The importance of fungi in forest ecosystems

The importance of fungi in forest ecosystems

Science

The harvesting pressures that certain mushroom species are subjected to, as well as improper practices resulting from uncontrolled human intervention in ecosystems, along with climate change and the negative effects of current pollution, are affecting the extinction of fungal species and altering fungal communities. Redlisting is one of the main tools used to alert environmental managers and policymakers to action in this regard. And the fact is that the importance of fungi in the forest ecosystems of our natural environment is enormous to such an extent that it is closely related to the survival of plant masses with all the ensuing consequences. Fungi play a fundamental role in the functioning of ecosystems, mainly due to their trophic characteristics. Thus, by studying the different life forms of fungi and the way they feed, we can see their importance in nature. Mushrooms can be:

Symbiotes

They are all capable of creating symbiotic associations with plants that share their habitat, creating the so-called mycorrhiza (a term first used by the German botanist Frank in 1885), an association at the root level that is beneficial to both creatures, since although the fungus helps the plant absorb water and nutrients such as phosphorus and nitrogen, it receives in return carbohydrates formed in the process of photosynthesis. It was found that from 85% to 95% of vascular plants form mycorrhiza, which can be of the ectomycorrhizal type (from 3% to 5% of the total number) or endomycorrhizal type (the rest). In the first case, fungal hyphae cover the walls of plant root cells without penetrating inside, and in endomycorrhiza –

The importance of ectomycorrhizae in the forest environment is enormous as they establish associations of this type with trees and shrubs of important families such as Pinaceae, Fagaceae, Betulaceae and Salicaceae, among others. On the other hand, ectomycorrhizal fungi are part of such genera widespread in our mountains as Amanita sp., Boletus sp., Lactarius sp., Hebeloma sp., Tuber sp., Terfezia sp. Etc. These mushrooms are of great economic interest because they are highly prized for human consumption (as is the case with banknotes, chanterelles, truffles and ground potatoes).

The practical application of ectomycorrhiza in forestry can be focused either on the cultivation of mycorrhizal plants for afforestation of problem areas, or on the cultivation of mycorrhizal plants with fungi of commercial interest, as in the case of mycorrhizal oak trees with truffles.

Vesicular-arbuscular. They appear on most shrubs and herbaceous plants, tropical species, some temperate trees (eg maples and ash trees) and almost all cultivated plants. The fungi that form this type of mycorrhiza belong to the order Glomales. These fungi are strictly symbiotic; they cannot develop without a host, unlike ectomycorrhizal fungi. Plants with this type of association are widely used for reforestation in drylands where plants are under severe water stress.

Erikoides. They appear on plants of the order Ericales, heather associated with fungi of the department Ascomycota. They are characterized by the presence of intracellular hyphae in the form of a corkscrew and are very effective in absorbing nitrogen and increasing the resistance of plants to the toxicity of heavy metals, which has already been used in the restoration of contaminated soils.

Arbutoids. They are exclusive to some plant genera of the order Ericales (Arbutus sp. And Arctostaphylos sp.) And are associated with both fungi of the divisions Basidiomycota and Ascomycota. They present intracellular hyphae in a corkscrew shape, but also appear in the intercellular spaces as a Hartig’s network.

The presence of mycorrhizal fungi in a forest is not only a direct benefit to the plants that inhabit it; in addition, mycelial networks extending to the surface horizons of the soil improve its structure and productivity, ensuring stability and resistance to any disturbance.

Saprophytes.

These mushrooms feed on substances formed during the decomposition of dead organic matter (both plants and animals), therefore, together with bacteria, they participate in the processing of our mountains. To do this, they use enzymes that can break down complex carbon sources such as cellulose, lignin or starch and convert them into simple and nutritious molecules such as sugars and amino acids. While some fungi implicitly use organic matter of different origins, others prefer more specific substrates. Thus, among other things, we find:

Lignicultural fungi that grow on dead wood, such as Fomes fomentoius (L.) Fr. and Agrocybe aegerita (V. Brig.) Singer.

Growing of meadow mushrooms such as Volvariella speciosa (Fr.) Singer or Macrolepiota sp.

Humicultural fungi that develop in humus or mulch, such as mushrooms (Agaricus sp.), Coprinus lagopus Fr. (Fr.) and Entoloma lividum Quél.

Strobilized fungi that grow on pineapple and other fruits such as Mycena seynii Quél. and Baeospora myosura (FR) Singer.

Dung coprophilous fungi such as Panaeolus semiovatus (Sowerby) S. Lundell & Nannf. OR.

Fungi that develop on animal bones, such as Onygena equina (Willd.) Pers.

Decomposition is a long-term process, and without the activity of saprophytic fungi, biomass will accumulate and the functioning of ecosystems will be disrupted. Some of these mushrooms are also the best-selling mushrooms in the world, such as Parisian mushroom (Agaricus bisporus (JE Lange) Imbach), paca mushroom (Pleurotus ostreatus (Jacq.) P. Kumm), thistle mushroom (Pleurotus eryngii (DC.) Gillet) or shiitake (Lentinula edodes (Berk.) Pegler).

Parasites

These fungi are characterized by living in different hosts, causing more or less serious damage or even death. If they cause disease in the host, they are called pathogens. Some need to live off living cells (biotrophic), while others are able to continue to intelligently decompose organic matter after the death of the host (necrophytic fungi). Parasitism is a response to the existence of natural biological control. These fungi play an important role in ecosystems, acting as balancing factors for them and influencing the competition between plant species. They promote diversity by causing changes in the size and distribution of plant species. However, in monospecific forests, these fungi can cause serious damage to stands. An example of this type of mushroom,

conclusion

Every day, human intervention in the natural environment is increasing, changing the habitat at will. Fungi, like other biotic groups, suffer from the consequences of this human activity, both directly due to inadequate collection of carpophores and destruction of their habitats, and indirectly due to infection. Various types of fungi perform a large number of ecological functions that increase the resilience of ecosystems. Thus, they are excellent indicators of the state of conservation of our forests, and it is very important to maintain a wide variety of habitats in order to promote their growth and reproduction our green spaces.

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