FOLMER Florence¹, HEFFERNAN Colleen², SPIEWAK Mateusz³, 9th International Wildlife Research Week, Riederalp, Switzerland, July 1998 ( © ).

The aim of this project is to study whether there is a relationship between the growth pattern of lichens and the length of period during which the area has been free from the glacier. The research takes place in the surroundings of the Aletsch glacier, near the Riederalp, in the Swiss Alps. Four species of lichens are identified. The diameter of these lichens are measured at six different altitudes. The altitudes correspond to the length of time that an area has been free from the glacier.

The results of the study show that for some species of lichens, the size increases with the time that the area has been free from the glacier, but this is not true for all the species.

It can be concluded that some lichen species follow the predicted pattern of growth, while others do not. There must be other factors influencing the growth of the lichens, and extra research is required to indicate the dominant factors.

In the area surrounding the Aletsch glacier*, there is a large diversity of vegetation. The growth of this vegetation is influenced by the dynamics of the glacier. The aim of this research project is to study the growth rate of lichens in relation to the retreating glacier. Lichens are amongst the first organisms to colonise rocks and bare surfaces. Due to the acids that they secrete and the humus they form, they contribute to early soil formation.

A lichen is a union between a green alga and a fungus. The fungus gains oxygen and carbohydrates from the photosynthetic activities of the alga, whilst the alga obtains water and mineral salts from the fungus. The fungus also provides protection against being washed away and from drying out in warm weather. This partnership is called a symbiosis.

To carry out the investigation, seven sites of varying altitudes were chosen. The altitudes were measured using an altimeter. The chosen altitudes correspond to the amount of years that an area has been free from the glacier (see appendix 1). At each of these sites, the following methodology was implemented:

1) Once the correct altitude had been reached, an area devoid of shade and which had numerous rocks was chosen.

2) Four species of saxicolous lichens were chosen at each site as follows:

Stereocaulon alpinum, Rhizocarpon geographicum, Lecanora conizaeoides and Umbliricaria spadochroa.

3) The lichen size was then measured using a Vernier Callipers. The widest part of the lichen was measured for each species, and its area was calculated.

4) Details of the environment were noted.

5) The data was plotted as graphs.

Table 1 shows the measurements of the lichens’ area at each altitude. The second column gives the relation between the altitude and the amount of years that the selected site has been free from glacier.

Figure 1 illustrates the relation between the amount of years that the selected site has been free from the glacier and the size of Stereocaulon alpinum lichens.

Figure 2 illustrates the relation between the amount of years that the selected site has been free from the glacier and the size of Lecanora conizaeoides and Umbliricaria spadochroa lichens.

Figure 3 illustrates the relation between the amount of years that the selected site has been free from glacier and the size Rhizocarpon geographicum lichens.

The results indicate that the size of Stereocaulon alpinum increases up to a certain maximum, and then, the species is no longer found at the selected sites (see figure 1). The size of Umbliricaria spadochroa and Lecanora. conizaeoides increases up to a certain maximum the further the lichens grow from the glacier, and then it gradually decreases (see figure 2). Only the species Rhizocarpon geographicum shows a consistent area increase with its distance from the moraine of the glacier (see figure 3). This variation of growth pattern between the species (see table 1) suggests that there are other factors influencing the growth of lichens. If their growth depended only on the rate of glacier retreat, then all recorded patterns should be similar.

Other influencing factors may be the altitude, the soil temperature, the degree of exposure to sun and rain, the consistency of the substrate, parasites, and foraging mites and slugs. A more detailed study over a longer period of time would be required to explain completely the growth pattern of these lichens. A comparison study at a similar altitude would also help in explaining why, in the area of our study, some species no longer grow at certain altitudes. The two species Stereocaulon alpinum and Lecanora conizaeoides reached maximum growth at the altitude of 1900 m (site that has been free from glacier for 90 years) (see figure 1 and 2). It would be interesting to determine if they followed the same pattern at a similar location in another habitat.

For Rhizocarpon geographicum, the growth displays a very good correlation with altitude, and the graph of figure 3 can be used to evaluate the size of this lichen at any particular altitude at this location.

We are very grateful to the following people and institutions:

Jahns. H.M. 1980. Farne-Moose-Flechten. BLV Bestimmungsbuch. München.

Richard J.L.1973. Dynamique de la végétation au bord du glacier d’Aletsch (Alpes Suisses). Ben. Schweiz. Bot. Ges. 1973:3 (Volume 3).

map: Aletschgletscher Landeskarte der Schweiz 1:25000, Bundesamt für Landestopographie, 1993.