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Harvard Forest Symposium Abstract 2018

  • Title: Assessing Effectiveness and Community Response to Different Alliaria petiolata Eradication Methods
  • Primary Author: Erin Coates-Connor (University of Massachusetts - Amherst )
  • Additional Authors: Jason Aylward (Harvard Forest); Kristina Stinson (University of Massachusetts - Amherst )
  • Abstract:

    The eradication of the invasive biennial forb Alliaria petiolata (Garlic Mustard) and the restoration of invaded forest habitats present important linked challenges to land managers in North America. Root and leaf litter exudates from A. petiolata contain allelopathic secondary compounds that may interfere with root colonization by mutualistic mycorrhizal fungi for a number of native tree and understory species, thereby impacting growth and recruitment. Removing garlic mustard by hand and by glyphosate herbicide application have both been used as eradication strategies in the Northeastern United States. There are advantages and disadvantages to both eradication methods, such that both methods require many years of applications to deplete A. petiolata’s seed bank. In order to inform effective management practices, there is a need to better understand both garlic mustard population and native plant community responses to these techniques within multi-year and multi-site eradication studies. In this study, we established experimental A. petiolata eradication plots with pulled and sprayed treatments, to compare with invaded and uninvaded control treatments, in four temperate forests in the Northeast. We conducted baseline and annual vegetation surveys each spring for four consecutive years and applied annual eradication treatments following the annual surveys. Our results represent the plant community during and after three consecutive years of eradication treatments. We found a reduction in A. petiolata seedling abundance in all three years following the baseline survey and eradication treatments across sprayed, pulled, and invaded reference plots (p<0.05), with no significant difference in seedling abundance between all three treatments. Adult A. petiolata abundance in pulled plots (N=12) was significantly lower than invaded reference plots (p<0.05) following treatments. Plant diversity indices including species richness and Shannon diversity were lower in uninvaded plots (N=12) than in the other three treatments (p<0.05). Results indicate that manual removal is more effective than herbicide application for reducing adult A. petiolata plants, thereby reducing or preventing new contributions to the seed bank. Furthermore, annual removal of A. petiolata must be continued until the seed bank is exhausted. In terms of community response and recovery, the results indicate that managers should not use increased diversity as a baseline for restoration at these sites. Additionally, disturbance and micro-site variation should be considered as potential drivers of community diversity and composition at these sites.

  • Research Category: Invasive Plants, Pests & Pathogens; Conservation and Management; Biodiversity Studies