Mushrooms as a bioindicator of the health of our forests

We are in autumn, a time of leaf fall and the traditional mushroom picking, a growing hobby that attracts the attention of more people every day, who are looking for very seasonal and ephemeral delicacies. But beyond gastronomic or economic interest, we need to know that mushrooms are the fruiting body of fungi (such as the fruit of the tree), which play an important biological function in forest ecosystems, since, among other things, they are capable of acting as decomposers of accumulated organic matter or of establishing a symbiotic relationship with plants, which makes our forests more resilient.

In the Carboniferous period (about 360 million years ago), plant matter accumulated and fossilized in layers or strata, producing carbon. The appearance of fungi capable of decomposing lignin in plants ended the formation of this sedimentary rock and the massive accumulation of plant matter some 60 million years later. They were the first decomposing fungi or saprophytes.

The mushrooms saprophytes they are capable of decomposing dead plant and animal organic matter, of enriching the soil of our forests with the nutrients resulting from their recycling action, an important task that benefits all living organisms directly or indirectly.

A forest or ecosystem in which these fungi are abundant would be indicative of the accumulation of organic matter.

In addition to fungi that break down dead matter, there are others that colonize living organisms in order to feed or live at the expense of them. They are the parasitic fungi, those who take advantage of any weakness or injury to enter the organism in which they are going to live and to which they can cause illness and even death.

A forest or ecosystem with an excessive presence of these fungi could indicate that it is in decrepitude, with old and sick plants.

Finally, there are fungi that establish relationships with other living beings in a symbiotic way, with the objective of being able to benefit both organisms and achieve something that they could not achieve on their own. The most well-known and outstanding symbioses are: the one that forms fungi with cyanophyceal algae to form lichens and the one that forms the union of fungi with the roots of vascular plants to form mycorrhizae.

Los mycorrhizal fungi, those that establish a symbiotic relationship with plants, are the most relevant for the fruiting of macroscopic mushrooms that we can see with the naked eye and collect. The fungus will act as an extension of the plant's roots, allowing it to have access to water and nutrients that it cannot obtain on its own, thus increasing its chances of survival. The plant will thank the fungus for its help by providing sugars and other substances necessary for its survival.

Also, mycorrhizal fungi connect the roots of some trees to others, allowing them to share resources between individuals.

A forest or ecosystem in which the presence of mycorrhizal fungi is the majority is a healthy forest.

In short, the proportion between fungal life forms serves as a bioindicator of the health of our forest ecosystems and its study could even help us decide whether or not it is appropriate to carry out possible silvicultural action:

• If we find a forest in which the combination of mycorrhizal and saprophytic fungi abounds (in an 80-20% ratio or similar, respectively), we would be talking about a healthy forest.
• If parasitic fungi and saprophytes abound to a greater extent than mycorrhizal fungi in a forest, we would be faced with an ecosystem in decrepitude, which we could help with some silviculture to help the regeneration of the forest.
• The presence of mycorrhizal fungi favors the life of our forests, helping plants to resist, making them stronger in the face of more extreme conditions.
• The presence of saprophytic or decomposing fungi prevents dead organic matter from accumulating and transforms it into nutrients that can be assimilated by plants.
• The presence of parasitic fungi in a plant could cause illness or even death.
• A forest achieves the interconnection of its individuals thanks to the presence of mycorrhizal fungi.
• It is in our best interest to take care of the mycological flora or mycobiota so that the ecosystem does not suffer. Excessive felling of trees or tilling certain areas can destroy mycorrhizae and affect the future of natural areas.

Source: https://www.bbc.com/mundo/media-44704228

José Luis Escobar, Biodiversity