The life of the forest. Fungi

A forest is a place where thousands of different organisms meet, creating the most complex network of connections that can exist in nature. Forest ecosystems are also huge factories where solar energy and carbon dioxide from the atmosphere are turned into a huge amount of biomass, which makes up ecosystems but is also constantly changing. A forest is a system in which each organism plays a role and has an assigned function. It is worth considering the importance of fungi for the functioning of the forest, the most mysterious group of organisms in this forest puzzle. Life of the Forest – Fungi Fungi, that is, representatives of one of the five kingdoms of the world of living organisms, play an extremely important, often unnoticeable or underestimated role in the functioning of all ecosystems, including forest ecosystems. It is also one of the richest groups of organisms in terms of species all around the globe. It is estimated that there may be even over 5 million species of fungi on our planet. A walk in the woods, especially in the fall, can be an opportunity to get to know the amazing variety of fruiting bodies that fungi produce. Our attention is especially drawn to the so-called larger fungi, otherwise known as macrofungi. Their fruiting bodies can be seen with the naked eye. Mushrooms are undoubtedly the most famous fungi. Their fruiting bodies vary greatly in size and colour. The size of some of them does not exceed one centimetre, but we can also find those with caps that extend over 20 centimetres. It is also worth paying attention to the huge variety of fruiting body colours, which depends on the species. On our path, we can come across mushrooms with caps ranging from white through yellow, green, olive, pink, red, brown and to dark brown. However, mushrooms are not the only fungi found in the forest. An attentive observer will also find fungi with different fruiting bodies, often surprising in form, which can be cup-shaped, bush, spherical, bulbous, pear-shaped, star-shaped or funnel-shaped. Most fungi, colloquially known as bracket fungi, produce fruiting bodies resembling tongues, consoles or hooves. The fruiting bodies are made with basically one purpose, to produce huge amounts of spores, which is one of the primary ways for fungi to spread. When observing fruiting bodies, it is also worth paying attention to the variety of forms of the hymeniform, that is, the layer in which spores are produced. The species that predominate among the fungi have tubular or lamellar hymeniform. However, we can also meet species with a more unusual hymeniform, that is spiny, labyrinthine or smooth. Contrary to appearances, fungi form fruiting bodies almost all year round. For example, velvet shanks appear in September and are found until April, usually in frost-free periods. Fruiting bodies of velvet shanks usually grow near stumps of deciduous trees. They are saprophytes and therefore decompose dead organic matter. A similar method of obtaining carbon compounds can be observed in many fungi. In early spring, fruiting bodies of common morals appear, fungi that are currently under partial protection, or of equally rare false morals. In the summer season, we can often find fruiting bodies with unusual colour. Caps of Verdigris agaric are turquoise in colour and they often sprout up from rotting logs, usually in older forests. Their shimmering caps are a real decoration of the surroundings. As a rule, saprotrophic fungi have their own food preferences. A significant part of them is related to dead wood. The fruiting bodies, commonly called bracket fungi, are observed in every forest. Many arboreal fungi are particularly rare and protected species. Due to their presence, arboreal fungi gradually break down the wood. Ecological niches useful for other species appear over time. Due to this specific succession, huge trees often get a second life after their death, during which hard and compact matter turns into dust in a long time process. Whether fungi break down organic matter from the soil or live on dead wood, they play a key role in the circulation of elements and energy in nature. The efficiency of fungal decomposition is best seen when observing the decomposition of forest litter, in which, among many organisms, fungi, both larger and microscopic ones, play a leading role. Another way for fungi to gain nutrients is to live at the expense of other organisms. The pathogenic fungi in question attack many organisms, including plants. In natural forests, pathogenic organisms are a natural component of ecosystems in which they play an important role and are regulators of other organisms. This is not the case for forests that have been heavily influenced by humans over the last decades. The maladjustment of the species composition to the habitat and the simplification of the spatial and age structure make such forests particularly sensitive to the presence of fungal pathogens. An example is the massive dieback of oaks. The process that affects these majestic trees since the 1980s is caused by fungus-like oomycetes, leading to the so-called fight of thora. In the first stage of the oak dieback, the infection of the roots begins, followed by further damage to the trees, related to the attack of insects feeding in the crowns and wood. The spiral of death into which single trees are woven causes changes in the entire forest ecosystem, which are most visible in changes in the species compositions of undergrowth plants. Currently, next to oaks, the most endangered trees are ash trees, attacked by the fungus Haemescipus fraxinea, discovered at the beginning of the 21st century. This pathogen creates small fruiting bodies on ash shoots. While old trees resist the attack, it basically completely eliminates young ash trees that are regenerating themselves. Elms are another threatened tree. The first reports of a massive dieback of elms appeared at the beginning of the 20th century. During this time, 10-40% of all elms growing in Europe and North America were affected. Later, a new species of fungus was described, Ophiostoma nova ulmi, which caused an almost complete extinction of the mountain elm in southern England in several years. Small insects, large