The effect of tree density and height
on tree-flagging of Lodgepole Pines
in Niwot’s sub-alpine forest
Michael D. Schuster
Winter Ecology – Spring 2010
Mountain Research Station – University of Colorado, Boulder
Mechanisms of tree flagging
• Predominately carried out by
wind
• Krummholz: “Crooked Wood” in
German; These are the type of
trees/shrubs near or at treeline
• Reasons for bareness of trunk:
lack of SR
In the Big Picture
•
•
•
•
Why is this important?
Useful for forestry practices
Can put in context of CC scenario
Affects passage of mammals
Observations and Hypothesis
• I noticed that the trees had varying heights of bare trunk and
branches, and this general height changed when the trees
were either taller or closer together
• Hypothesis: affected by amount of sun reaching lower
branches, not by krummholz or wind as much
– As the avg height increases, the height of the bare tree will also
increase
– As the L.P. Pine density increases, the height of bare tree should also
increase (more trees-more coverage-less sun to ground)
Methods
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•
•
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10x10 m transect
Clinometer, field tape, flags, snow probe
Total density, density of conifers
Avg height (clinometer), snow depth
Average tree heights of Lodgepole Pines in the Niwot sub-alpine forest
20
18
16
Avg tree height
height (m)
14
12
10
Height of bare tree
8
6
4
2
0
1
2
3
4
Density of trees (# trees per m2)
Average Lodgepole Pine density per
10m2 transect, Niwot sub-alpine
forest
Site # (increasing elevation)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
Site # (increasing with elevation)
5
5
6
6
% of bare tree per change in height
Site 1
y = -0.1213x + 45.267
R² = 0.0002
90
80
Site 2
y = -3.4429x + 87.972
R² = 0.2168
% of tree flagged (with needles)
70
60
Site 3
y = -0.4471x + 48.932
R² = 0.0168
50
Site 4
40
y = -0.1682x + 52.699
R² = 0.012
30
Site 5
20
y = 0.1492x + 61.042
R² = 0.0027
10
Site 6
0
0
5
10
15
total height of tree (m)
20
25
y = 2.9495x + 11.364
R² = 0.1885
% of bare trunk per density of transect
70
P-value = 0.0128
60
% of tree bare
50
40
y = 0.3732x + 38.458
R² = 0.826
30
20
10
0
0
10
20
30
40
number of conifers
Site #
P value
1
0.366941
2
0.037538
3
0.067436
4
0.00619
5
0.010393
6
0.762244
50
60
70
Conclusions
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•
•
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Total L.P. Pine height increases with elevation
Bare trunk height is variable—other factors
Density increases with elevation
% of bare trunk increases with increase in
total height
• No significant results—other variables are
affecting the outcome
Other variables to consider
– Slope of transect
– Aspect of transect (tried to keep this constant)
– Elevation
– Type of forest (are there deciduous trees)
– Amount of exposure (wind
– Snow depth (how does this affect height of bare
tree)
– Inaccuracies with measurements (10 m distance
of transect, from tree, density average)
Suggestions for next time
•
•
•
•
Bring an altimeter, measure elevation
More accurate measurments of snow depth
Find a better way to measure density
Choose transects carefully, controlling for:
– Slope, aspect, exposure, types of trees (no
deciduous)
Finally, for next time: BRING A CAMERA
Works Cited
• Reference articles
Arno, Steven F. Timberline: Mountain and Arctic Forest Frontiers. Chp.1 excerpt, prepared by CU.
New York, 2007.
• Pictures:
– http://www.daviddarling.info/images/vegetation_flagging.gif
– http://www2.swgc.mun.ca/botany/burntisland/images/Flagging%201.
jpg