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Importance of nurse logs as a substrate for the regeneration of pioneer tree species on Barro Colorado Island, Panama

Published online by Cambridge University Press:  01 July 2009

Evelyn Sanchez
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama
Rachel Gallery
Program in Ecology and Evolutionary Biology, University of Illinois, Urbana IL 61801, USA
James W. Dalling*
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama Program in Ecology and Evolutionary Biology, University of Illinois, Urbana IL 61801, USA Department of Plant Biology, University of Illinois, Urbana, IL 61801, USA
1Corresponding author. Email:


Fallen tree trunks (‘nurse logs’) are important recruitment sites for trees in temperate forest, however nurse log use is seldom reported in tropical forests. We predicted that logs should be important for the regeneration of small-seeded tropical pioneer species because surface leaf litter and competition with established vegetation reduces the establishment success of these species from soil seed banks. In a survey on Barro Colorado Island, Panama, we found that pioneer seedlings were present on logs in 40 of 95 recent treefall gaps. In gaps where seedlings were present on logs, seedling density was not significantly different from adjacent areas of soil. However, species composition was significantly different; logs were disproportionately colonized by smaller-seeded and wind-dispersed species. In growing-house experiments using 12 species, we found that wood substrate had little effect on seed germination. In contrast, seedling growth was 50% lower on decayed wood than soil. Furthermore, species growth rates on wood were not significantly correlated with growth rates in soil (df = 10, r = 0.48). If establishment on logs eventually leads to recruitment to the forest canopy, then logs may promote the maintenance of diversity by favouring a different group of species from those that recruit in soil.

Research Article
Copyright © Cambridge University Press 2009

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