ECOLOGY OF THE CALICIALES

Ecological factors

On the basis of our field knowledge, we have made a list of ecological factors we find significant for the distribution of the Caliciales species in Norway:

• Microclimatic humidity. This is perhaps the most important ecological factor for explaining the distribution of the Caliciales species. The microclimatic humidity is primarily a product of topography and vegetation, not of precipitation.

• Substrate. There are great differences between the species in their ability to grow on various substrates. Some species are very specific regarding substrate, while species with a wider ecological amplitude with regard to substrate, may grow on both organic and inorganic substrates. The most common substrates are lignum, bark, bryophytes and siliceous rock.

• Light. Some species grow on lignum exposed to high light intensity, some may grow in root caves with a very low light intensity, and others may grow intermediate. Several species seem to tolerate low light intensity because of the correlation with high humidity.

• Degree of decomposition of lignum. Whether the lignum is deciduous or coniferous seems to be of less importance. More important is probably the degree of decomposition of the substrate. Slightly decomposed lignum is hard, acid and dry, while well decomposed lignum is softer, more acid and has a higher water capacity tBarkman 1969).

• Dispersal. Most of the species, especially the endosubstratic ones, depend on spore dispersal. The spores are not actively dispersed, but stay in the mazaedium. Short distance dispersal may happen by means of tiny animals like mites. Dispersal of thallus fragments occurs in the sorediose/granular species e.g. Chaenotheca furfuracea, G. stemonea and G. subroscida.

• Continuity of the environment. Perhaps a combination of stable humidity and small temperature amplitude is of importance in climax forests with a high ecological continuity. It is probable that e.g. Chaenotheca subroscida and Cyphelium karelicum demand old spruce forests, while Chaenotheca chysocephala also thrives in younger forests. National parks usually have a high frequency of Caliciales species.

• Pollution or influence of urban areas. Several species avoid urban areas. This may be due to air pollution or other environmental factors produced by towns. Many Caliciales species probably do not tolerate the dryness and the short continuity of the environment in the urban areas. However, according to Barkman (1969), Chaenotheca ferruginea has extended in urban areas in Europe. We have not found this species to be very frequent in the surroundings of Oslo.

• Competition. Bryophytes and lichens (especially Cladonia spp.) are competitors for the Caliciales species. On the Norwegian west coast, with oceanic conditions, bryophytes are abundant on stems and stumps. In the central and eastern parts of Fennoscandia, with more continental conditions, Cladonia spp. overgrow stumps and leave little room for the Caliciales species.