Growth, population density and population structure of Cetraria nivalis during 240 years of primary colonization

Abstract

The growth of the alpine lichen Cetraria nivalis was followed in a chronosequence of 240 years of primary colonization in a glacier foreland in the Jotunheimen mountain range and National Park in Norway. The largest thallus of C. nivalis was 96 mm in diameter. It was found in the area that had been exposed for a maximum of 240 years. If this individual thallus became established at about the time the habitat was exposed, its average annual diameter increase has been 0·4 mm per year. The growth curve of C. nivalis does however exhibit a pattern of fast growth in the first years followed by a decrease in growth rate. In contrast the population density of C. nivalis increases through time in a linear manner, from 0·4 thalli/m² in the areas recently exposed to 10·5 thalli/m² in the sites exposed for maximum of 240 years. This suggests a fairly stable flow of propagules over the landscape through the years. The size distribution (population structure) of thalli within the foreland is skewed, with many small individuals and few big ones.