Vegetation Structure
and DiversityLoss of structure and diversity may lead to:
- Loss of plant species
- Changes in/loss of native ecosystems
- Loss of canopy
- Changes in midcanopy openness
- Changes in views
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There is a negative correlation between abundance of garlic mustard in
the forest understory and the diversity of native plant species
(seedlings in particular), indicating that invasion by garlic mustard
may lead to changes in native ecosystem structure and loss of canopy
forming trees (Stinson et al., 2007; www.nps.gov/plants/alien/pubs/midatlantic/toc.htm).
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In greenhouse experiments, garlic mustard was found to have greater
competitive ability and aggressivity than chestnut oak (Q. prinus),
indicating that the oak forest understory may be more vulnerable to
invasion and that garlic mustard may negatively affect oak regeneration
leading to loss of canopy forming trees (Meekins & McCarthy, 1999).
- Garlic mustard causes changes in soil microbial dynamics, impacting
some mycorrhizal dependent species, leading to loss of native
understory seedlings and herbs, potentially causing loss of canopy
forming trees and native species (Stinson et al., 2006; Burke, 2008; Callaway et al., 2008; Wolfe et al., 2008; www.ipm.msu.edu/garlicAbout.htm).
- Garlic mustard can produce levels of cyanide 150x those of native plants, at levels considered toxic to many vertebrates (Cipollini & Gruner, 2007; Rodgers et al, 2008), potentially leading to changes in native ecosystems.
- Plants grown in soil previously occupied by garlic mustard had reduced germination rate which may lead to loss of native plant species (Rodgers et al., 2008).
- Green rosette leaves of garlic mustard have been found to
significantly increase the decomposition of leaf litter from native
trees, therefore possibly creating a positive feedback between site
occupancy and proliferation (Rodgers et al., 2008), leading to changes in views as garlic mustard becomes the dominant understory plant species.
Insect Diversity-
Garlic mustard is credited with decline of West Virginia white
butterfly due to chemicals that appear to be toxic to butterfly's eggs (www.nps.gov/plants/alien/pubs/midatlantic/toc.htm).
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Relative to eggs laid on native hosts, eggs of the native mustard white
butterfly (P. oleracea) experience reduced survival rate and lower
pupae body weight when laid on garlic mustard (Renwick et al., 2001; Renwick, 2002; Keeler & Chew, 2008).
- In addition, simulated invasion by garlic mustard also reduces both the probability of persistence and mean population size of the native mustard white butterfly (P. oleracea) (Keeler et al., 2006).
Charismatic Bird
Diversity and Abundance
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Garlic mustard may dramatically alter forest structure and composition,
therefore leading to increased predation on songbird nests built in
monospecific stands (Blossey, 1999; Schmidt, 2002).
Historic Landscape - Garlic mustard is suspected to replace sping ephemerals (Cavers et al., 1979; Nuzzo 1993; McCarthy, 1997).