Vegetation Structure
and Diversity
Loss 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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In a long-term study of successional dynamics, cover of red maple (A.
rubrum) and eastern redcedar (J. virginiana) were found to be inversely
related to changes in multiflora rose cover, indicating the species had
an inhibitory effect on the growth of on one another (Banasiak & Meiners, 2009). Over time this may lead to changes in ecosystem structure as dominant tree species are lost.
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Multiflora rose can grow as a vine or shrub, giving it the ability to
both cover canopy trees or create new canopy, therefore changing or
eliminating most or all layers of vegetation below (www.natureserve.org - Swearingen, pers. comm., 2001).
- Mulitflora rose may form monocultures and displace native species in open woodlands, forest edges, prairies, and savannas (www.natureserve.org - Swearingen, pers. comm., 2001).
- Multiflora rose can provide greater cover for foraging seed
predators, therefore leading to greater seed discovery and removal (Meiners & LoGuidice, 2003; Meiners, 2007), potentially leading to changes in canopy forming tree density, community structure, or species composition.
- During a study of the invasion dynamics of both invasive and native
plant species in abandoned agricultural fields, four invasive shrub
species, including multiflora rose, were associated with declines in
species richness (all plant species present in sampling plots) while
invasion by natives did not cause changes in species richness (Meiners et al., 2001).
- Amur honeysuckle (L. maackii) residence time has been negatively
associated with the density of tree seedlings though reduced light
levels and resource competition. Allelopathic toxins produced by this
species reduce native plant growth (Collier et al., 2002), potentially leading to loss of canopy forming trees.
- Japanese barberry (B. thunbergi) forms dense stands that suppress growth co-occurring herbaceous species (Silander & Klepeis, 1999), potentially leading to loss of natives.
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Common buckthorn (R. cathartica) can comprise up to 50% of understory
plants and the resulting leaf litter causes bare soil conditions
beneath stands leading to loss of biomass and changes in ecosystem
structure (Knight et al, 2007).
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Barberry (B. thunbergi) can both change soil characteristics and form
dense monocultures, making it hard for native understory plants to
re-establish (www.natureserve.org, www.nps.gov/plants/alien/pubs/midatlantic/toc.htm) leading to a change in community structure or loss of species.
Insect Diversity- Pitfall analysis has shown that multiflora rose shrubs support fewer insect species (Clifford & Litvaitis, 2004).
- Foodweb analysis predicts loss of insect biomass as large insects on
native plants are replaced by smaller insects on alien trees and
shrubs. Analysis predicts a decrease in insect productivity by over 67%
(Heleno et al., 2008).
- Invasion by the European shrub gorse (U. europaeus) influences the
assemblage of insect and diptera taxa. Assemblage of selected species
was found to change with shrub invasion, with many species being unique
to each habitat (Harris et al., 2004).
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Lesser periwinkle (V. minor) invasion has been shown to change spider
guild, family structure, and abundance through modification of the
forest floor structure (Bultman & DeWitt, 2008).
Charismatic Bird
Diversity and Abundance-
Predation rates for songbirds nesting in multiflora rose were greater
than those for songbirds birds nesting in native shrubs. This is likely
due to reduced nest height and larger shrub volume surrounding the
nests buit within stands of multiflora rose (Borgmann & Rodewald, 2004).
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Invasion by multiflora rose is known to influence the abundance and
distribution of both migratory and frugivorous birds. Depending on
surrounding habitat characteristics, invasion may enhance bird habitat (Suthers et al., 2000; Drummond, 2005; McGranahan et al., 2005).
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For the American robin, dense branch architecture and lowered nest
height led to increased nest predation when birds nested in an exotic
shrub (amur honeysuckle, L. maackii) (Schmidt & Whelan, 1999).
Both of these characteristics are seen in multiflora rose, idicating
robins may experience increased nest predation when nesting in
multiflora rose as well.
Veeries
that nested in barberry (B. thunbergi) had greater success due to the
plant structure (presence of thorns and greater nest height). Indicates
that the invasive form is important (Schmidt et al., 2005).
Historic Landscape-
Due to its ability to form dense monocultures and thickets not seen in
historic landscapes, multiflora rose changes the forest understory in
noticeable ways (www.natureserve.org - Swearingen, pers. comm., 2001; Meiners et al., 2001).