Glossary terms on this page - mushrooms | mycorrhizae
| for•est [ˈfôrəst] a large area covered chiefly with trees and undergrowth. e•col•o•gy [iˈkäləjē] the branch of biology that deals with the relations of organisms to one another and to their physical surroundings. ========== Mushrooms are the fruiting bodies of much larger underground organisms. The 
mushroom itself is similar in function to an acorn produced by an oak
tree. The
mushroom emerges from the soil like an acorn from the branch of an oak tree, and just as the acorn is filled with stored energy
to assure a strong beginning, the mushroom bears spores, the fungal equivalent of acorns.
Literally billions of spores are produced, floating everywhere through
the forest air.Evidence of this can be seen by the large variety of fungi that appear seemingly out of nowhere on cheeses or bread. The mushroom is just the tip of the iceberg - meaning that the oak tree itself is more grand and complex than the acorn it produces. In the case of fungus, the "tree" is known as mycelium. The mycelium is present under the ground, year-round, and is only revealed by the occasional seasonal appearance of mushrooms - both above-ground fruiting mushrooms and below-ground fruiting mushrooms. These underground organisms we call mycelium can be huge, covering square miles and growing up to an inch daily. If you could see this mycelium it would look somewhat like a dense underground spider web covering the entire forest floor. These large mycelial "spider webs" survive in essentially two ways: (a) by decomposing dead organic matter like logs, stumps, and litter (b) by forming a symbiotic relationship with living plants and trees. Vegetation is broken down by the mycelium and converted back into rich compost. Although the mycelium is microscopic, it can be detected by the presence of 
mushrooms and its actions can be observed by watching a
log or stump rot, becoming softer and smaller annually.
Ground-based mushrooms exist in a symbiotic relationship with living
plants and trees. This relationship is called mycorrhizal, which means
literally “mushroom root hair” or "fungus roots".
Ectomycorrhizal is really the proper term we should be referring to
here, as these mycelium attach to the outside of rootlets (The only
other type of mycorrhizal relationship with plants is
called arbuscular, or endomycorrhizal, where penetration of the
cell walls of the rootlets is accomplished, but this is not under
discussion here). Many plants and
trees form a symbiosis
with at least one if not many kinds of fungi. You can't have
fungi
without trees, and you can't have trees without fungi. As the
spider-web-like mycelium spreads out across the forest floor it
actually surrounds the rootlets of trees and often attach to the roots
of
vascular plants connecting them not only with each other, but also with
the
entire forest floor. These organisms can cover square miles of forest floor and there can be up to one mile of microscopic mycelia strands in one centimeter of soil! When rain comes to the forest, it soaks into the soil and passes through this fungal sieve. The mycelial web acts as a filter absorbing nutrients and moisture, which can be utilized by the forest's plants and trees. The mycelium then becomes a kind of "underground superhighway", carrying nutrients and moisture to plants and trees from areas beyond the reach of their rootlets. The mycelial web can expand the absorption area of roots significantly. In turn, the mushrooms are gaining sugars and nutrients produced by plants and trees during photosynthesis. This is what we call a symbiotic relationship, where each organism profits from the shared association. Northern Flying Squirrels And Below-Ground Fruiting Fungi  You have all probably heard the term "web of life", and that in nature, everything is connected in some way. These connections create a balance. Some of these connections are obvious to the average observer. Many are not. The more you study plants or animals, the more connections you will find. There are many, many connections that remain undiscovered - the young naturalists of today will be identifying many new connections, as scientists, in the future. Studying small, nocturnal, tree-dwelling animals is a special challenge. Up until a few years ago, no one had made the connection between flying squirrels and underground fungi. First Nations people believed flying squirrels ate dirt, and it was their custom not to eat animals that ate dirt. But what flying squirrels were really doing is simply digging in the dirt to find their favourite food - truffles! It was once thought by the scientific community that flying squirrels spent all their time in the trees. Scientists wondered why the remains of northern flying squirrels, nocturnal, tree-cavity-dwelling small mammals, were being found in the stomachs of foxes and coyotes, predators that aren't great at climbing trees (they can't!). The answer: land predators catch the flying squirrels as they roam the forest floor looking to dig up and eat their favouite food - stinky, smelly truffles. Truffles are the “fruit” of certain fungi. Fungi of one sort or another surround us, providing life-saving antibiotics, coaxing bread to rise, cheese to ripen and beer to ferment. Some fungi fruit above ground, like your typical mushroom that you see at the grocery store or during a walk in the forest in the Fall. Many fungi in the forest, however, fruit under the ground, and you never see them at all. But flying squirrels have great noses and can located these fruiting fungi buried in the soil by their smell.  Fungi also play an essential part in sustaining the health of the forest ecosystem. Fungi are like large-scale recyclers. They are the great decomposers, able to break down not only cellulose but also lignin, a main component of wood. Even termites and other wood-eating insects depend on fungi and bacteria in their gut for decomposing otherwise indigestible compounds. More Connections For owls, these underground-fruiting fungi act as the great matchmakers, safeguarding the health of old-growth forests that the owls call home and attracting the attention of flying squirrels that the owls call dinner. The fungi allow for the easy transfer of water and nutrients to the tree roots. The trees produce sugars that feed the roots that feed the fungi. The fungi produce these truffles. The truffles are eaten by the flying squirrels, which, in turn, are eaten by the owls. The owls don't just use the trees for a place to perch. Those trees are also sending energy into another part of the ecosystem that directly connects back to the owl. How It All Works Fungi are present in all forest soils. This fungi grows really long, microscopically thin filaments that surround the tree's rootlets in a "cottony web” or “sheath". The fungi’s web-like filaments, or mycelium  , attach to the tree
rootlets on a cellular level, and literally become part of the tree's root system. So, in a way, the
fungi become the tree's "drinking straw".
