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Sector Sampling in R iparian Zones in the Acadian Forest Region. Elizabeth McGarrigle Ph.D. Candidate University of New Brunswick Dr. John A. Kershaw University of New Brunswick. Geometry, hornets, water and trees. Elizabeth McGarrigle Ph.D. Candidate - PowerPoint PPT Presentation
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Sector Sampling in Riparian Zones in the Acadian Forest Region
Elizabeth McGarriglePh.D. Candidate
University of New BrunswickDr. John A. Kershaw
University of New Brunswick
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Geometry, hornets, water and trees
Elizabeth McGarriglePh.D. Candidate
University of New BrunswickDr. John A. Kershaw
University of New Brunswick
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Sampling in Riparian ZonesTypically higher species richness
Slope, drainage, soils - heterogeneityTo capture full range of species, need to
capture full range of growing conditionsSampling high perimeter to area ratioTraditional sampling schemes
Boundary overlap/slop overRequires boundary overlap correction
Alternatives?
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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
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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
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Is Sector Sampling Applicable?Advantages in riparian zones
No boundary overlap correction requiredNo predetermined sampling location required
Possible disadvantagesAzimuth down middle of stand = High number
of treesIs it efficient?
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Overall ObjectiveHow does sector sampling compare with
traditional sampling methods in riparian zones? Ability to quantify:
DensityBasal areaSpecies composition
Options:Implement each method in the fieldTree map riparian zone and simulate sampling
methods
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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/ha26 m^2/ha15 cm quadratic mean
diameter
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The Riparian Zone
Lots of cornersSome dropped tapes4 hornet/bee nests
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Sampling TypesCircular fixed area plots corrected using
walkthrough methodAngle count sampling (ACS) boundary
overlap corrected using walkthrough methodStrip plots perpendicular to streamSector SamplingRiparian zone divided into 6 sections and
sampling types simulated
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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:2m4m
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Point LocationsOn Strip
On each strip one point location on each side of stream6 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 ° angle20 ° angle
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Centered Balanced Sector Plots
Two sizes sampled:10 ° angle/4 = 2.5 ° per
sector20 ° angle/4 = 5 ° per
sector
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Sampling strategyType Small Plot Large Plot Section Sample per
SectionStrip Plot 2 meter full
width4 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 6Centered Sector
Four 2.5° angles
Four 5° angles
All 1 with 4 balanced sectors
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Looking at the DataObserved and predicted graphs of density
and species composition By sectionOverall
Overall basal area Average error over 6 sections
Observed densityObserved species comp
Average error versus number of trees measured
n
poorAverageErr
ii
6
1
2
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DensityBlack – larger plotsRed – smaller plotsGenerally all types
clustered around observed
Plot sizes not significantly different in majority of sections
3/6 sections sector plots are above all other types
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DensityBlack – larger
plotsRed – smaller
plotsBalanced sector
underestimates overall density
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Species CompositionASH – ashBE – beechBF – balsam firGB – grey birchLA – largetooth aspenRM – red mapleSM – sugar mapleSP – spruceSTM – striped mapleWB – white birchWP – white pineYB – yellow birch
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Species Composition by Section
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Species Composition OverallSmall Plots Large Plots
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Basal areaBlack – larger
plotsRed – smaller
plotsACS and Strip
sampling closest to observed
Centralized sector is underestimating basal area
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Average Error of DensityBlack – larger
plotsRed – smaller
plotsCentered sector
has lower error and number of trees measured than single sectors
Strip plots have lowest error
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Average Error in Species Composition
red maple
balsam fir
largetooth aspen
Black – larger plotsRed – smaller plots
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ConclusionsAfter 1050 trees, 4 nests(lots of stings), some
equipment fishing and some simulation…Variability in sector plots in density and species
composition predictionsCentralized sector plots with balanced sectors
performing better than single sectorsStrip plots more accurate in predicting overall
density and require fewer trees measured than other types
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What’s next? Are the results consistent?
Run simulation of sampling scheme againDifferent size sector anglesDifferent configuration for the balanced sectors
3 or 4 sectors per point? Optimal angle to use?
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Questions?
Acknowledgements John Kershaw – Fisherman, nest marker, dog
bringer and simulation coder