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Mortality in seedling populations of Silver Birch: genotypic variation and herbivore effects

  1. K. Prittinen1,*,
  2. J. Pusenius1,
  3. K. Koivunoro1,
  4. M. Rousi2,
  5. H. Roininen1,†

Article first published online: 29 SEP 2003

DOI: 10.1046/j.1365-2435.2003.00777.x

Issue

Functional Ecology

Functional Ecology

Volume 17, Issue 5, pages 658–663, October 2003

Additional Information

How to Cite

Prittinen, K., Pusenius, J., Koivunoro, K., Rousi, M. and Roininen, H. (2003), Mortality in seedling populations of Silver Birch: genotypic variation and herbivore effects. Functional Ecology, 17: 658–663. doi: 10.1046/j.1365-2435.2003.00777.x

Author Information

  1. 1

    Department of Biology, University of Joensuu, PO Box 111, FIN-80101 Joensuu, and

  2. 2

    Punkaharju Research Station, Finnish Forest Research Institute, FIN-58450 Punkaharju, Finland

  1. †

    Present address: Vantaa Research Center, Finnish Forest Research Institute, PO Box 18, FIN-01301 Vantaa, Finland.

* †Author to whom correspondence should be addressed. E-mail: Kaarina.Prittinen@joensuu.fi

Publication History

  1. Issue published online: 29 SEP 2003
  2. Article first published online: 29 SEP 2003
  3. Received 28 January 2003;revised 5 May 2003;accepted 26 May 2003

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Keywords:

  • intraspecific competition;
  • multiple herbivory;
  • population structure;
  • resistance;
  • self-thinning

Summary

  • 1
    Variation among mature plants reflects mortality that has occurred during the seedling phase. Our earlier studies have shown variation in resistance to insect and vole herbivory among Silver Birch genotypes that represent variation in a naturally regenerated birch stand. The aim of this study was to examine whether seedling mortality varied among these genotypes, and whether insect and field vole herbivory affected mortality. The 20 genotypes studied competed with each other in dense stands, which were randomly assigned to insect and vole exposure and fertilization treatments.
  • 2
    Insect herbivory and fertilization increased mortality significantly (by 98 and 68%, respectively). The fertilization effect was probably due to accelerated self-thinning among fast-growing seedlings. Although vole browsing removed considerable biomass, it did not affect seedling mortality.
  • 3
    Mortality was context-dependent. The genotypes differed both in their overall mortality and in their response to insect herbivory. However, the effect of insects on a genotype depended more on its success in competition than on its resistance: even small amounts of feeding were detrimental to short, shaded seedlings, while taller seedlings in the canopy were affected less, although they were eaten more.
  • 4
    It is concluded that moderate levels of insect herbivory can increase seedling mortality considerably. Furthermore, herbivory can change the genetic structure of birch populations through selective mortality, which in dense stands is dependent on competitive traits.
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