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Hemlocks and the Woolly
Adelgid
A presentation by Maximus Thaler,
Carlos Medina and SignePorteshawver
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Invasive Species
Non native species that adversely affect a
foreign habitat
Causes? Defense free space
Enemy free space
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Subject Species
Adelges tsugae- Woolly Adelgid Tsuga canadensis Hemlock Tree
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Life Cycle
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Scope of Research
Bio mechanics focus how does the
adelgid affect water flow?
Plant focus how does the trees
condition (stress levels) affect infection?
Forest focus how will the adelgid
infestation affect the whole forest?
Increasing
Scope
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Research Questions
1 Are light stressed plants more susceptible to
infestation by A. tsugae?
2 Does A. tsugae infestation affect plant
physiology with respect to flow rate of water?
3 What plant species could potentially replace
T. canadensis in the canopy community?
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Q1 Are light stressed plants more susceptible
to infestation by A. tsugae?
Open vs. shaded trees
3 branches per cardinaldirection, chosen
randomly
Numbers of alive and
dead A. tsugae counted
in 5cm segment
Photo provided by Colleen Butler
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Hydraulic Conductance Setup
Courtesy of Bio51 Blackboard Page
Q2 Does A. tsugae infestation affect plant
physiology with respect to flow rate of water?
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Q2 Does A. tsugae infestation
affect plant physiology
with respect to flow rate of water?Pressure Source
Pressurized H2O
Branch Segment
Scale
Photos taken by Carlos Medina
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Q3 What plant species could potentially
replace T. canadensis in the canopy community?
100-m2 sampling plots set up (7.07m x
14.14m) as suggested by Brower et al.
Species within plot determined using keyprovided by Prof. Orians
Photo provided by Colleen Butler Photo provided by Colleen Butler
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Figure 2: The effect of branch radius on specific conductivity (flow rate/pressure) ofT.
canadensis branches (n=10), measured in the laboratory at Tufts University 17
November 2010.
Water flow rate through T. canadensis
depends on branch radius
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Water flow rate is not affected
by adelgid infection
Figure 3: Linear regression of specific conductivity (water flow/pressure) ofT.
canadensis branches infected (n=5) and not infected (n=5) by A. tsugae, measured inthe laboratory at Tufts University 17 November 2010.
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Higher density ofA. tsugae on shaded T. cadanensis plants than on trees in open light
environments
Figure 1: Average total number ofA. tsugae sistens found on plant segments in
shaded (n=72) and open (n=72) light environments at the Fells forest reserve on 3November 2010.
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Pinus may come to dominate in the Fells forest
Figure 4: Average relative density of understory tree
genera in 100 square meter sampling areas (n=6) on 3
November 2010 at the Fells forest reserve. Acer n=13,
Pinus n=30, Tsuga n=12, Betula n=4, Prunus n=2. Error
bars represent one standard deviation from the mean.
Figure 5: Average relative density of canopy tree
genera in 100 square meter sampling areas (n=6)
on 3 November 2010 at the Fells forest reserve.
Quercus n=6, Pinus n=7, Tsuga n=5, Betula n=15.
Error bars represent one standard deviation from
the mean.
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Hypotheses revisited
H1: A. tsugae will be more abundant on light-stressed plants.
Hypothesis supported: Plants in shaded environmentexhibited higher densities of adelgid sistens than plantsin the open
H2: A. tsugae will reduce the ability ofT.canadensis to transport water.
Hypothesis not supported: Rate of water flowdepended only upon the radius of the branch.
H3: Changing abundance ofT. canadensis willalter future community structure.
Hypothesis supported: Pinus is more common inunderstory than in canopy, suggesting it may come to
dominate.
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Future research
To better understand why A. tsugae can
spread so rapidly
To develop a treatment plan for saving
infected trees as well as determining which
trees are most susceptible
To develop a prevention plan to stop the
spread ofA. tsugae
A better grasp on physiology can serve as the
foundation of solutions to these problems.
http://wps.prenhall.com/esm_freeman_biosci_1/7
/1953/500185.cw/index.html
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