The fungi also "fix" nitrogen and phosphorous (nutrients that are bound
up in the soil in forms the trees can't readily use) so that they then can
be used by the tree, and transfer this easier-to-eat food to the tree.
The "sheaths" act as a storage area for those nutrients and help the
tree's defend themselves from soil-borne pathogens (pathogens are things
that cause
disease).
What's in it for the fungi? Food! They depend upon the tree to supply
them with a supply of the vitamins, sugars, starches and carbohydrates
the tree produces during photosynthesis.Where The Northern Flying Squirrel Fits In Meanwhile, in the past 20 years, scientists have learned more about the integral role of flying squirrels and certain other small mammals in the forest food web (another animal that loves to eat underground fungi is the red-backed vole). Scientists have looked into the stomachs of flying squirrels and picked through their droppings, trying to analyze their diet and identify fungus spores. We've fitted them with radio collars and even used night-vision goggles to track their feeding habits. Above-ground mushrooms possess fruiting bodies that scatter spores by wind, or when they are jostled by an animal walking by. But truffles, which don't emerge from the forest soil layer, require a different method to ensure the dispersal of their spores. As these potato or rock-shaped truffles mature, their odour intensifies. Some smell like garlic. Others smell like tar. Some even stink like, well, poop! Gross, but this pungent odour is necessary. It's sort of like a smoke signal, or better yet, a stink signal, that says "please come and eat me"! The flying squirrel locates the truffle by sniffing the earth under the trees. It then digs up and eats the truffle, and the spores, which remain “viable” throughout the digestive process, are “pooped out” later by the squirrel, often in a different part of the forest patch, or in another forest patch altogether. Flying squirrels, especially males, can travel 5 kilometres or more in one evening! A fecal pellet is more than a package of waste products - it contains four components of importance to the forest: (1) viable spores of mycorrhizal fungi; (2) yeast, which is a part of the nutrient base, has the ability to stimulate both growth and nitrogen fixation in the bacteria, and may also stimulate spore germination; (3) nitrogen-fixing bacteria (and the entire nutrient requirement for nitrogen-fixing bacteria); and (4) an "antifreeze" that protects the spores during the cold of winter, without which the bacterial cells would rupture and die when feces deposited during winter thawed in spring. Once these droppings reach the forest soil, the microscopic fungal spores begin to grow their own mycorrhizal webs, attaching themselves to the rootlets of trees and plants in the immediate area. Eventually, these mycorrhizal bodies mature and develop new stinky truffles, and the whole process starts all over again. All animals are mindful of how much energy they expend looking for and storing food. For example, have you ever watched chickadees or nuthatches at a birdfeeder? If you watch closely, you’ll notice that they don’t take just any old sunflower seed. They may pick one up and throw it away. Pick up another one, and throw that away. They aren’t being wasteful, at least not on purpose! They just want the heavier seeds, which have more energy contained within them, so that the energy expended looking for a “hiding spot” or cache will be worth the effort involved! Flying squirrels don't glide or scamper down the tree to dig up just any old truffle. Scientists believe the squirrels seek out truffles with higher-calorie oils and more nutrient value, and those varieties just happen to be the stinkier ones. It's Not Just Flying Squirrels! Many other forest mammals chow down on below-ground fruiting fungi. Bears, deer, elk, and most small furry forest critters love to chow down on these false truffles as well. Red-backed voles are especially mycophagous - some species ONLY eat below-ground fruiting fungi! A lot of forest mammals, including flying squirrels, eat regular (above-ground fruiting) mushrooms too. So the next time you have mushrooms with your dinner, a flying squirrel or other forest-dwelling mammal in a forest near you might just be having them for dinner too! Coarse Woody Debris (CWD)
 Coarse woody debris is defined as "sound and rotting logs and stumps, and coarse roots in all stages of decay, generally greater than 3 inches in diameter, that provide habitat for plants, animals and insects, and a source of nutrients and structures for soil development" (Stevens, 1997). A much overlooked area of forest ecology is the importance of downed wood and 
CWD. A huge old tree is felled by a lightning strike. The resultant
fallen log becomes a home for a huge assortment of invertebrates such
as beetles, ants, isopods and centipedes. They help break down the cell
structure of the wood, which in turn allows fungi and nitrogen-fixing
bacteria to establish a foothold. Small mammals such as the flying
squirrel and red-backed vole dine on the fungi produced from this
"nurse log".  Other
animals such as snakes, salamanders, mice, shrews and worms utilize the
log as a home or refugia. The log, after time, becomes punky and
sponge-like. This allows it to "hold" a large amount of moisture,
which, in times of drought or dry season, is slowly released into the
surrounding soils, providing much-needed water for the root and
mycorrhizal systems of surrounding flora (seedlings, lichens, mosses,
etc.) and fungi, which in turn help decompose the log further. Should a
forest fire ravage the area, many small arthropods survive, hidden
under the safety of an old, moisture-soaked downed tree. CWD also
provides a starting ground for many species of conifer trees,
especially in older-growth forests, where competition for growing space
is fierce, and add a significant amount of organic material to the
forest soil.Plants in the wintergreen family, such as Indian pipe, pinesap, and sweet pinesap have symbiotic, mycorrhizal relationships. A common fungus associated with these plants is an Ascomycete that forms a subterranean structure commonly called a "deer truffle". There is also a small genus of orchids, called coralroots, that obtains the majority of its nutrition from a mycorrhizal association with soil fungi. |