Friday, 4 March 2011

Some robust fungi

When you think of fungi you tend to think of the soft fruiting bodies evident throughout the autumn months, the mushrooms and toadstools of grassland and woodland. Yet there are fungal fruiting bodies that are more robust in nature and which can be seen throughout the year. Included in with these are the bracket fungi, hoof or plate-shaped structures that emerge at right angles from the vertical trunks of standing timber or from fallen wood.

Bracket fungi are seen by some as parasites and the destroyers of wood, but this attitude misses the point and devalues the valuable role that fungi play in the recycling of nutrients. The brackets themselves are the fruiting bodies, the only external evidence that a fungus is present within the timber (much as mushrooms and toadstools are the visible component of fungal systems lurking within the soil, leaf-litter and underground root systems of plants and trees).

The bracket is the means by which the fungus can distribute its fungal spores to colonise new sites. In order to gain access to these sites, the spores will typically have to gain entry through the protective bark, perhaps through a wound. As you can imagine, the chances of an individual spore, distributed as they are by the vagaries of the wind, encountering a suitable wound are remote. This is why so many spores are produced; for example, it has been estimated that a large Ganoderma bracket fungus might produce a staggering rain of some 20 million spores per minute steadily over a period of five months!

Many bracket fungi are associated with particular tree species – the already-mentioned Ganoderma species on Oak and Beech, for instance. Most trees in their middle and old ages probably host bracket fungi and some or our oldest trees support particularly scarce and localised bracket fungi. In these trees you often find that the fungal decay hollows out the heart wood, the living sapwood being confined to a narrow region between the decaying interior and the bark. Being hollow can be advantageous to an old tree since it lightens the load, reducing the amount of heavy deadwood, and increases the tree’s flexibility when it is windy. Interestingly, it was the younger-aged trees that were hardest hit by the 1987 gale in many of our oldest woodlands, the hollow cylinder trunks of the older trees better able to withstand the conditions.

The fruiting bodies of most bracket fungi are pretty solid and so it is unsurprising that few are deemed edible or worth the effort (though Sulphur Polypore was a faddish exception in the nineties, featuring in certain gourmet restaurants). Their robustness is part of their appeal, marking them out from the ephemeral mushrooms and toadstools.

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