PARENT SESSION
Session #21: Current status of knowledge on invasive species: Theory and practice. Organized by: R. C. Anderson and W. R. Perry.
Thursday, August 9, 2001. Madison Ballroom B
Species diversity, resource competition and community invasibility: a Minnesota grassland experiment.
Brown, Cynthia1, Fargione, Joseph1, Tilman, David1, 1
ABSTRACT- We found strong support for the hypothesis that resources left unused by the existing community determine invader success. In particular, greater plant species richness in experimental plant communities led to fewer introduced species, with lower biomass. Seed of 31 introduced species were added to 147 plots with experimentally-established diversities of 1, 2, 4, 8, 12, or 24 plant species. On average, plots with 24 species had 64% fewer introduced species and 85% lower percent cover and biomass of introduced species than monocultures. Higher diversity plots had greater cover of resident species and reduced resource availability, which significantly explained the effects of species richness on introduced species. Performance of introduced species was negatively related to cover of resident species and litter and positively related to resource availability (soil nitrate, soil water, light transmittance, bare ground). Performance of introduced species was not greatly influenced by individual resident species. However, resident species had the greatest negative effect on introduce species from the same functional group, indicating increased competition between species with similar resource use patterns. Our results suggest that greater local species richness can strongly reduce local invasibility through effects of resident species on resource availability.
KEY WORDS: plants, invasion, competition, diversity