Fungi of the winter woods

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So back to those itty-bitty mushrooms. The tree was actually the first one my mom and I had stopped to examine the lichen on, and it was fairly unremarkable for the most part. There were little patches of blue-gray foliose lichen up and down the trunk in the first five or six feet from the ground, but nothing that really stood out and grabbed my eye. If this had been the second tree we looked at, after examining the Sugar Maple for instance, I may not have given it more than a cursory glance. It was just by chance that the photographs I took of the lichen on this tree happened to be near a deep crevice in the bark. And at the back of this crevice, with small numbers climbing out and onto the surrounding bark, were these teensy-tiny mushrooms. To give you a better idea of scale, let me post a picture with a reference piece:

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That’s a normal HB pencil. Identifying these little guys was a bit of a challenge. The Lone Pine field guide to Mushrooms of Ontario and Eastern Canada is an excellent reference in terms of providing good colour photos and info on the different species, but it contains 609 species of mushroom and fungus, and these are only just a selection of the most common species likely to be encountered. I couldn’t find a species in the book small enough to be this one, but I narrowed it down to a couple of likely genera, and then did a Google search. I’m reasonably certain the species is Mycena corticola, also called “Bark Mycena” because it grows exclusively on bark, usually freshly fallen or declining living trees. Unlike many mushrooms that grow on live trees, this one doesn’t damage its host, as it doesn’t reach deep enough into the tree to affect the tree’s food transportation system. It’s often found in association with lichen or moss, such as it is here. It is “marcescent”, meaning it has the ability to dry up when moisture is low, and come “back to life” after precipitation or fog. I took the second photo, with the pencil, today and the first photo yesterday, and you can even detect between the two a bit of drying – the mushrooms in the second photo are browner and look a little shrivelled in comparison; I had some difficulty finding a good patch to take the photo of. This may also be in part due to age – they probably came out during the warm spell last week, and the purpleish colour eventually fades to brown as they age.

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Mushrooms are hard to find at this time of year since most of them don’t grow under layers of snow. Fungus, however, is easier to come by. Undoubtedly the easiest to locate in the winter are those large fungal growths that you usually find secured to the side of a rotting stump or log. They’re called “bracket fungus”, or sometimes “polypores” because they have many (“poly”) tiny pores on the underside of the growth to release reproductive spores, instead of the “gills” we associate with mushrooms (what you see when you flip a mushroom over and look at the underside of its cap). I believe the above photo is of Fomes fomentarius, a common and widespread bracket fungus. Its common name is “Tinder Polypore”, after its historical use as tinder for starting fires. If hammered flat it’ll smolder for a long time without much heat, and before matches were invented was often used to transport fire (for instance in nomad societies; in fact, “The Iceman” had a piece of it, along with some flint, in a pouch he was carrying). It was also used as a primitive medical tool and has been shown to contain certain substances, such as iodine, that prevent bacterial growth. It grows commonly on birches, and indeed all the ones I found in the woods were on birch.

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This is another type of bracket fungus, I suspect Cerrena unicolor. One of the frequently mentioned identification features is that C. unicolor is whiteish or brownish in colour but is frequently greenish due to a layer of algae growing on top, which is clearly the case here. This species has an amazing relationship with a couple of wasps, the horntail wasp (genus Tremex) and ichneumonid wasp (genus Megarhyssa). The horntail wasp female carries around spores of C. unicolor in her ovipositor, and when she lays her eggs in the bark of a tree, the spores are deposited with it. The spores begin growing into the bracket fungi in the photo, and in doing so create a large network of fungal “roots” (called “mycelium”), which the horntail larvae feed on during their development. When the larvae pupate, they absorb some of the spores into the pupa, which are then incorporated into the female wasp’s ovipositor during development to allow the cycle to continue. Now, I don’t exactly understand why the fungus does this next part, but perhaps it’s to keep the larvae from eating it out of house and home (the mycelium are its connection to its food source, after all). The fungus will produce a pheromone that attracts ichneumonid wasp females, who come and lay their own eggs. When the eggs hatch, the larvae parasitize the horntail larvae. Whoda thunk all that was quietly going on under those fungal growths?

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 Edit: It’s been suggested to me that this is actually a gypsy moth egg mass, and after looking it up, I think that’s correct. This is one pitfall of identifying something yourself, particularly in an area that’s new to you (like fungi). The description in the fungus field guide was a pretty good match, and the image, although small and difficult to discern details, sure looked like it. Perhaps this is the moths’ camoflauge technique? :) In any case, I’ll leave the text as is, for the information on slime moulds (which should be correct regardless of the identity of the above).

