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Harvard Forest Symposium Abstract 2005

• Title: Effects of varying environmental and maternal habitats on the performance, demographic structure, and population dynamics of Alliaria petiolata
• Primary Author: Kristina Stinson (University of Massachusetts - Amherst )
• Additional Authors: Cynthia Chang (University of Maryland); Kathleen Donohue (Harvard University)
• Abstract:

  We investigated the sources and mechanisms for population movement and sustainability in the invasive species Alliaria petiolata (garlic mustard) at Harvard Forest. Seeds from open(sun), intermediate, and closed-canopy (forest)source habitats were reciprocally transplanted to each respective habitat in three replicate plots. The number of germinants per pot was counted and plant growth was monitored from April-July, 2004. Analysis of variance demonstrated that both maternal habitat and planting habitat influenced germination rate (p=0.0482 and p<0.0001) and number of leaves produced (p=0.0223 and p<0.001). The source of seeds altered germination success and plant size, such that seeds matured in the forest had higher germination success than immigrant seeds from the sun, but immigrant seeds from sun populations produced more leaves than those from forest populations when grown together in the forest (Figure 1). Seeds originating in intermediate habitats had the highest germination rates in the intermediate planting sites, but did not differ in size from those originating in the other two habitats. A demographic population matrix model was created using census data from nearby sites in each habitat. Overall population growth rate was found be highest in the sun and lowest in the intermediate habitat. In the forest habitat, seeds from the forest population had projected population growth rates less than one, indicating a declining population, whereas seeds from the more sunny locations had projected population growth rates greater than one, indicating population increase (Figure 2). These results indicate that forest populations would decline if only seeds from the forest were available, but that forest populations could be maintained by seeds dispersed from more sunny locations. In addition, the higher population growth rates of populations in sunny locations suggest that these populations are important for the spread of garlic mustard. Populations in sunny habitats contribute to population growth at the forest edge, but because they perform well in other sites they also could be important sources for maintaining forest understory populations as well.
  
  
  

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