Sector sampling in r iparian zones in the acadian forest region
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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

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Sector Sampling in R iparian Zones in the Acadian Forest Region

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Sector sampling in r iparian zones in the acadian forest region

Sector Sampling in Riparian 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

Geometry, hornets, water and trees

Elizabeth McGarrigle

Ph.D. Candidate

University of New Brunswick

Dr. John A. Kershaw

University of New Brunswick


Sampling in riparian zones

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?


What is sector sampling

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


What is sector sampling1

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


Is sector sampling applicable

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?


Overall objective

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


The riparian zone

The Riparian Zone

  • 373 meter stretch of stream

  • 1050 trees stem mapped, diameter measured


The riparian zone1

The Riparian Zone

  • 12 species total (balsam fir, largetooth aspen, red maple)

  • 1400 trees/ha

  • 26 m^2/ha

  • 15 cm quadratic mean diameter


The riparian zone2

The Riparian Zone

  • Lots of corners

  • Some dropped tapes

  • 4 hornet/bee nests


Sampling types

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


Strip plots

Strip Plots

  • First strip randomly placed in first 20 meters


Strip plots1

Strip Plots

  • 2nd and 3rd strips each 20 meters downstream

  • Two size strips sampled:

    • 2m

    • 4m


Point locations on strip

Point LocationsOn Strip

  • On each strip one point location on each side of stream

    • 6 points total

  • Each point:

    • Fixed area, ACS and Sector plots


Circular plots

Circular Plots

  • Two sizes sampled:

    • 3.01 meter radius (1/350th of hectare)

    • 4.61 meter radius (1/150thof hectare)


Sector plots

Sector Plots

  • Two sizes sampled:

    • 10 ° angle

    • 20° angle


Centered balanced sector plots

Centered Balanced Sector Plots

  • Two sizes sampled:

    • 10 ° angle/4

    • = 2.5° per sector

    • 20° angle/4

    • = 5 ° per sector


Sampling strategy

Sampling strategy


Looking at the data

Looking at the Data

  • Observed and predicted graphs of density and species composition

    • By section

    • Overall

  • Overall basal area

  • Average error over 6 sections

    • Observed density

    • Observed species comp

  • Average error versus number of trees measured


Density

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


Density1

Density

  • Black – larger plots

  • Red – smaller plots

  • Balanced sector underestimates overall density


Species composition

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


Species composition by section

Species Composition by Section


Species composition overall

Species Composition Overall

Small Plots

Large Plots


Basal area

Basal area

  • Black – larger plots

  • Red – smaller plots

  • ACS and Strip sampling closest to observed

  • Centralized sector is underestimating basal area


Average error of density

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


Average error in species composition

red maple

Average Error in Species Composition

  • Black – larger plots

  • Red – smaller plots

largetooth aspen

balsam fir


Conclusions

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


What s next

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?


Questions

Acknowledgements

Questions?

  • John Kershaw – Fisherman, nest marker, dog bringer and simulation coder


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