MUSHROOMS AND THE ENVIRONMENT

adapted with permission from
"The Magic World of Mushrooms"
© Ron Russo
retired Chief Naturalist
East Bay Regional Park District

All photographs by
Ranger Chuck Bancroft

forms, size and color  |   growth of the mushroom  |  spores, wind and water
mushrooms and other animals  |  the web of life

Past History

For hundreds of years mushrooms have excited both the minds and stomachs of millions of people. They have been used for food, medicine, religious ceremonies, and for poisoning enemies. Mushrooms have been an important part of many cultures around the world. In California some Native Americans have made soups out of shredded mushrooms. The Indians collected fresh specimens, dried and then shredded them before storing the fungi for later use. Fresh mushrooms were boiled and added to acorn soup. Occasionally when a person became ill after eating a poisonous mushroom, an antidote was made by boiling dried deer brains in water and drinking the greasy broth. This was the Native American's way - survival through the use of whatever resources were at hand, including those plants we call mushrooms.

For thousands of other people, winter is an exciting time when "rainy season people" are out searching for nature's jewels, mushrooms and other fungi. The colors, shapes, smells, and curious habits of mushrooms have provided endless hours of study for devoted fans. From painting, photography and microscopic study, mushrooms have given us a better understanding of our complex environment.

Forms, Size, and Color

Mushrooms will display an infinite variety of size and color. While out in the woods you will discover mushrooms growing side by side that are both grotesque appearing and artistically very pleasant. Mushrooms vary from pinhead in size to basketballs. The colors of mushrooms include all the colors of the rainbow.

The typical mushroom has a stem with a cap on top, and yet other fungi can look like a bird's nest, lumps of jelly, volleyballs, ocean coral, and stars. Because of their general shape and the type of spore-producing structure, mushrooms have been placed in certain categories. These include gill fungi, tube fungi, shelf fungi, cup fungi, coral fungi, jelly fungi, saddle fungi, and stomach fungi.

Mushrooms form a part of the ecology of a forest or grassland. They are dependent on the same limiting factors that influence the trees, grasses, animals, insects, and birds found in any habitat. Each depends upon or is influenced by a wide range of factors including wind, rainfall, temperature, and other organisms. Each factor forms a single strand in the web. These strands and their relationship to the web are called "ecology."

Growth of the Mushroom

The mushroom that we see is actually the fruiting body of the hidden growth. This growth consists of microscopic filaments (hyphae) which combine to form white or yellow strands called mycelium. The mycelium grows in the soil on wood and leaves, beneath the bark of dead trees, and within the heartwood of living trees.

The mushroom first develops as a tiny bead on the mycelium and then increases in size, passing through the button stage to its mature size. The lifespan of mushrooms is different from species to species. Some last only a few days, developing, maturing, releasing millions of spores, and then disappearing; others can last for several weeks, and some bracket or shelf fungi last for years.

All species of fungi have specific requirements of moisture and temperature before they will produce a fruit. Some mushrooms have a very restrictive set of requirements while others have very broad sets of requirements. Even under the proper climatic conditions, mushrooms may not develop if the mycelium lacks the necessary food energy. Many fungi will not fruit for several years; then one year when everything is just right, the woods will seem full of them. Other fungi with a broader range of temperature and moisture requirements appear annually. During a year with heavier than normal rainfall, the usual mushroom crop may be depressed. However, there are mushrooms that require extremely wet conditions for normal growth. Like lettuce and other household vegetables, about 90% of a mushroom is water.

While some mushrooms do appear in the spring and some in fall, the majority of mushrooms come during the rainy months of November through February. Unlike green plants, mushrooms lack chlorophyll and are unable to produce their own food. Mushrooms depend upon both living and dead organisms for food. The mushrooms that feed on living organisms are called parasites, and those that feed on dead organisms are called saprophytes. Most mushrooms are saprophytes.

When feeding on materials, the mushroom through its enzymes breaks down the organic debris and thus replenishes the soil with nutrients. Mycelial threads decay or digest the food they eat with enzymes just as our stomachs digest food we eat. As a mushroom decays, most of its food energy returns to the soil. Ammonia is released by the mycelium and is in turn acted upon by other bacteria which help convert it to usable nitrogen, one of the most important elements used by plants.

A great disservice is done if mushrooms are labeled only as destroyers. In the economy of a forest community, mushrooms are important soil enriches and necessary agents of decay. If we think of trees and shrubs as continually removing nutrients from the soil and locking them up in branches and leaves, then we can see what would happen without something to reduce dead debris and thus replenish the soil.

