Bruce introduced us to this fascinating topic by pointing out that fungi have a close association with vegetation performing a variety of important roles. The management of vegetation should always include consideration of fungi. Unfortunately there is a general lack of awareness of the significance of fungi in ecosystems in the UK especially when compared to continental countries. The link between fungi and vegetation is also important for field mycologists since we can learn where to go to look for specific fungi. For example, Marasmius buxi is only found on box leaves and we are wasting our time looking for it anywhere else. Bruce went on to consider the relationship fungi have with different types of vegetation.
Woodlands
As decomposers probably the major role of fungi is linked to the substrates cellulose and lignin where they are involved in recycling these compounds back into the environment. Fungi have a central role in the recycling of wood and leaf litter whereas bacteria only have a marginal role. Some species are very selective as to the substrates that they will grow on e.g. some Gymnopilus species such as G. penetrans only grow on conifer wood.
Many fungi including some of the larger agarics and the truffles form ectomycorrhizal associations with trees. Birch and conifers often grow together and some mycorrhizal fungi can switch between them. Amanita muscaria can be found over much of Europe in birch plantations whereas in North America it is usually found with pine. In contrast, Amanita phalloides is associated primarily with either oak or beech and is commonly found in oak and beech mixed woodland. If the fungus is not host specific it may form a link with different species of trees enabling the transfer of nutrients between them. Using radioisotopes it has been demonstrated that carbon is transferred between individual trees via their fungal partner and there is a net transfer of carbon to stressed trees - a wonderful example of altruistic behaviour. On the other hand some non-green orchids have evolved to be parasitic on mycorrhizal fungi growing with trees.
Not all trees have ectomycorrhizal associations with fungi. Ash and sycamore form endomycorrhizal associations with much smaller and primitive fungi that do not form visible fruit bodies on the ground. These associations are also much less specific. Sycamore is not native to Britain and has only really become established over the last 200 years finding a niche in our largely deforested country where it can easily spread.
Some fungi are parasitic on trees but even these may have a role to play in thinning forests. However, many problems with parasitic fungi are a byproduct of forest management due to careless felling or from heavy machinery being driven through forests that can damage the underground mycelium of beneficial mycorrhizal fungi and cause wounds on trees that become infected. Mycorrhizal fungi take much longer to recover from damage to their mycelium than saprophytic fungi and it is not always obvious when the damage has occurred. For example, damage caused by acid rain may have occurred decades earlier.
Grasslands
Waxcaps (Hygrocybe spp.) are generally found on unimproved grasslands in the UK although in North America they are considered to be a woodland species. Bruce believed this may be related to similarities in summer soil temperatures between grasslands in the UK and the woodlands of North America. When our forests were cleared this would have expanded the habitat of these fungi. Fruiting only occurs where the grass is short either through grazing or where it is regularly mown. The ratio between carbon and nitrogen in waxcaps and also earth tongues (Geoglossaceae) and fairy clubs (Clavariaceae) all of which are found on nutrient-poor grasslands is very different to other fungi. As such they represent a distinct ecological grouping. Waxcap grasslands have come to the fore in recent years due to their conservation status.
Heaths
There are relatively few species of fungi that can survive with heather since exudates from its roots inhibit most of the mycorrhizal fungi associated with trees. Thus heather has evolved an effective mechanism for preventing trees from competing with it by specifically inhibiting their associated fungal partners.
Costal Habitats
Costal areas where a series of sand dunes have formed can be rich in fungi as typified by Ainsdale one of our best sites for fungus forays. At Ainsdale the different stages of a succession of a dune system from yellow dunes to conifer plantations can be seen.
Yellow Dunes
Yellow dunes are the dunes nearest the sea. At this stage marram grass can stabilize the sand because of its deep vertical and extensive horizontal root system. The clumps of marram grass are continually buried but can re-grow through the newly deposited sand. Specific fungi to be found in this habitat growing on the dead remains of the grass include the Dune Brittlestem (Psathyrella ammophila), the Dune Cup (Peziza ammophila) and the Sand Stinkhorn (Phallus hadriani).
Grey Dunes
With increasing distance from the beach the conditions for plant growth improves giving rise to fixed and more stable dunes. Grey dunes are characterized by the presence of grasses, lichens and moss. The dunes may also be colonized by Creeping Willow (Salix repens) a low-growing bush that can support opportunistic ectomycorrhizal fungi usually associated with trees including a range of Cortinarius species and many other genera.
Dune Slacks
The hollows between the dunes are known as ‘slacks’ and are often wet for much of the year. Dune slacks are home to many wild-flowers and also Creeping Willow with its associated fungi, although a different suite of species are to be found here.
Dune Heath
The build-up of humus eventually gives rise to a sandy soil capable of supporting pasture grasses that are often grazed short by rabbits. Species of fungi found in dune heath include the Winter Stalkball (Tulostoma brumale) and the Scaly Stalkball (Tulostoma melanocyclum).
Forest behind the Dunes
The area behind the dunes is typically planted with conifers in an attempt to stabilize the sandy soil. At Ainsdale the remains of commercial Corsican pine plantations have since taken on a more natural aspect. These forests are good places to find characteristic pinewood species of fungi and in addition a variety of Geastrum species or Earthstars are frequently found. It is not known if the latter are mycorrhizal or are simply leaf litter decomposers.
Shingle Beaches
Only some of the larger beaches in the UK are able to support vegetation and there are few fungi to be found in this habitat, mainly plant pathogens, some puffballs and myxomycetes.
Mountain Habitats
Specific mycorrhizal fungi can be found on fell tops having an association with Least Willow (Salix herbacea) which forms very low prostrate mats. They include Amanita muscaria (Fly Agaric), Amanita nivalis which is restricted to this habitat and Boletus edulis (Cep or Penny Bun). Many of these species are normally ectomycorrhizal with forest trees. Where there are limestone outcrops other associations may be found for example Boletus luridus and Mountain Avens (Dryas octopetala). Common Rockrose (Helianthemum nummularium) can support a range of fungi including boletes and Amanita muscaria.
Bruce also mentioned the so called snow-line myxomycetes that only fruit in close association with snow or under snow cover and as such are now threatened by climate change.
Wetlands
Species of fungi found in acidic sphagnum bogs include Galerina, Hypholoma and a few ascomycetes. Fens fed by alkaline, mineral-rich groundwater (base-rich) can have a very rich assemblage of uncommon fungi that includes the rare Armillaria ectypa so unlike any other Armillaria species in its choice of habitat. Mires having a slightly acidic to neutral pH include reed swamps which can support a wide range of hyphomycetes and ascomycetes growing on the herbaceous debris.
Aquatic Habitats
In streams where there are twigs and branches freshwater ascomycetes may be found growing on the wood underwater. Professor C. T. Ingold was the first mycologist to recognize the freshwater ascomycetes as a distinctive group and also discovered the aquatic hyphomycetes, asexual fungi adapted to aquatic habitats (now known as Ingoldian hyphomycetes).
Bruce completed his presentation by emphasizing the importance of including the fungal components of different biotopes in inventories of sites for ecological, conservation protection and site management objectives. As fungi are such essential components of so many different habitats we cannot afford to overlook their importance when conserving sites. Fungi are an indispensable part of the ecosystem and should not be ignored.
