Different species of trees have different densities and even shapes. The wood of pine and balsa are light. Oak and hickory wood is dense and heavy. Pine trees are tall and relatively thin. Oak trees are tall and broad.
Therefore, the first thing you need to do is determine the kind of tree you are
looking at.
If you know the kind of tree that you are weighing, you can start
weighing your tree.
There are two ways to identify a tree. You can open a tree identification book
and start on the first page comparing your tree with every picture in the book.
If it is a detailed tree book that could take a long time. Some trees are related
and can be confused if you aren't trained to look for the subtle differences.
The faster way is to use a tree identification key.
An identification key groups trees according to their characteristics. The
first two big groups are trees with needles and trees with broad leaves. With
that simple decision, you can eliminate half of the trees in the book. For trees
with needles, the next decision is between scaly needles and longer individual
needles. Again your decision can eliminate half of the remaining trees. After a
few more questions you have identified your tree. There are several good
identification keys on the web that you can use:
ID It
Identification of Common Trees of Iowa
Trees for the
Pacific Northwest
Upper Peninsula TREE IDENTIFICATION KEY
Basics of Tree ID
Finding
a tree’s diameter, height and weight is the second step in weighing your tree.
First, we will find your tree’s diameter. It is hard to
measure through the center of a tree but we can measure the tree’s circumference.
A tree’s circumference becomes smaller the higher up you climb. We need to
agree on a place to measure the circumference. Foresters stand next to the tree
and measure at chest height. Measure
the tree’s circumference. Use the formula Circumference = 2 X pi X radius to
calculate the diameter.
Need help?
Estimating
the height of a tree
From Geometry,
you know that the ratio of 2 sides of similar triangles are equal. Use
this fact to design a method to estimate the height of your tree.
Need help?
Estimating the
weight of a tree
Foresters use algorithms to estimate the green weight of
trees. The algorithms used in this lesson come from “Tables for Estimating
Total Tree and Product Weight and Volume of Major Southern Tree Species and
Species Groups” by Joseph Saucier and Alexander Clark III , Southwide Energy
Committee, American Pulpwood Association Inc., Nov. 1985.
These algorithms are good for the Southeastern United States. The
principle works for any part of the world but the species and growing conditions
vary. If you live in a different part of the United States,
you should contact your county extension agent for trees in your area.
The algorithms require the two measurements you have made:
Diameter at breast height = D, Height of tree = H.
For each kind of tree there are two different algorithms.
One is for trees with a small diameter and a second for trees with a large
diameter.
|
Tree species
|
Size
|
Algorithm
|
|
Southern Pine Coastal plane
|
< 5 inches
|
0.32214(D2H)0.91330
|
|
|
> 5 inches
|
0.19821 (D2)1.06419 (H)0.91330
|
|
Southern Pine
Piedmont
|
< 5 inches
|
0.28557 (D2H)0.92236
|
|
|
> 5 inches
|
0.18703 (D2)1.05385(H)0.92236
|
|
Hard Hardwoods
|
< 11 inches
|
0.38315 (D2H)0.92045
|
|
|
> 11 inches
|
0.11710 (D2)1.16763(H)0.92045
|
|
Soft Hardwoods
|
< 11 inches
|
0.26153(D2)1.12422(H)0.93871
|
|
|
> 11 inches
|
0.10743(D2)1.12422(H)0.93871
|
|
Sweet gum
|
< 11 inches
|
0.24512(D2H)0.95220
|
|
|
> 11 inches
|
0.09605(D2)1.14754(H)0.95220
|
|
Yellow Poplar
|
< 11 inches
|
0.16258(D2H)0.99008
|
|
|
> 11 inches
|
0.12701(D2)1.04157(H)0.99008
|
Hardwood or deciduous trees loose their leaves in the
winter. Some hardwood trees actually have soft wood. Red Maple, Paper Birch,
Aspen
and American Elm are examples of soft hardwood trees. Oak and
Hickory
are hardwood trees that have hard wood. See
list of trees.
These algorithms give you the green or wet weight of the
tree above ground. About 20% of the tree is found in the roots below ground.
Multiplying the green above weight by .2 will give you the weight of the roots.
The total green weight of the tree is the sum of the roots
and above ground weights.
Find the green weight of your tree using:
A pocket calculator and the formulas above,
JavaScript calculators
for the different kinds of trees in
the
Southeastern US,
Ask your teacher if you have access to an Excel spreadsheet
which will help you with these calculations.
Now that you have an answer to the question how much does your tree weigh, we
can look at that answer for opportunities to learn more
about your tree.
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