Seed limitation and the regulation of community structure in oak savanna grassland

Authors

  • Bryan L. Foster,

    Corresponding author
    1. Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA, and
      Bryan L. Foster (tel. 785 864 4361; fax 785 864 5360; e-mail bfoster@ku.edu).
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  • David Tilman

    1. Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA, and
    2. Department of Ecology, Evolution & Behaviour, 1987 Upper Buford Circle, University of Minnesota, St Paul, MN 55108, USA
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Bryan L. Foster (tel. 785 864 4361; fax 785 864 5360; e-mail bfoster@ku.edu).

Summary

  • 1We present results from a long-term sowing experiment conducted in nutrient-poor savanna grassland in eastern Minnesota. We examine the effects of a one-time seed addition of 23 grassland species on plant community dynamics and structure over eight growing seasons.
  • 2Our goals were to: (i) test the importance of seed availability in regulating plant colonization dynamics and species richness; (ii) assess both the initial effects of sowing on species diversity and community structure and whether these effects increased, persisted or dissipated over the long-term; and (iii) determine the long-term impacts of sown species on the structure and dynamics of the existing community, including effects on species diversity, the abundance of existing (non-sown) species, extinction rate and abundance hierarchy.
  • 3Sowing led to the successful establishment of several plant species that had not been present in the plots and to increased abundance of other species that were already present.
  • 4Sowing led to sustained, significant changes in community structure, including increased species richness, increased community evenness, and decreased absolute and relative abundance of non-sown species. Effects of sowing were large and significant 8 years after sowing, revealing the role of seed limitation in these grassland communities.
  • 5In total, the results suggest that dispersal limitations, species pools and local biotic processes interact to regulate plant community structure.

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