Fascinating Fungi

by Irene Palmer.

Hoof Fungus, Fomes fomentarius, on Silver Birch.

Many fungi are responsible for wood decay. Since fungal spores are produced in vast quantities, there are always plenty available to colonise wood when the bark is damaged, when a tree is felled or branches fall to the ground.

Some of the first invaders are usually the moulds which favour sawn or broken surfaces. A succession of fungi carries out the process of decay and some prefer live standing frees; they're the destructive parasites which invade the sapwood.

Bootlaces of Honey Fungus, Armillaria species, under the bark of a fallen tree.

Thankfully there aren't too many and they often occur when a tree is stressed, often by drought. Honey fungus is feared by foresters, fruit growers and gardeners, who look out for telltale 'black bootlaces' under the bark near the ground.

Others attack the heart wood and aren't true parasites because they hollow out the tree and don't kill it. Some fungi limit themselves to particular species of trees.

Most fungi found on fallen wood are saprophytes and give no cause for concern. The Green Oak Fungus is one of the prettiest; this cup-fungus stains wood a greenish-blue and produces the 'green oak' that has been much sought after for marquetry and treen, especially where it has been used for Tunbridge Ware.

Turkeytail, Trametes (or Coriolus) versicolor.

The soft-rot fungi follow the initial saprophytes, attacking the outer layers of the wood, penetrating the cell walls and weakening it. Brown rot and white-rot fungi carry out the next stages of decay. The former digest the cellulose in wood, turning it a reddish colour in the process.

The white-rot fungi have a more powerful effect as they can digest both cellulose and lignin. The Zoned Fungus (Coriolus versicolor) is particularly efficient in unlocking chemicals in wood.

Magpie Ink Cap, Coprinus picaceus. Farningham Wood, October 2011.

A succession of insects accelerates the decay process. The mechanical damage they cause exposes new surfaces to the activities of fungi. Bark beetles are often the first arrivals and bore into the wood, followed by cardinal beetles then woodlice.

Tiny springtails chew the disintegrating wood into smaller pieces. The larvae of stag beetles, rare cockchafers and click beetles are particularly fond of decaying wood, whose biodiversity value is enhanced by plants such as mosses, ferns and lichens.

Myxomyxetes, commonly called slime moulds, are a group of organisms found all over the world, especially on fallen logs. For part of their life they adopt primitive animal-like feeding habits and form a slimy plasmodium that moves amoeba-like over the wood. They're quite harmless because they feed on fungal spores, bacteria and yeasts and are often attractively coloured. They can travel a metre or more when conditions are moist.

The tiny crimson loofahs of Arcyria incarnata, the golden goblets of Craterium minutum, the feathery tufts of Stemonitis axifera or the iridescent Lamproderma scintillans are nature's surprisingly beautiful living legacy in the final stages of decay.