Fomes Fomentarius - Ecology

Ecology

Fomes fomentarius is a stem decay plant pathogen. The species' mycelium penetrates the wood of trees through damaged bark or broken branches, causing rot in the host. It can grow on the bark wound, or even directly onto the bark of older or dead trees. The decayed wood shows black lines in the lightly coloured decayed areas; these are known as pseudosclerotic layers or demarcation lines. The lines are caused by enzymes called phenoloxidases, converting either fungus or plant matter into melanin. The lines are not an absolute identifier, as they can also occur in plants infected by Kretzschmaria deusta and some Armillaria species. Despite beginning as a parasite, the species is able to survive for a time (hastening decomposition) on fallen or felled trees as a saprotrophic feeder, and typically lives there for years, until the log is completely destroyed. It is also capable of colonising and breaking down pollen grains, giving it a second food source which is particular high in nitrogen. Infected trees become very brittle, and cracks can occur in the affected tree due to wind. F. fomentarius is particularly adept at moving between cracks on the tree without interruption. However, in addition to the obviously infected damaged trees, F. fomentarius is known to be an endophyte, meaning that healthy trees which are not sporting F. fomentarius fruit bodies could still be infected.

The fruit bodies are perennial, surviving for up to thirty years. The strongest growth period is between early summer and autumn. The yearly growth always occurs on the bottom of the fungus, meaning that the lowest layer is the youngest. This occurs even if the host tree has been laid on the forest floor, which can happen because of the white rot induced by the fungus. This is a process known as positive gravitropism. Very large numbers of spores are produced, particularly in spring, with up to 887 million basidiospores an hour being produced by some fruit bodies. Spore production also takes place in autumn, though not nearly as heavily. The spores are released at comparatively low temperatures. In dry weather, the spores are visible as a white powder.