Growth in the alpine saxicolous lichens Allantoparmelia alpicola and Melanelia stygia
Hestmark, Geir; Skogesal, Olav; Skullerud, Ø ystein
The growth of the saxicolous lichens Allantoparmelia alpicola and Melanelia stygia was followed in a chronosequence of 240 years of primary colonization in a glacier foreland in the middle alpine zone in the Jotunheimen mountain range and national park in Norway.The largest thallus of A. alpicola was 83 mm in diameter. It was found in the area that had been exposed for at least 240 years. If this individual thallus became established at about the time the habitat was exposed, its average annual diameter increase was 0.35 mm per year. The mean size of the five largest thalli found was considerably lower: 55 mm, an average annual increase of A. alpicola of 0.23 mm. The largest thallus of M. stygia was 120 mm, found in the area that had been exposed for at least 240 years. This gives an average annual increase of 0.50 mm per year. The mean of the five largest thalli was only half the size of the largest thallus: 62 mm. This gives an average annual increase of 0.26 mm. These growth rates are far lower than in most other parmelioid lichens. This is probably due to the short growth season in the high mountains. The growth curve of A. alpicola is close to linear, while M. stygia exhibits a pattern of fast growth in the first years followed by a more or less rapid decrease in growth rate.