Colonization of old-forest lichens in a young and an old boreal Picea abies forest: an experimental approach

Understanding the factors limiting the distribution of a species is crucial for designing conservation strategies. We evaluated whether the scarcity o f old-forest lichens in young forests was due to unfavourable environmental conditions for colonization in young stands or to dispersal limitations. V egetative diaspores of Lobaria scrobiculata, Platismatia glauca and Platism atia norvegica were sown on 240 spruce twigs transplanted to a young and an old stand of spruce. Our results demonstrate that the old-forest species e stablished and grew as rapidly in the young as in the old forest. Higher li ght levels in the young, compared with the old forest, did not reduce diasp ore development. Moreover, greater numbers of juvenile thalli of Platismati a were found on control twigs (unsown) in the old forest, compared with the young forest, suggesting higher propagule density and more efficient dispe rsal in the old stand. Our results indicate that life-history characteristi cs, which include dispersal characters, are important for explaining the sp ecies scarcity in younger stands. Minimizing the distance between regenerat ion units and potential sources of propagules is probably important for mai ntaining lichen biodiversity in managed forest ecosystems. (C) 2001 Elsevie r Science Ltd. All rights reserved.