
Trees respond to the decreasing amount of sunlight by producing less and less chlorophyll. Eventually, a tree stops producing chlorophyll. When that happens, the carotenoid already in the leaves can finally show through. The leaves become a bright rainbow of glowing yellows, sparkling oranges and warm browns. What about red leaves? Read on.
Perhaps you've noticed that in some years, the red fall colors seem brighter and more spectacular than in other years. The temperature and cloud cover can make a big difference in a tree's red colors from year to year.
When a number of warm, sunny autumn days and cool but not freezing nights come one after the other, it's going to be a good year for reds. In the daytime, the leaves can produce lots of sugar, but the cool night temperatures prevent the sugar sap from flowing through the leaf veins and down into the branches and trunk. Anthocyanins to the rescue! Researchers have found out that anthocyanins are produced as a form of protection. They allow the plant to recover nutrients in the leaves before they fall off. This helps make sure that the tree will be ready for the next growing season. Anthocyanins give leaves their bright, brilliant shades of red, purple and crimson.
The yellow, gold and orange colors created by carotenoid remain fairly constant from year to year. That's because carotenoids are always present in leaves and the amount does not change in response to weather.
The amount of rain in a year also affects autumn leaf color. A severe drought can delay the arrival of fall colors by a few weeks. A warm, wet period during fall will lower the intensity, or brightness, of autumn colors. A severe frost will kill the leaves, turning them brown and causing them to drop early. The best autumn colors come when there's been:
- a warm, wet spring
- a summer that's not too hot or dry, and
- a fall with plenty of warm sunny days and cool nights.
You can use fall leaf color to help identify different tree species. Look for these leaf colors on the trees in your neighborhood:
- Oaks: red, brown or russet
- Hickories: golden bronze
- Maple trees show a whole range of colors:
- Sugar Maple: orange-red
- Black Maple: glowing yellow
- Red Maple: bright scarlet
A tree's roots, branches and twigs can endure freezing temperatures, but most leaves are not so tough. On a broadleaf tree -- say a maple or a birch -- the tender thin leaves, made up of cells filled with water sap, will freeze in winter. Any plant tissue unable to live through the winter must be sealed off and shed to ensure the tree's survival.
As sunlight decreases in autumn, the veins that carry sap into and out of a leaf gradually close. A layer of cells, called the separation layer, forms at the base of the leaf stem. When this layer is complete, the leaf is separated from the tissue that connected it to the branch, and it falls. Oak leaves are the exception. The separation layer never fully detaches the dead oak leaves, and they remain on the tree through winter.
Evergreen trees -- pines, spruces, cedars and firs -- don't lose their leaves, or needles, in winter. The needles are covered with a heavy wax coating and the fluids inside the cells contain substances that resist freezing. Evergreen leaves can live for several years before they fall and are replaced by new growth.
On the ground, fallen leaves are broken down by bacteria, fungi, earthworms and other organisms. The decomposed leaves restock the soil with nutrients, and become part of the spongy humus layer on the forest floor that absorbs and holds rainfall. In nature, nothing goes to waste!
Mushroom Species in Eberwhite Woods
Eberwhite Woods has exploded with mushrooms in the last couple of weeks, thanks to all of the rain and warm temperatures. Some mushrooms are big and showy, but the majority are very small and camouflaged with the colors of the forest. Mushrooms are fascinating organisms to examine closely over a few days as the fruiting bodies emerge, release spores, and then decompose. Mushrooms come in all shapes, sizes, and lifestyles, and reproduce asexually and sexually. It's complicated! Below, are very basic diagrams of a mushroom life cycle and anatomy, but many species do things differently.
Please go explore the world of mushrooms with your children in Eberwhite Woods! Kids love to look at mushrooms and are really good at finding tiny, interesting ones. While some mushrooms are edible, many more are not edible and are toxic, and this applies to the mushrooms of Eberwhite Woods. Use caution when searching for mushrooms with children or adults. Enjoy what the rain brings!
Mushrooms in EWW - Fall 2018 (all photographs taken in EWW)
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A new mushroom species discovered in Eberwhite Woods 53 years ago!
On Sept 25, 1965, Frances Hoseney, an assistant working with Dr. Smith at The University of Michigan discovered a new species of mushroom in Eberwhite Woods. As of now, it is unique to Eberwhite Woods - only one specimen has ever been found.
Patricia Rogers, the collection manager from The University of Michigan Herbarium wrote this summary for us:
Boletus eberwhitei is the scientific name of a species of mushroom. The term "species" describes any unique group of living or once-living things that generally look similar and act similarly. For example, monkeys are a big group of animals, in which the chimpanzee is a species of monkey. A species can be living today, or discovered only through fossils. It can be known, or unknown and waiting to be discovered.
A known species is identified by its scientific name, which is usually in Latin or Greek, and often underlined or printed in italics. Boletus eberwhitei is one species in a larger group, the fungus family Boletaceae, sometimes called the "boletes" or “sponge caps”. All the species in the boletes share the physical characteristic of developing their spores in very narrow tubes. These tubes give the underside of their caps a spongy appearance, which is an easy way to first recognize a bolete—but after that, you have to figure out which species it is!
How a newly discovered species is made known:
When scientists discover an organism they think is a new species, first they do an investigation to make sure it was not discovered and written about earlier. Then, they make the new species known by publishing a scientific description of it in a book or science journal.
A scientific description is written according to a set of rules that make sure all the important information about the new species is included. The description must also include the new species’ scientific name, which is created by the scientist.
A "type" specimen must also be listed in the description. This specimen is very important because it is the evidence that the new species actually exists. The type is placed in the appropriate museum collection so other scientists can also examine it and better understand the new species. A fungus specimen like Boletus eberwhitei would be placed in an herbarium.
More members of the new species may be collected, and frequently are, but they are compared against the type or the scientific description to confirm their identity—this process of identifying specimens is also known as "determination".
Alexander Smith was a mycologist—a scientist who studies fungi. He thought the mushroom Florence Hoseney collected in Eberwhite Woods looked different from any mushroom in the Boletaceae that he already knew. He searched through many books and journals to see if another mycologist had also seen this mushroom and already published a description. When he decided the mushroom really was a newly discovered species, he put its description in a book he was writing, "The Boletes of Michigan." He named the new species Boletus eberwhitei in honor of the park where it was first found. The Boletus eberwhitei specimen collected in Eberwhite Park became the type specimen listed in Dr. Smith's description. That specimen now resides in the University of Michigan Herbarium’s Type Collection.
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