| -
a Science in Schools Project undertaken by
LandLearn in partnership with Shepparton Irrigation
Region Private / Farm Forestry scientists
and farmers, and with students and teachers
from Mooroopna Secondary College and Shepparton
High School. |
Contents:
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1.
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Measurement
in the field - techniques
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2.
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Data
collection
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3.
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Data
analysis and application of monitoring techniques
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1.
Measurement in the field - techniques
Introduction:
Vegetation management on both public and private
land, in farm forestry, native forests, gardens
and parkland provides examples of monitoring techniques
which can be applied with students. Understanding
and applying the techniques used in the field
to measure individual trees and stands provides
students with an insight into the roles and work
of forest and other natural resource management
scientists. Students can collect data and, depending
on the sites available, can use the information
in management decisions for the site.
Students will be able to:
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Learn
and apply different techniques for collecting
data about trees. |
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Estimate
growth rates using data collected over time. |
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Determine
or predict the value of an individual tree
and / or of the stand. |
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Make
recommendations about the management of the
site, the selected species, the appropriateness
for the site, the future of the tree or stand,
etc. |
Equipment:
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Flexible
measuring tape (2 -10m) |
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Surveyor
tape |
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Chalk
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Hard
hats (required if undertaking fieldwork in
public and private forests - bicycle helmets
are a good substitute) |
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Safety
vests may be required in some locations |
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Clinometer
(Students could make their own.) |
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Scientific calculator |
(i) Data collection
- Measurements of a single tree
1.
Tree diameter
The
diameter of a tree provides a measure of tree
performance and is required for estimating tree
volume. To determine the tree diameter we measure
the circumference of the tree at a certain height.
By convention, the diameter of forest trees is
measured 1.3 metres above the ground. This is
called 'Diameter at Breast Height' (DBH).
Measurements are done over bark so the actual
name of the measurement you are taking is 'Diameter
at Breast Height Over Bark' (DBHOB).
When
estimating tree volume it is best to have a value
of 'Diameter at Breast Height Under Bark' (DBHUB).
However for student use DBHOB is more appropriate.
How
to measure 'Circumference at Breast Height'
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Determine
where "breast height" or 1.3 metres
is on you |
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Standing
on the up-slope side of the tree, wrap
the tape around the tree at that height
(careful not to twist the tape) |
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Read
circumference measurement from tape |
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Record
the circumference value in column (a)
on Worksheet A |
Precautions
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Be
sure to read the scale on the tape and
record measurement in centimetres (cm) |
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The
tape must be tightly held around the
tree at right angles to the main stem
and any loose bark removed |
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On
sloping ground always measure the breast
height on the high side of the tree
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Obvious
swellings, distortions or branches at
1.3 metres need to be avoided. Move
the tape 10 cm up and 10 cm down and
take an average reading if there is
a distortion at 1.3 metres. |
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Measure
circumference of the tree to one decimal
place (10th of a centimetre) |
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How
to convert 'Circumference at Breast Height'
to 'Diameter at Breast Height Over Bark'
(DBHOB)
Circumference of a circle is equal to Pi
x d, where Pi is 3.142 and 'd' is the diameter.
Rearranging this equation we have: d = c
÷ Pi, (ie divide the circumference at breast
height values by Pi 3.142).
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Divide
the measured circumference at breast
height values by 3.142 |
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Complete
this calculation |
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Record
'Diameter at Breast Height Over Bark'
(DBHOB) value in column (d) Worksheet
A |
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2.
Tree height
The
height of young trees (up to 6 metres) is easy
to measure using a height-measuring pole or a
plastic pipe marked at 0.1 metre intervals, but
as trees grow, measuring their heights becomes
increasingly difficult.
Total Tree height (Ht) refers to the vertical
height from ground level to the tip of the tree.
Outlined
below are several methods to measure the height
of a tree. Choose a method to measure tree height
and record in column (b) on Worksheet A.
How to measure
the height of a tree:
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Method
1 - Isosceles triangle method
Equipment: right angled isosceles triangle,
spirit level, tape measure
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a)
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Use
an isosceles triangle and move towards
the tree until the top of the tree is
at an angle of 45 degrees from you.
Make sure the base of the triangle is
parallel to the ground. A spirit level
would ensure that this is accurately
done. |
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b)
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Measure
the distance from you to the tree and
add your height. The final answer is
the height of the tree. |
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Method
2 - Eye and fingers method
Equipment: Chalk - and good estimation skills
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a)
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Stand
at the base of the tree with a marker
(chalk), scribe on the tree 2 metres
from the ground. Walk away from the
tree (10 - 20 metres), making sure you
can still see the chalk mark on the
tree. |
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b)
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Raise your arm and using your eye with
thumb and index fingers locate the base
and marker (2m). |
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c)
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Using this spacing estimate the height
of the tree by calculating the number
increments (distance between thumb and
index finger) from base to top of tree.
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Method
3 - Pencil method
Equipment: Pencil, tape measure
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a)
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One
person stands at the base of the tree |
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b)
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The
second person walks away from the tree
until the height from base to tree top
matches the length of the pencil when
held vertically up to the eye. |
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c)
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Without
altering the distance between pencil
and the eye, turn the pencil horizontally,
lining up along the ground, with one
end at the base of the tree. |
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d)
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The
person at the base of the tree then
walks away from the tree until he /
she is standing at the end of the pencil.
