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Elizabeth McGarrigle
Ph.D. Candidate
University of New Brunswick
Dr. John A. Kershaw
University of New Brunswick
1
Elizabeth McGarrigle
Ph.D. Candidate
University of New Brunswick
Dr. John A. Kershaw
University of New Brunswick
2
Sampling in Riparian Zones
Typically higher species richness
Slope, drainage, soils - heterogeneity
To capture full range of species, need to capture full
range of growing conditions
Sampling high perimeter to area ratio
Traditional sampling schemes
Boundary overlap/slop over
Requires boundary overlap correction
Alternatives?
3
What is sector sampling?
Developed for use in small patches left after harvest
(Iles and Smith 2006)
Eliminates bias caused from edge effect
No correction required for boundary overlap – plot ends
at boundary
Plot placed anywhere in patch, random azimuth
determined and predetermined angle used to project
plot to stand boundary
Single or balanced sector
4
What is sector sampling?
Developed for use in small patches left after harvest
(Iles and Smith 2006)
Eliminates bias caused from edge effect
No correction required for boundary overlap – plot ends
at boundary
Plot placed anywhere in patch, random azimuth
determined and predetermined angle used to project
plot to stand boundary
Single or balanced sector
5
Is Sector Sampling Applicable?
Advantages in riparian zones
No boundary overlap correction required
No predetermined sampling location required
Possible disadvantages
Azimuth down middle of stand = High number of trees
Is it efficient?
6
Overall Objective
How does sector sampling compare with traditional
sampling methods in riparian zones?
Ability to quantify:
Density
Basal area
Species composition
Options:
Implement each method in the field
Tree map riparian zone and simulate sampling methods
7
The Riparian Zone
373 meter stretch of stream
1050 trees stem mapped,
diameter measured
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The Riparian Zone
12 species total (balsam fir,
largetooth aspen, red maple)
1400 trees/ha
26 m^2/ha
15 cm quadratic mean diameter
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The Riparian Zone
Lots of corners
Some dropped tapes
4 hornet/bee nests
10
Sampling Types
Circular fixed area plots corrected using walkthrough
method
Angle count sampling (ACS) boundary overlap
corrected using walkthrough method
Strip plots perpendicular to stream
Sector Sampling
Riparian zone divided into 6 sections and sampling
types simulated
11
Strip Plots
First strip randomly placed
in first 20 meters
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Strip Plots
2nd and 3rd strips each 20
meters downstream
Two size strips sampled:
2m
4m
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Point Locations
On Strip
On each strip one point
location on each side of
stream
6 points total
Each point:
Fixed area, ACS and
Sector plots
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Circular Plots
Two sizes sampled:
3.01 meter radius
(1/350th of hectare)
4.61 meter radius
(1/150th of hectare)
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Sector Plots
Two sizes sampled:
10 ° angle
20 ° angle
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Centered Balanced
Sector Plots
Two sizes sampled:
10 ° angle/4
= 2.5 ° per sector
20 ° angle/4
= 5 ° per sector
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Sampling strategy
Type
Small Plot
Large Plot
Section
Sample per
Section
Strip Plot
2 meter full
width
4 meter full
width
All
3
Fixed Area
3.01 m. Radius 4.61 m radius
All
6
Angle Count
Sample (ACS)
Metric basal
area factor - 3
Metric basal
area factor – 2
All
6
Sector
10 ° angle
20 ° angle
All
6
Centered
Sector
Four 2.5°
angles
Four 5° angles
All
1 with 4
balanced
sectors
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Looking at the Data
Observed and predicted graphs of density and species
composition
By section
Overall
Overall basal area
6
2
Average error over 6 sections
o
p
1 i i
AverageError
Observed density
n
Observed species comp
Average error versus number of trees measured
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Density
Black – larger plots
Red – smaller plots
Generally all types
clustered around
observed
Plot sizes not
significantly different
in majority of sections
3/6 sections sector
plots are above all
other types
20
Density
Black – larger plots
Red – smaller plots
Balanced sector
underestimates
overall density
21
Species Composition
ASH – ash
BE – beech
BF – balsam fir
GB – grey birch
LA – largetooth aspen
RM – red maple
SM – sugar maple
SP – spruce
STM – striped maple
WB – white birch
WP – white pine
YB – yellow birch
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Species Composition by Section
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Species Composition Overall
Small Plots
Large Plots
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Basal area
Black – larger plots
Red – smaller plots
ACS and Strip
sampling closest to
observed
Centralized sector is
underestimating
basal area
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Average Error of Density
Black – larger plots
Red – smaller plots
Centered sector has
lower error and
number of trees
measured than
single sectors
Strip plots have
lowest error
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red maple
Average Error in
Species Composition
Black – larger plots
Red – smaller plots
largetooth aspen
balsam fir
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Conclusions
After 1050 trees, 4 nests(lots of stings), some
equipment fishing and some simulation…
Variability in sector plots in density and species
composition predictions
Centralized sector plots with balanced sectors
performing better than single sectors
Strip plots more accurate in predicting overall density
and require fewer trees measured than other types
28
What’s next?
Are the results consistent?
Run simulation of sampling scheme again
Different size sector angles
Different configuration for the balanced sectors
3 or 4 sectors per point?
Optimal angle to use?
29
Acknowledgements
John Kershaw – Fisherman, nest marker, dog bringer
and simulation coder
Questions?
30