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Do fungal pathogens drive density-dependent mortality in established seedlings of two dominant African rain-forest trees?

Published online by Cambridge University Press:  30 March 2010

Julian M. Norghauer ,
David M. Newbery ,
Leho Tedersoo  and
George B. Chuyong
Julian M. Norghauer*
Affiliation:
Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013, Bern, Switzerland
David M. Newbery
Affiliation:
Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013, Bern, Switzerland
Leho Tedersoo
Affiliation:
Institute of Ecology and Earth Sciences, University of Tartu, 40 Lai Street, 51005 Tartu, Estonia
George B. Chuyong
Affiliation:
Department of Plant and Animal Sciences, University of Buea, P.O. Box 63, Buea, SW Province, Cameroon
*
1Corresponding author. Email: [email protected]
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Abstract:

Where one or a few tree species reach local high abundance, different ecological factors may variously facilitate or hinder their regeneration. Plant pathogens are thought to be one of those possible agents which drive intraspecific density-dependent mortality of tree seedlings in tropical forests. Experimental evidence for this is scarce, however. In an African rain forest at Korup, we manipulated the density of recently established seedlings (~5–8 wk old; low vs. high-density) of two dominant species of contrasting recruitment potential, and altered their exposure to pathogens using a broad-spectrum fungicide. Seedling mortality of the abundantly recruiting subcanopy tree Oubanguia alata was strongly density-dependent after 7 mo, yet fungicide-treated seedlings had slightly higher mortality than controls. By contrast, seedling mortality of the poorly recruiting large canopy-emergent tree Microberlinia bisulcata was unaffected by density or fungicide. Ectomycorrhizal colonization of M. bisulcata was not affected by density or fungicide either. For O. alata, adverse effects of fungicide on its vesicular arbuscular mycorrhizas may have offset any possible benefit of pathogen removal. We tentatively conclude that fungal pathogens are not a likely major cause of density dependence in O. alata, or of early post-establishment mortality in M. bisulcata. They do not explain the latter's currently very low recruitment rate at Korup.

Keywords

central Africadensity-dependencefungicideKorup National ParkMicroberlinia bisulcataOubanguia alataplant pathogensseedling mortalitytropical rain forest
Type
Research Article
Information
Journal of Tropical Ecology , Volume 26 , Issue 3 , May 2010 , pp. 293 - 301
Copyright
Copyright © Cambridge University Press 2010

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