Soil drainage impacts frequency but not mode of treefall in a

Transcription

Soil drainage impacts frequency but not mode of treefall in a
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– Should be result statements; concise and meaningful.
No vague generalities.
• E.g., treefall number (generality), Moisture influences
treefall number (concise and meaningful)
Image location in this sample ppt is optional and
purely for example only
Soil drainage impacts frequency
but not mode of treefall in a
temperate deciduous forest
image
Carol K. Augspurger
Department of Plant Biology
University of Illinois
www.webimage.com
Background:
• Important role of treefalls in forest
regeneration
image
www.webimage.com
treefall
Background:
• Types of treefalls: uproot vs. snap off
image
www.webimage.com
Background:
• Soil conditions vs. type of treefall
– Loose
– Saturated
– Interaction with wind
Graph from primary literature
to show preliminary
data helping to generate a question
Augspurger et al. 2007, J. Exp. Bot.
Question:
Does variation in soil drainage
affect the frequency and mode of
treefall?
Hypothesis/Prediction:
• If soil drainage affects treefall frequency
and mode of death,
• then number of treefalls and ratio of
uprooted:snapped-off trees will be
greater in poorly drained than welldrained soils.
Assumption:
• Wind conditions equivalent in both areas.
Methods
• Study site
• Soil drainage: defined and maps
Study site image
Methods
Experimental design
•
IV: Soil drainage (poor or well drained)
•
DVs:
number of treefalls per quadrat
number of uprooted vs. snap off treefalls
•
# replicates: 15 (50x50m quadrats)
•
Sampling unit: one tree > 20 cm DBH
Design image (quadrat placement?)
Methods
• Statistics
t-test (frequency); chi-sq (ratio treefall type)
Example graph
Results
Treefall number depends on moisture
8
Number of treefalls
Number of treefalls
7
6
5
4
3
2
1
0
poorly drained
well drained
Soil type
t-test P<0.01
Results
Mode of death varies among soil types
Treefalls
oftreefalls
Total Number
Number of
60
Red: snap
Blue: uproot
50
40
30
20
10
0
poorly drained
well drained
Soil type
• Chi-sq 1: ratio snap:uproot P>0.05
• Chi-sq 2: uproot>snap P<0.05
Discussion:
• Hypothesis 1: supported
– Why?
– Literature in agreement or not – discuss
or provide evidence (images/graphs)
Discussion:
• Hypothesis 2: not supported
– Why?
– Literature in agreement or not – discuss
or provide evidence (images/graphs)
Minor Limitations
• Pseudoreplication
• Investigator bias
• Variable surrogates
– Light intensity was not measured but
assumed to vary depending on angle of
sun
Future directions
• What can we look into next?
• What will we find based upon your
data?
Conclusions: (summarize the results and draw an encompassing
conclusion in the context of your introduction e.g., climate change, restoration
ecology, spatial dynamics of fragmentation)
• Soil drainage impacts treefall
frequency, but not mode of treefall.
• Areas with contrasting soil should
have different:
•
forest dynamics
•
regeneration potential
•
species composition
Acknowledgments
• TA: Molly McNicoll
• Funding: Mom and Dad
• Institutional Support:
Steve Buck, Manager
Natural Areas/ University of Illinois

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