Lichens may be found all over the world, from the Antarctic continent to the tropics, in habitats ranging from spray-washed rocks by the sea, to boulders at the edge of the snowline on mountains; from rain forests to fogy deserts. In harsh, inhospitable environments they may be the only vegetation, and they are amongst the first colonisers of newly exposed rock surfaces, although sometimes algae and bacteria do the same. The only places where lichens might be rare is in or near cities, as they are very sensitive to atmospheric pollution.
These remarkable organisms are not really one plant but two — an association between an alga, or a cyanobacterium, and a fungus; an association so successful that a new entity results, capable of surviving under conditions in which either partner alone would perish.
Lichens are slowly emerging from their obscurity. Considerable work has been done in the last fifty years on the taxonomy of tropical lichens, which opens up the field for ecological and physiological studies.
Last month (May 2011), ITFC had the privilege of hosting Andreas Frisch, a post-doc Lichenologist from the Swedish University of Agricultural Sciences (SLU) in Uppsala. Andreas was in Bwindi to conduct an inventory of the ecology, distribution and diversity of lichens in the park, which is the first such study in Uganda. We managed to interview him about his work.
Here are excerpts from our discussion:
Andreas Frisch observing Lichens in Ruhija, Bwindi INP.
Bwindi Researchers: What is your study about and what is it’s significant?
Andreas Frisch: I’m a lichen taxonomist and ecologist. Together with Lena Gustafsson and Göran Thor (from my department) we are investigating how lichens are distributed in the Bwindi Impenetrable National Park along lines of altitude, disturbance and slope position – meaning whether the epiphytic lichen vegetation of hilltops differs from that of valleys and the slopes inbetween. In the long run we intend to establish lichens in Bwindi as indicator species for forest communities and disturbance levels. We are also working on an inventory of lichens in Bwindi and want to establish a reference collection of lichens at ITFC. We hope in this way we can encourage further research in this fascinating group of organisms.
We feel this study is important as lichens constitute an integral part of the epiphyte communities in Bwindi. These contribute significantly to the microclimate and nutrient supply of the forest and are used by many organisms as fodder, nesting material etc. Lichens are also useful as indicators for environmental conditions, but can only be used as such when the species in the park and their distribution and ecology are well known.
Bwindi Researchers: So far you have spent about 5 weeks traversing several sections of Bwindi. What is your view about the diversity and distribution of lichens in this park?
Andreas Frisch: Bwindi still harbors a high diversity of epiphytic lichens, which might be comparable to that of other African tropical forests of middle altitudes. However, it is difficult to give exact figures as we have just started with our study. During the five weeks in the park I have collected about 250 species along the transects I made and in their surroundings. In total, there might be up to 500 species in Bwindi Impenetrable National Park. This is quite typical for a mid-altitude tropical rainforest in Africa. Low-altitude forests may have a richer diversity of lichens because they are mostly less moist and the epiphyte vegetation is less dominated by bryophytes. Lichens growing on living leaves of trees, shrubs and herbs are particularly common in the lowland rainforests and contribute significantly to the high species richness in these forests. Such foliicolous lichens are also found in Bwindi, but with lower species numbers.
On a single tree trunk, you can easily find 25 plus lichen species. (Photo taken from Bwindi).
Bwindi Researchers: What Is the Ecological Role of Lichens?
Andreas Frisch: Lichens are important partners in nature’s ecosystem. Together with bacteria and algae they are early colonizers that reestablish life on rock and barren disturbed sites. Lichens play an important role in soil formation over much of the earth. As lichens colonize rocks, they trap dust, silt, and water. Soil-crust lichens bind the topsoil and prevent erosion and so play an important role in the ecology of semi-arid and arid lands.
Because of their association with cyanobacteria, some lichens can provide themselves with nitrogen compounds. Lichens contribute to the nitrogen cycle by converting the nitrogen in the air into nitrates that contribute to their growth and development. Their ability to fix atmospheric nitrogen is beneficial to other plant life as well. When it rains, nitrogen is leached from both living and dead lichens and is available to plant life in the immediate areas. When lichens die, they contribute decayed organic matter to the area they inhabited, which enables mosses and seeds from vascular plants to begin developing among the pockets of new soil.
Animals utilize lichens in many inter-dependent ways. It is well documented that numerous animals use lichens for either food or shelter. Some 50 species of birds are known to regularly use lichens as their preferred nesting material. Small animals may use lichens to hide from natural predators through camouflage and direct cover. Mites feed on lichens and some gastropods include lichens in their diet.
In Bwindi, Lichens are quite resilient even to the point of growing on rocks. This one is actually an not a true lichen but an Trentepohlia algae, a common symbiont in lichens, but also as here often free-living
To be continued in next update…