POPULATION GROWTH IN CLADONIA STELLARIS (OPIZ.) POUZ. AND VEZDA

Authors


SUMMARY

Populations of Cladonia stellaris in burnt areas of the northern Ontario clay belt were observed photographically from 1968 to 1974. Population growth is logistic with a typical convergent standing crop of 500 g per m2, reached about 30 years after establishment. There is considerable oscillation about the convergent standing crops with time, as well as environmentally determined variations between crops at different sites. Rates of growth are strongly correlated with successional maturity, so that time of establishment may influence the subsequent population size. Final carrying capacity is apparently determined by a complex of factors effective through their influence on light and water availability and by direct physical interference of other species. Ericaceous shrubs and Pleurozium schreberi seem to be the most influential. Cladonia stellaris does not appear until 25 years after fire, but rapidly becomes the most abundant lichen by means of clonal growth. Clones develop by three kinds of budding and subsequently undergo fusion and fission as growth proceeds. Longer range dispersal is by means of small thallus fragments and is evidently highly efficient as newly colonized areas exhibit widespread potential distributions.

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