Forest Inventory_FOR 480

8/4/2019 Forest Inventory_FOR 480

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Source: J. Hollenbeck

Fixed Area Sampling

Avery and Burkhart,

Chapter 10

FOR 220 Aerial Photo Interpretation and Forest Measurements


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Plot Cruising

Fixed Area Plot Sampling



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Nominal cruise intensity

How much of the land was

sampled?

Examples:

1/10 acre plot on a 2 x 5

chain spacing:

(remember 10sq. ch. = 1 ac.)

100plotbydrepresenteAcres

acresinsizePlot

=I

10%1001

0.1=

=I

Plot Cruising




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Plot cruise planning:

120 acre tract

10% cruise (sample)

1/10 acre plots

( )percent(cruisearea)TractsampledArea =

acres12.0(0.1)ac)(120sampledArea ==

Plot Cruising



1. Area to be sampled:

Given


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Plot cruise planning:

120 acre tract

10% cruise (sample)

1/10 acre plotsarea sampled = 12.0 ac.

=

areaplot

sampledAreaplotsofNo.

plots1200.1

12.0plotsofNo. =

=

Plot Cruising



2. No. of plots needed:.


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=

plots

areaTractareativeRepresenta

ac1plots120

acres120areativeRepresenta =

=

Plot Cruising



3. Samples represent how much area?


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=

linesbetweenDist

areativeRepresentaplotsbetweenDist

=

plotsbetweenDist

areativeRepresentalinesbetweenDist

( )linesbetween(Distplots)betweenDistAreativeRepresenta =

Plot Cruising



4. Plot spacing?

Distance between plots


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=

ft200

ftsq43560plotsbetweenDistance

ft)(200plots)between(distance=ftsq43560

Plot Cruising



5. Plot spacing?

Distance between lines

( )linesbetween(Distplots)betweenDistAreativeRepresenta =

feet215~plotsbetweenDistance =


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Some advantages of plot cruising:

1. Suitable for one-person cruising.

2. Cruisers do not have to tally trees while following a compass

line.

3. Cruisers pause at plot centers, allowing more time to check

measurements.

4. Tree tally is separated by plots: can separate the plots into

sets to calculate volumes for different timber types, etc.

Plot Cruising




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Purposes:

To evaluate regeneration status

To demonstrate compliance with laws

To determine effectiveness of regeneration treatmentsTo identify additional treatments needed

To collect data to predict growth and yield

Regeneration Plots

Fixed Area Plot Sampling - Different plots for different purposes


Plot-count method (number of trees per acre)Stocked-quadrat method (proportion of land utilized) Staked-point method (like permanent plots)


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Nested Circular Plots

Smaller Trees Measured on Smaller Plots


Area

(ac)

Area

(ac)

Radius(ft)

1/500 0.002 5.3

1/100 0.01 11.8

1/10 0.1 37.21/10 acre plot

1/100 acre plot

1/500 acre plot

Trees > 5 inch dbh

Trees 2 to 5 inch dbh

Trees < 2 inch dbh


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Plot Sampling with


Plots and Product Groups

1/10 acre for sawtimber, poletimber, invasive ( 5 in)

1/100 acre for small trees

1/500 acre for advance reproduction

TwoDog Product Groups

Code Product Group

1 Sawtimber ( 12 inches dbh)

2 Poletimber (5 in dbh < 12 in)

3 Small Trees (2 in dbh < 5 in)

4 Advance Reproduction ( < 2 in dbh)

5 Invasive Species


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Source: J. Hollenbeck

Point Sampling


Avery and Burkhart (2002)

Chapter 11


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A method of sampling based on a trees size, rather than

its frequency of occurrence.

Tools: prisms, angle gauge, Relaskop

The probability of tallying a tree depends on its cross-

sectional area and the sighting angle used.

The smaller the sighting angle, the more trees included in

the sample.

Point Sampling

Point Sampling



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Point Sampling


Point Sampling(Overhead view)

Each tree has a

given plot size in

relation to itssize.

How many of

these plots does

our point fall

into?


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Point Sampling

Point Sampling(Side view)


?

Offset tree bole in prism has no

overlap with actual tree bole

Offset tree bole in prism

does overlap actual tree bole

Borderline tree - must

measure distance from

point center

Using a prism:


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Fixed plot sampling Point sampling

Expansion factor Same for all trees Varies by tree

Sampling is based on.. Frequency of occurrence Tree size

Point Sampling

Comparing Point Sampling and Fixed Area Plot Sampling


PPF PPS


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Point Sampling

Important Ideas about Point Sampling

1. Basal Area Factor (BAF)

How much BA does each sampled tree represent?

2. Plot Radius FactorHow far away can a tree be and still be sampled?


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Basal area factor (BAF)

Related to the sighting angle size of the prism used in

point sampling.

Chosen to provide a tally of 5 - 12 trees per point (8-10)

Eastern U.S.: 5, 10, 20

Western U.S.: 20, 40, 60

Point Sampling



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Calculating basal area from a point cruise:

acreft.sq.80.81025

202BA /=

=

Example:

BAF 10 prism 202 trees tallied 25 points

BAFpointsofnumber

talliedtreesTotalBA

=

Point Sampling


It really is that easy!!


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Plot radius factor (PRF)

The value to use in determining the maximum distance a tree of a

given diameter can be from the point to still be tallied.

For example, when using a BAF 10 prism, the plot radius

factor is 2.75.

Point Sampling


Which means:

For each inch of dbh, a tree can be 2.75 feet from the point to still

be included in the points tally.

Thus a 12 inch tree can be up to 33 feet (12 x 2.75) from the point and

still be included in the points tally.


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Nested Plots

Point Sampling


10 BAF Prism Sample

1/100 acre plot

1/500 acre plot

Trees > 5 inch dbh

Trees 2 to 5 inch dbh

Trees < 2 inch dbh


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What about TwoDog?

Plots and TwoDog Product Groups

Prism or 1/10 acre plot for sawtimber, poletimber, and invasive

( 5 in)

1/100 acre for small trees

1/500 acre for advance reproduction


Code Product Group





5 Invasive Species


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TwoDog Product Groups and Products


Code Product Group





5 Invasive Species

Two Dog Products

Code Product

PS Pine Sawtimber ( 12 inches dbh)

01 Grade 1 Sawtimber ( 12 inches dbh)



TT Tie and Timber Grade ( 12 inches dbh)C Cull ( 12 inches dbh)

PT Pole Timber (5 in dbh < 12 in)

SM Small Trees (2 in dbh < 5 in)

R0 Reproduction < 1 ft tall

R1 Reproduction 1 to 2 ft tall



R4 Reproduction > 4 ft tall, < 2 in dbhIT Invasive Trees ( 5 inches dbh)

IS Invasive Small Tree (2 in dbh < 5 in)

IR Invasive Reproduction (< 2 in dbh)


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What about snags?


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What about snags?

Forest Inventory_FOR 480

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