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Fungi and lichens
Fungi and lichens play a very important role in ecosystems and are therefore essential elements of biodiversity in the Brussels-Capital Region. Recently these two groups were included in a regional-scale inventory. The atlas of fungi, which refers to the period 1980-2009, provides an overview of 1,038 basidiomycete species (mainly 'capped mushrooms'), which amounts to almost 60% of all species recorded in Flemish Brabant. In around ten areas in Brussels, including, in particular, the Sonian Forest, there is a significant fungus biodiversity. This study also found that there has been a decrease in symbiotic fungi. In the inventory of lichens, which was drawn up in 2011, 130 epiphytic lichens were recorded. This corresponds to 65% of epiphytic lichen flora in the Flemish Region. Generally speaking, a positive trend could be observed for lichen flora as well. This may be related to a drop in emissions of acidifying pollutants.
Fungi and lichens: essential organisms for ecosystems
Both fungi and lichens fulfil important roles in ecosystems: decomposition of organic material (saprophytic fungi), symbiosis with higher plant species via the fungus roots or mycorrhizas (symbiotic fungi), parasitism (certain fungi), sources of nourishment and shelter for numerous microscopic living organisms (fungi and lichens), colonisation of new environments (lichens), nesting material (lichens), etc. Moreover, fungi and lichens in general are very sensitive to changes in their environment, which makes them good bio-indicators. It is important in this context that lichens are very sensitive to air pollution. The rule is that the more polluted the air, the smaller the variety of species will be. In addition, not all lichen species react in the same way to the different pollutants.
Atlas of fungi
The atlas of fungi of Flemish Brabant and the Brussels-Capital Region was made by the non-profit organisation Natuurpunt with the support of Bruxelles Environnement-Leefmilieu Brussel, among others. The atlas covers the period 1980-2009 and comprises basidiomycetes (mainly capped mushrooms) and myxomycetes (organisms which, although they are no longer considered fungi today, are still being studied by mycologists). Ascomycetes (yeasts, moulds, truffles, morels, etc.) were not included in the inventory.
Based on observations in Brussels 1,038 basidiomycetes could be recorded in the inventory, which is nearly 60% of all species recorded in Flemish Brabant. In addition, 35 myxomycete species and 217 ascomycete species were observed in the Brussels-Capital Region.
In around ten areas in Brussels there is a significant fungus biodiversity. This is especially the case in the Sonian Forest, where a large number of species are found, including rare and threatened species. This diversity can be explained, concretely, by the diversity of soils, biotopes and species present, and by the great extension of the forest area. The historical character of this old forest, the protection it is given, the presence of a large number of old trees and the fairly large volume of dead wood are additional explanations for this richness. Based on the data from before 1980 the authors of the atlas estimate that the number of fungus species recorded here amounts to over 1,000. However, this diversity is distributed unevenly across the Sonian Forest. The richest areas largely correspond to the nature reserves. Fungi are also found mainly on humid and calcareous soils.
As a general rule, the authors of the atlas found that there is a decline in symbiotic species (a generally observed phenomenon in Flemish Brabant and the Netherlands), and in myxomycetes, while there is an increase in saprophytes. Ectomycorrhizal symbiotic fungi (i.e. fungi whose filaments do not enter the plant cells), which are widely present among macromycetes ('large fungi'), are most threatened. This evolution is related to the loss of their natural habitats, the high visitor pressure in certain green spaces (settling of the soil) and signs of eutrophication (insufficient removal of green material and dead leaves, air pollution, nitrogen supply). The apparent decline of myxomycetes, on the other hand, could be ascribed to the fact that they are harder to observe and are only known by a limited number of specialists.
Inventories of epiphytic lichens
Lichens result from a symbiotic association of a fungus and an alga. Epiphytic lichens grow on tree trunks, branches or leaves.
The data below provide an overview of the richness in epiphytic lichens observed in the Brussels-Capital Region during various periods. On the occasion of the 2011 inventory 130 epiphytic lichens were recorded in the Brussels-Capital Region, which corresponds to 65% of all epiphytic lichen flora in the Flemish Region.
These data cannot easily be compared to each other (especially because in the framework of the 2011 inventory nearly twice as many trees were studied than for the previous inventory). However, they leave no doubt that, after a clear period of decline, the trend has been reversed over the past decade.
This positive evolution is related to a reduction in emissions of acidifying pollutants and, in particular, sulphur oxides. The studies performed in the framework of the inventory show which factors, in the environmental conditions that are currently present in the Brussels-Capital Region, have the greatest impact on the species richness and on the type of lichen that is found locally. These factors are: the circumference of the trees and the concentrations of nitrogen oxides and fine particles. In places where these concentrations are high, there is less diversity and growth of lichens.
Measures that benefit the biodiversity of fungi and lichens
The measures of the Region for the conservation of green spaces, the improvement of natural habitats and the reduction of pollution – especially air pollution – have also contributed to the improvement of the fungus and lichen flora.
For fungi, in particular, we can mention the conservation of the diversity of the environments, the recovery of humid areas, the conservation of old trees and dead wood, the fact that dead wild animals are not systematically removed, the restriction of public access to certain areas, the construction of integral nature reserves, the choice of the machines that are used for the works in the forest and the restrictions on the enrichment of the environment with nutrients (e.g. by removing green material and dead leaves from parks). Moreover, since 2002 it has been strictly prohibited to pick mushrooms in the Brussels-Capital Region (with the exceptions of scientific and pedagogical purposes).
Where lichens are concerned, certain more specific management measures can be taken: conservation of wilder areas in the parks, taking into account the attractiveness of the tree species for lichens when planting trees (acid bark for acid-loving lichens, rough bark, etc.), conservation of thick trees, etc.
- STEEMAN R., ASPERGES M., BUELENS G., DE CEUSTER R., DECLERCQ B., KISZKA A., LEYSEN R., MEUWIS T., MONNENS J., ROBIJNS J., VAN DEN WIJNGAERT M., VAN ROY J., VERAGHTERT W. & VERSTRAETEN P. 2011. Paddenstoelen in Vlaams-Brabant en het Brussels Hoofdstedelijk Gewest. 1980-2009. Verspreiding en ecologie, Natuurpunt Studie, study performed thanks to the support of Bruxelles Environnement-Leefmilieu Brussel.
- VAN DEN BROECK D. 2012. Atlas van de epifytische korstmossen en de erop voorkomende lichenicole fungi van het Brussels Hoofdstedelijk Gewest, National Botanic Garden of Belgium, study commissioned by Bruxelles Environnement-Leefmilieu Brussel, 161 pages