Various species of mushrooms are found under certain kinds of trees and shrubs. Various species of Boletus, Russula, Lactarius, and Amanita mushrooms can be expected to appear beneath the Monterey pines each rainy season. Some mushrooms tend to occur in a variety of habitats, but many are restricted in distribution. Scientists have discovered that the mycelium of a number of species surrounds and often penetrates the roots of host trees while ignoring other tree species nearby. This fungus-tree relationship is called mycorrhizal. This results in a more efficient nutrient-absorbing tool. In some natural situations where the soil is not highly fertile and the fungus does not develop, conifer seedlings often show signs of nitrogen starvation and ultimately die. The continual rain of leaf and branch material to the forest floor provides an inexhaustible supply of food to ground-dwelling fungi. Unlike those fungi that live on logs and ultimately die when the food runs out, the mycelium of ground-dwelling fungi can live for centuries in the general area of its birth.

Spores, Wind, and Water

Besides the beauty of a mushroom's form and color, which is visible to the naked eye, another kind of beauty exists at the microscopic level. The size, shape, and color of mushroom spores are important clues to the serious student of fungi who wishes to identify a fungus.

Spores occur in a wide variety of colors black, brown, pink, white, lilac, and even green. Each species of fungus has spores of a characteristic color. The mushroom spores are borne on partially or fully exposed surfaces like gills, tubes, and teeth, or even on the inside of cups. If you look closely with a microscope, the oddly-shaped spores may remind you of a fruit, vegetable, a piece of candy, or a Christmas ornament.

All members of the plant kingdom face the problem of the continuance and dispersal of their species through seeds or spores. In studying the web of mushroom ecology, we discover that wind, water, insects, slugs, squirrels, and deer assist in the dispersal of fungi by transporting spores. During development of a typical gill mushroom, the cap generally orients itself so that the gills remain vertical.

This allows free downard passage of the spores. Because of the small size of the spores, the slightest breeze gathers thousands from a ripe mushroom and transports them to far-off places. After liberation, most of the millions of spores produced perish. A few reach favorable locations and germinate under proper conditions of temperature and moisture. The value of wind as a dispersal mechanism is proven by the fact that mushroom spores have been collected several miles above the earth. The very air you are breathing is full of mushroom spores, but don't fear - your lungs are hardly a favorable place for mushroom growth.

Drifting down from high in the sky, rains pick up and transport spores along branches of trees, while other rainwater moves spores around on the forest floor. But the meaning of a single raindrop goes much further than just transport. It has been discovered that heavy drops of water actually cause some fungi to release their spores. In fungus like the Earth Star (a puffball or stomach fungus), the force of a raindrop can break the papery thin sheath and force a cloud of spores to be released with each raindrop. Animals, insects, wind, and rain all help disperse the valuable spores.

Mushrooms and Other Animals

A variety of creatures, big and small, turn to mushrooms for food. Animals as well as insects are a very important part of mushroom ecology. Black rove beetles, often found among the gills, hunt for the larvae of flies. Gnats and flies lay their eggs on mushrooms, and the larvae work their way into the fungus to devour it. Flea-like insects called springtails, live within the larval tunnels and the gills of mushrooms. They are in turn fed upon by centipedes.

Banana slugs move ever so slowly across the forest floor and feed on all types of plant material. In spite of its huge appetite, the banana slug often leaves the fungus half-eaten or dotted with craters.

The winter diet of squirrels is supplemented with fungus. Their acute sense of smell helps them detect mushrooms that remain hidden beneath leaves and branches. Woodpeckers hollow out nests in old trees decayed by the activity of such fungi as shelf fungus. The woodpeckers in turn gather spores in their tail-feathers which are used as props against the bark of the tree. The spores can be rubbed off later on an uninfected tree and help begin the cycle all over. Old holes drilled by woodpeckers in search of food provide an easy way out for developing mushrooms, which follow the lines of least resistance.

During winter months the blacktailed deer will feed on fungus as well as acorns and palatable leaves in forests and meadows. Cows sometimes ingest spores with the grass they eat. The mushroom flesh provides some nutrition for the animals, but many spores will pass unharmed through their digestive tracts. In some mushrooms, before the spores become capable of germinating, they require temperatures and chemical conditions similar to those found in the stomachs of deer. Deer can be an important part of the dispersal and development of some fungi.

The Web of Life

In this intricate yet fascinating world of mushrooms, we have seen how light and water, how trees and soil, and how insects and mammals combine to produce the web of the ecosystem. Perhaps we begin to see that the story of mushrooms is but one minute part of the web of relationships that cover the earth.

Our journey into this kingdom need not end here, but may continue with you as a lifelong hobby. We hope that the next time you discover a colorful mushroom in the Reserve you won't give it a scuff of the foot, but that you will look at it as did Thoreau .

"as an expression of an idea, growth inspired and appropriated by spirit."

Click Here to learn about The Fungi of California.

All photographs by Ranger Chuck Bancroft unless otherwise noted