Here’s one last fungus to close off this post. I just happened to spot this blob of creamy brown on the trunk of a tree as I was leaving the forest yesterday. At first glance it looks like someone thwacked the bark with a wet fluffy cattail head, or it might be something a cat threw up (though getting it five feet up a tree would be a feat even for an ambitious cat). It actually belongs to a group of fungi called “slime moulds”, which are fungi that lack the defined shapes we tend to associate with the group. Similar to the fungi that grows on the forgotten leftovers in the back of the fridge, it’s often (though not always) a large blob of roughly uniformly-coloured stuff (for lack of a better word).I’m not sure of the particular species of the above specimen, but there are only some 500-odd species in the world, most of which are very widespread, indicating that, evolutionary speaking, they’re all very old. They have two life stages. The above is the “fruiting” stage, where they produce spores to carry on the next generation. Their first life stage is as a “plasmodium”, a slime (from which they take their name) that is not often seen as it usually resides in rotting logs or other decaying matter. When it comes time to spread their seed, however, they need to move to a better location where the spores can be caught by the wind or otherwise dispersed. The crazy thing is – they move like amoebas, crawling across surfaces to find a good fruiting location, ingesting organic particles in their path and ejecting ones they can’t eat. All at a rate that would make a snail look like a cheetah, however! As a result, they don’t move far, usually just a couple metres at most. And I’ll leave you with this food for thought: slime mould has recently been shown to be able to navigate a maze, connecting two points through the shortest possible distance to food – perhaps an example of primitive intelligence in a fungus?

Winter colours

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Winter is a time of year that most people tend to think of as very monochromatic – whites and grays, perhaps a bit of blue, and maybe some green from the conifers. And, on the landscape scale, this is probably reasonably accurate. However, when you start poking around, you can turn up some fabulous colours. My mom suggested this as a topic for a post, and so we went out this afternoon to do some hunting.

This photo was taken from the Sugar Maple in my parents’ front yard. It’s an old tree, in the twilight of its life. When I was a kid we had a swing made from a tire hanging from one of its sturdy branches, and a treefort high in the fork of its trunk. It was a healthy tree then, without any blemishes or disease. Since then I’ve watched as some branches have died, leaving gaps in its crown that look like somebody’s taken a quick bite for a midnight snack. The bark started flaking in some spots, and the branch with the swing is long gone. And, perhaps the most obvious sign of a tree in decline, its trunk started blossoming in richly-coloured flora.

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Well, not flora, exactly. The growth is actually lichen, which isn’t technically a plant. In fact, it’s not easily classified, because it’s not a single organism, it’s two – a fungus (which is its own type of organism) and an algae (which is a completely different type of organism), partnered together in a symbiotic relationship that benefits both. Although technically the fungus and the algae could live independently, they find it suits them both, especially in harsh or difficult conditions, to partner up so each only has to do half the work. The algae contributes to the partnership by photosynthesizing sugars, much like trees do. It’s the algae that gives lichen its green or blue-green (or sometimes red or brown, depending on the particular type of algae) colour. The fungus, meanwhile, is the house the algae lives in, and it pulls in minerals and nutrients necessary for the pair’s survival.

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There are over 25,000 species of lichen in North America alone. Each species is incredibly well-adapted to a particular niche, and they can coexist easily, as you can see in the above photos. Because of the vast number of species, and the superficial similarity of them all to a human eye, I’m not even going to try to classify any of these to any sort of taxonomic level. It is possible, however, to group them into structural categories. In the above photo, the lime green lichen is considered “crustose lichen” – it’s very short and relatively uniform. The blue-gray lichen is a “foliose lichen”, which tend to be as the name suggests – leafy and broader. A third, which does not appear on this tree but is often seen, is “fruticose lichen” – a three-dimensional lichen that resembles tiny branches or shrubs.

Lichen is incredibly hardy, withstanding temperatures and conditions that would see most other plants perish. It can be found in the deserts where temperatures can reach up to 50oC, or in the arctic where it may drop to -50oC. Because of their low profile, they can grow in windy environments that don’t support tall plant life. They can also survive in areas without much soil, because the fungus secretes an acid that roughens the substrate surface (such as a rock face) to allow the attachment of its root-like tendrils. If anywhere epitomizes harsh conditions, it’s Antarctica, and there are over 350 species identified from this continent alone!

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They take most of their nutrients and moisture directly from the air. Because of this, lichens are especially sensitive to air pollution. It’s been observed that the more pollution in the air, the fewer species of lichen in an area, to the point where in the city centre there’s practically nothing. In London, England, at the start of the industrial revolution, there was so much pollution in the air from coal-fired plants that the lichen on trees in the city completely died, leaving blackened, soot-covered trunks. A moth that was patterned to camoflauge against the trunk suddenly became very obvious to predators. However, an uncommon dark morph blended in well with the new lichen-free trees, and within a short time nearly all of the moth population were dark. When the air was eventually cleaned up lichen returned to the trees, and the moth reverted to its peppered form. Lichen tends to grow very slowly, at about 1mm per year. Some especially dense patches can be dozens, if not hundreds of years old.

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Another old tree in the front yard is a Silver Maple. Although we never played on this tree, it, and its sister a few yards away, have framed the front of the house for decades, and certainly it’s a fixture that I can’t imagine the house without. It must be almost as old as the Sugar Maple, and although it’s retained all of its major branches, the lawn is always littered with small- and medium-sized ones in the spring or after a good storm. Sure enough, when I investigated it had its own patch of lichen along a lot of its lower trunk. There weren’t as many varieties as on the Sugar Maple, I only really noticed two, and one was the same blue-gray type. However, after running off a few shots I peered closer and discovered really, really tiny mushrooms, only 2 or 3mm across, growing amongst the lichen patches!

But that’s a topic for another post. :)