Litter fall of epiphytic macrolichens in two old <i>Picea abies</i> forests in Sweden

Abstract

The seasonal and annual variation in the litter fall of epiphytic lichens and tree litter was studied over a period of 2 to 3 years at two forested hills in the eastern part of central Sweden. Litter fall was measured using traps and for one species, Usnea longissima, by collecting specimens present on the ground. Total litter fall amounted to 2.5 and 2.8 tons ha −1 year −1 of which lichens constituted 4.6 and 5.7% at the two sites. Lichen litter fall was highest during the period from late autumn to the beginning of summer. Both the lichens and the tree litter showed significant between-year differences. Usnea longissima had an annual turnover of 7.0 and 10.0% of the standing crop at the two sites. The thallus length distribution of U. longissima was positively skewed. It is concluded that dispersal of thallus fragments by wind evidently plays an important role for many of the filamentous lichens studied. It is suggested that U. longissima disperses over a much shorter distance than Alectoria sarmentosa and Bryoria spp. within a forest stand.