Monday, August 2, 2010: 2:10 PM
411, David L Lawrence Convention Center
Anne Kempel1, Thomas Chrobock1, Markus Fischer1 and Mark van Kleunen2, (1)Institute of Plant Sciences, University of Bern, Bern, Switzerland, (2)Department of Biology, University of Konstanz, Konstanz, Germany
Background/Question/Methods An important question in ecology is which factors determine successful population establishment of plant species. Identification of these factors is particularly relevant for biological invasions (and also for restoration ecology). It has been hypothesized that the ideal invasive plant should possess life-history characteristics such as fast and profuse germination, rapid growth, adaptive phenotypic plasticity and high competitive ability. Empirical evidence for the role of species traits in invasiveness, however, is still scarce. Moreover, the importance of species traits may depend on environmental factors such as soil disturbance and might be overwhelmed by the introduction history of species, including time since introduction and propagule pressure. These factors are often not known for natural invasions, and therefore their importance can only be assessed by controlled introduction experiments. We present results of the first experiment that quantifies and disentangles the roles of species traits, soil disturbance and propagule pressure on establishment success. We experimentally introduced 46 ornamental alien and 45 native herbaceous plant species at different propagule pressures (i.e. numbers of seeds) in eight grassland sites with and eight grassland sites without soil tilling. Of these species, we determine the establishment success over the three years of the project, and assess how this relates to propagule pressure, soil disturbance and species traits. To determine the roles of species traits in establishment success, we assessed seed and germination characteristics, growth rates, induced and constitutive resistances, morphological responses to shading and competitive abilities for most of our study species in greenhouse experiments. Results/Conclusions
Our results from the first two years show that seed mass and proportion of germination in the greenhouse are positively associated with germination in the field, whereas propagule pressure, soil disturbance, growth rate and the ability to produce induced and constitutive resistances against herbivores determine establishment success of seedlings. These results indicate that propagule pressure, soil disturbance and species traits all affect establishment success, but that their relative importance changes over time.
