Fungi play an essential role in the ecological functioning of forests. Most of them are saprophytic species that act by breaking down the plant and animal organic matter and enriching the soil and incorporating nutrients into the food chain. Others are symbionts and are associated with the roots of certain plants form mycorrhizae, allowing these vegetables to live in certain media, such as poor or waterlogged. Therefore, the conservation of fungi is essential for the preservation of forests and their own habitats.
In spring and, especially, in autumn, fruit bodies (mushrooms) of all shapes and as colorful as possible, grow into the slopes of the Sierra de Guadarrama. However, it should be kept in mind that the collection of fungi is subject to specific regulations.
The saprophytic fungi are more abundant in the forests than in other habitats, as result of these environments optimum ecological conditions. in relation to their physiological requirements. In the National Park and its peripheral area, there is an important forest area with masses of different species trees, then the presence and the variety of these fungi is important.
Throughout the year, most of the fungi groups develop in the pine forests of Scots pine (Pinus sylvestris), which are dominant forest mass in the Park. The most well-known and abundant belong to the groups forming “mushroom” bodies (Ascomycota and Basidiomycota), producing spores. During the spring appear, among others, species of the genus Gyromitra and Morchella. The summer, if conditions have been favorable, is time to grow for species in the genera Russula and Boletus. In autumn the diversity is maximum, with species from a wide range of groups, some of them very showy, among which we might emphasize Amanita muscaria, Amanita rubescens, Boletus edulis, Boletus pinophilus, Clitocybe odora, Fomitopsis pinicola, Lactarius aurantiacus, Lactarius deliciosus Lycoperdum perlatum, Mycena seynii, Ramaria formosa, Russula spp., Sarcodon imbricatus, Sparassis crispa, Suillus luteus, etc. but we can also observe fungi of these groups very striking that do not make mushrooms, as Tremella mesenterica, or some other groups very different in terms of phylogenetics, although traditionally studied next to fungi, such as the mixomicetes Lycogala epidendrum and Leocarpus fragilis.
In the Pyrenean oak groves and the mixed forests with Albar pine, grow some of the above species, in addition to Amanita citrina, Amanita phalloides, Boletus aereus, Entolom alividum, Laetiporus sulphureus, Macrolepiota procera, etc.
The National Park has other very interesting forest habitats. One of them is the birch (Betula pubescens subsp. Celtiberian) woods, where has been detected the presence of a unique set of species of fungi (Leccinum scabrum, Lactarius torminosus, Lactarius necator, Piptoporus betulinus, etc.). In addition, there are other enclaves more clear in the forests in lower areas, where they develop certain heliophilous species that form the famous "witches circles", which are circles of edible fungi.