Although perfectly adapted to the forest environment, fungi and species of mould and yeast constitute of group of organisms quite separate from all others. For biologists, they are neither plants nor animals. While they often live attached to the ground like plants, they feed in a way similar to that of animals. Fungi do not carry out photosynthesis, nor do they draw their food from the dead matter of other living beings; fungi survive thanks to a mass of filaments called the mycelium.
Although often overlooked, fungi are among the largest living organisms. In a forest, one mycelium alone can spread through the soil over dozens or even hundreds of hectares. What we see on the surface of the ground, a small hat atop a foot, is only the reproductive organ, a tiny part of this strange living thing.
Mycelia are omnipresent in the soil, where they participate, along with bacteria, termites and beetle larvae, in the decomposition and recycling of dead leaves and branches. They secrete enzymes that digest or deteriorate the most solid organic matter – wood, for example. They absorb and filter water and agglomerate solid particles, thus contributing actively to the forming and building of the soil. They are indispensable to the good health of the forest.
Certain fungi, namely mycorrhizae, play a little known role. Attaching themselves to tree roots, they form a symbiosis with the trees, exchanging resources. The trees supply them with food, in return for which the fungi protect their roots and facilitate their absorption of nutrients in the soil. Conifers, which often grow in poor soil, could not thrive if they were not assisted by these fungi.
The diversity of these microorganisms is astonishing. Scientists have identified over 75,000 species to date, but over a million probably await discovery.
Extrait du livre « Des forêts et des hommes » rédigé par la rédaction de GoodPlanet à l’occasion de l’année internationale des forêts et disponible aux éditions de la Martinière.