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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

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 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