elm bark beetles, which are the only vector that transfers the fungus to new areas, contribute to the spread of Ophiostoma fungi. Mycorrhizal fungi are an extremely interesting group of fungi, without which it is difficult to imagine the functioning of terrestrial ecosystems, including forests in their present form. Throughout their life, they remain in a close symbiotic relationship with plant roots, creating mycorrhizae. Mycorrhizae is not a homogenous phenomenon or system. Its division into different types is most often related to the systematic position of the plant partner. Heather plants, represented in forests, for instance by blueberries and heathers, form the so-called erichoid mycorrhizae. A separate type of mycorrhizae is also created by orchids whose flowers please our eyes during forest walks. The most common type of mycorrhizae in terrestrial ecosystems is the abuscular mycorrhizae. It occurs in most herbaceous plants, including forest ones. Also, some shrubs, such as buckthorn, bird cherry, as well as some forest trees, such as maple and ash, are characterized by the presence of arbuscular mycorrhizae. However, the most important type of mycorrhizae in the forests of our climate zone is ectomycorrhizae. It applies to most of our forest trees, such as pines, spruces, larches, oaks, beeches, lindens, birches, and hornbeams. When in contact with the mycelium of the ectomycorrhizal fungi, the fine roots of these trees lose their hairs, fundamentally change their morphology, undergo numerous branches, and their surface is covered with fungal hyphae. The mycelium forms the so-called mycelial muff, the structure and color of which depend on the fungus species. Thanks to this, this underground world of ectomycorrhizae does not differ in diversity from the variety of fruiting bodies. Most edible species are found among the fungi that form ectomycorrhizae with forest trees. These include large boletes, baeboletes, boletus, chanterelle, edible milk caps, or russules. Inedible and poisonous fungi, which are ectomycorrhizal, include, for instance, toadstools. Mycorrhizal fungi, unlike saprotrophic fungi, have lost the ability to decompose and use dead organic matter as a carbon source. In this respect, they depend entirely on their plant partner to donate to them some of the carbohydrates produced in photosynthesis. In return, fungi, thanks to the extensive mycelial network extending over the substrate, provide plants with increased access to water and minerals. Additionally, they are an element of protection of the plant partner against soil pathogens. The ectomycorrhizal fungal hyphae spreading over considerable distances in the soil form the so-called common mycorrhizal network. It connects the roots of trees, even those belonging to different species, so that one common superorganism is created. The purpose of this network is also to support the growth of seedlings under the canopy of adult trees. Autumn is the time when we especially like going to the forest. Most often, it is not only due to our willingness to commune with nature. The aim of these trips is mushroom picking, which can be safely called a national sport of Poles. Mushroom picking has a centuries-old tradition in our culture. Undoubtedly, many of us remember the very pictorial description of mushroom picking, which was included in the third book of Pantadeusz by Adam Mickiewicz, Poland's national bard. In September and October, when the weather is favorable for fungi, forest parking lots and roadsides fill up. In many regions of Poland, you can then meet dozens or even hundreds of people setting out on mushroom hunting. Most often, they collect some of the most known species, such as large boletes, bay boletes, boletus and birch boletes. Most of the collected mushrooms are intended for personal use. Some mushroom pickers, however, treat autumn trips to the forest as a source of additional income. We can buy fresh mushrooms on the sides of roads running through forests, at city markets and more and more often in large supermarkets. The trade also includes dried mushrooms in various pickles or constituting an ingredient of various dishes, for instance dumplings or patties. Polish law allows for the marketing and processing of 44 species of fungi, most of which are forest mushrooms. Despite media reports of poisoning, unfortunately often fatal, caused by the consumption of poisonous fungus, such cases are repeated every year. One of the most dangerous mushroom killers is undoubtedly the Amanita phalloides, commonly known as the death cap. It is most often confused with the edible russule, yellow knight or parasol mushroom. In today's changing world, the priority is the protection of nature and the protection of biodiversity. The best way to protect fungi is to take special care of their natural habitats. Since we find the greatest species richness of fungi in forests, therefore, by protecting the most valuable forests, we also protect the world of fungi occurring in them. It is often a world of incredibly rare and endangered species. This is the case, for example, in the forests of the Białowieża primeval forest, which is the best studied forest complex in Poland in terms of the fungi found there. The dizzying amount of micro-habitats associated with a huge amount of dead wood of varying degrees of decomposition, but also the diversity of these habitats, makes it an ideal place for fungi conservation. However, the vast majority of forests in Poland are managed forests. In such forests, fungi can be used as indicator organisms, useful for observing the impact of changes in forest ecosystems due to human activity. The managed forest is a place where various, often contradictory expectations and goals meet. In addition to protective functions, the forest also performs economic functions related to the production of wood. The biggest paradox with wood, the most natural, renewable and fully biodegradable raw material, is that perennial trees must be cut down to produce it. On the one hand, wood is a raw material without which it is difficult to imagine our lives. On the other hand, the sight of trees being cut down and felled often causes indignation and anger. However, the life of the forest