Measure the distance form the person
to the base of the tree. This equals
approximately the height of the tree.
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Method
4 - Using a Clinometer
Have students make a clinometer in Maths
or Science.
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3.
Tree form
In
farm forestry the shape of the tree is crucial
in determining log value, therefore it is useful
to document a summary of the tree's form.
One
of many different methods for assessing tree form
is outlined below:
Diagram
from http://www.farmforestline.com.au/pages/6.4_tree_form.html
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| Form
1: |
Perfect
form for the intended use or market
(eg. straight bole, fine branches,
no apparent defects, etc) |
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| Form
2: |
Acceptable form for the intended
use or market but not ideal (eg.
some kinks in stem, evidence of
insect attack, etc) |
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| Form
3: |
Unacceptable
form for the intended use or market.
(eg. severe butt sweep, double
leaders or a forked trunk, evidence
of severe rot, etc) |
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One of the most important form factors in the
production of sawlogs is straightness of the butt
log. If the tree deviates outside a central axis
then the form is likely to be unacceptable for
milling purposes or it will severely downgrade
log value.
Work out the tree form for each tree measured
and record in column (c) on Worksheet A.
4.
Tree Basal Area
Tree
Basal Area (TBA) is the cross-sectional area
(over the bark) at breast height. It is used by
scientists as a measure of tree competition and
is a tool used in managing a farm forest.
Complete
this calculation and record in column (e) on Worksheet
A
5.
Tree volume
The
measurements obtained previously (Tree Basal Area
and Total tree height) can now be used to calculate
volume.
Assuming
the tree has a conical shape, then the following
equation can be used:
Example:
If a tree is 20m tall and 50 cm in DBHOB then
the total tree volume over bark would be 1.31
m3.
Calculate
Volume for each tree and record on Worksheet A.
2
(ii) Data collection - Measuring a stand or forest
of trees
(Refer to Worksheet B)
Two percent of the total forest area is the recommended
sample area, with this area divided into a minimum
of three plots. For example, in a farm forest
of 5 hectares a total area of 0.1 hectares should
be measured. If the plots are 0.02 hectares in
size then at least 5 plots must be measured to
provide a sample of sufficient size.
Calculating
plot area: Plot and measure area (m2) = length
(m) x width (m). If available, GPS can be used
for this Once the plot area has been calculated,
mark out the plot using surveyors tape or similar
markers.
Data
collection
Plot
measurement
| (i) |
Tree
circumference - measure the circumference
at breast height of every tree in the plot
and record data on Worksheet B. |
| (ii)
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Tree
Height - measure the height of every tree
in the plot and record data. |
Note : The following data can be calculated
using "Excel" spreadsheet.
| (iii) |
Tree
Basal Area for each tree
(spreadsheet will calculate this value once
tree circumference has been entered) |
| (iv)
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Tree
Volume calculations for each tree
(spreadsheet will calculate this value once
tree circumference and tree height has been
entered) |
| (v) |
Stocking
rate (stems/ha) = 
(enter this value) |
| (vi)
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Standing
total Tree Basal Area 
(spreadsheet
will calculate this value once total plot
area has been entered)
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| (vii) |
Standing total Volume 
(spreadsheet
will calculate this value once total plot
area has been entered)
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| (viii) |
Mean Annual Increment (MAI) =  |
| (ix)
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Current
Annual Increment (CAI) is the increase in
volume at a particular age and is determined
by annual measurements of standing volume.
Example:
Current Annual Increment at age 3 
CAI = (Volume at age 4) - (Volume at age
3)
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Worksheets:
References:
Rowan Reid & Peter Stephen, 1999 - Australian
Master Tree Grower - The Farmer's Log
Dianne Hanna & Ann Fagan, 2001 - Agriculture
and Land Management Fieldwork Kit - Food and
Agriculture in the Classroom, Department of Natural
Resources and Environment. (available from LandLearn)
S.
Bettens et al, 1990 Forest Science
RIRDC/LWRRDC/FWPRDC Joint Venture Agroforestry
Program, 1997 - Design Principles for Farm
Forestry Victorian Landcare Issue 11 Autumn
1999. Farm Forestry special
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Acknowledgments:
Science
in Schools - Science Partnership Project,
Dept of Education and Training
| Scientists: |
Rhodey
Bowman & Suzanne Johnstone (Dept of
Natural Resources and Environment, Tatura) |
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| Science
Coordinators: |
John
Demeo (Mooroopna Secondary College)
& Lloyd Cowling (Shepparton High School)
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| Science
Teachers: |
Tom
Whipp, Kirsten Gass & Lyn Emmerson (Mooroopna
Secondary College) & Deborah Cooke (Shepparton
High School) |
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| Students: |
from
Year 9-10 Science classes at Mooroopna
Secondary College & Shepparton High
School) |
Land holders - Farm forestry fieldwork
sites : Gary Lawson (Pine Lodge) and
Tom Dumaresq (Undera)
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