beneath its harmless appearance, a beautiful rot

No fun being part of the scum family. Synonymous in animals with dangerous gangrene, this term is nevertheless, for these fungi, a reason to live. The armillaria is the most impressive witness, specialized in the decomposition of stressed or dead trees. A difficult but essential job that only saprophytic (rot-eating) fungi are capable of carrying out. If trees know how to soar vigorously towards heights, it is thanks in particular to lignin, a molecule which strongly permeates the walls of their cells and their vascular interstices. An accumulation which gives them strong mechanical resistance and protects them from bacterial activities.

Lignin, however, has a drawback: it contains phenol, which is toxic in its free form. But as it has managed to neutralize this toxicity, it allows plants to benefit from it. And this is where the armillaria comes in. Often grouped in clumps on stumps or at the base of trunks, these orange or lemon-yellow mushrooms are the main agents of the transformation of trees into humus, or humification. Patiently, they return the giants of the peaks to the earth, transforming them into nourishing soil for a multitude of small organisms. This very ancient knowledge of armillaria is perhaps at the origin of the end of the accumulation of plant debris on the planet, 280 million years ago. Debris which, until then, had been transformed into coal. Since then, this major producer of humus has become more comfortable. To the point of sometimes constituting enormous specimens. In a forest in Oregon (United States), one of them extended, through its underground branches, over nearly 10 km2. We may be scum, but we are nonetheless on the side of the champions.