goes on. In order to reduce the negative effects of human interference, it is important to ensure the fastest possible regeneration of the ecosystem, preferably with the use of natural processes. The best example of this is the promotion of natural regeneration, thanks to which the forest regenerates very quickly. Leaving the felling remnants also allows you to find ecological niches suitable for various fungi. The spread fruiting bodies of the Tomenthala genus are a great peculiarity of deciduous forests. The appearance of fungi in the forest, first the common ones, with time other rarer ones, proves how quickly the forest is able to heal wounds. In this way, the young generation of the forest takes care of its fungi, and they support the newly created forest. The use of natural processes is not always possible to the same extent. Poor pine forests are a common landscape feature in many parts of the country. Contrary to appearances, such forests are quite rich in fungi found in them. From porcinos, chanterelles, or babeletes, to less known russules, milkcaps and webcaps. To ensure the persistence of fungi, it is necessary to restore the forest as quickly as possible. It is very important to introduce other tree species wherever possible. Each newly introduced tree species, which will diversify the species composition of the forest, will in the future create a niche for the occurrence of hundreds of fungal species associated with it. Most of the planting material used in artificial forest regeneration is produced in field nurseries. All our forest trees are, obligatorily, mycorrhizal species, which means that they are not able to grow properly without being associated with mycorrhizal fungi. Hence, it is extremely important that tree seedlings produced in nurseries are characterized not only by the correct growth parameters, but also by a high degree of colonization by mycorrhizal fungi, diversified in terms of species. This is an element that undoubtedly influences the high efficiency of planting and afforestation. Many years of research conducted at the Institute of Dendrology of the Polish Academy of Sciences in Kurnik have proven that, in this respect, the Polish forest nursery can be a model to follow. The world today brings many dangers to the diversity of the fungi world. One of them is the over-exploitation of forest resources. For example, a shift away from the model of sustainable forest management to plantation crops. Improper actions in managed forests can permanently change the nature of forests by simplifying their structure and species composition, which will also have a negative impact on the world of fungi. The serious consequences of errors in forest management can be observed today in many single species stands established at the beginning of the 20th century. The maladjustment of the use of seeds from unknown origins and the focus on rapid growth make such forests more vulnerable to threats. The change in climate, more frequent and longer droughts and frost-free winters, result in massive outbreaks of xylophagous insects and fungal pathogens. The change in climate means also more and more frequent extreme weather phenomena, such as storms, tornadoes and heavy rains. The cascade of events triggered at the moment of the forest death also affects the world of fungi. Mass forest dieback is the greatest threat to the diversity of fungi, especially the symbiotic fungi associated with living trees. This is a loss of habitat for thousands of species of fungi associated with forests. That is why the fight for the sustainability of the forest is so important. For each piece of the forest that resisted the unfavorable currently observed changes. Among our native fungi, there are more and more newcomers from far away. Foreign species often make impression with their colors and shapes. Octopus stinkhorn occurs naturally in Australia and New Zealand. It came to Europe at the beginning of the 20th century, probably along with imported goods. In recent years, it has become quite common in Poland. The octopus stinkhorn spores are spread by flies attracted by the smell of perishable meat. Another newcomer from distant lands is a mat jack. It came to Europe from North America along with Douglas fir. This duo has also been dragged to other parts of the world. In the southern hemisphere, especially in South America and New Zealand, a mat jack is a decisive factor in the invasiveness of Douglas fir, which is a great threat to native tree species. From North America, we have also received an Aureoboletus projectolus. For several years, it has been more and more often found in the dry pine forests of the coastal belt. This mushroom in Poland is known as a heather boletus. Its characteristic feature is a grooved stem, not found in our native mushrooms. Aureoboletus projectolus has been harvested by mushroom pickers for several years. At the end of August and September, they appear en masse, creating thousands of fruiting bodies. And this attracts mushroom picking enthusiasts from many parts of Poland. Heather boletus has become a tourist attraction of coastal forests. However, it should be remembered that this is a species of foreign origin, the impact of which on our native ecosystems and species of fungi has not yet been understood. Mass collections of Aureoboletus projectolus meant that it was moved to the interior of the country. The vector that contributes most to the spread of this fungus to new areas is man. When wandering through forests, we should remember that a forest is not only trees, bushes and undergrowth plants. It is a very complex system in which different groups of organisms coexist. Among them, fungi play an important role. Remember that the fruiting bodies of fungi are an important element of a number of food chains. They are food for many rodents, snails or insects. Therefore, mindless destroying of the fruiting bodies should be avoided. The fact that they are not culinarily attractive to us does not mean that they are redundant. Through a number of different functions, fungi ensure the sustainability and proper functioning of the forest ecosystem. It is hard to imagine the sudden disappearance of the fungi and the consequences it would have.