It is important that students understand the biology
of trees to further be aware of trees’ role in the
ecosystem
throughout
How to
Measure &itsIDlife.
Week 1 Day 3
Seedling
Seed
Sapling
Snag
Mature
Oak
Like all living things trees have a life cycle:
 Birth
 Growth
 Aging
 Death
As trees grow, their physical form changes as
does their role in the forest ecosystem
Which came first - the
tree, or the seed?
 Seeds come in a variety of shapes,
weights, colors, and sizes, depending on the species.
 Seeds develop from male and female parts of the trees
producing fruits.
 Some seeds are in a protective nut like an acorn
 Others are in fleshy fruits, like the black cherry.
 The fruit of a pine is a cone and the seed is winged and
resembles a miniature helicopter when falling.
 Wind, water, animals, and people disperse seeds to the
forest floor, open fields, yards and roadsides.
 Where conditions are favorable for germination, seeds
will germinate and grow.
 The seedling grows and begins to
develop woody characteristics.
 The stems harden, change color, and
develop a thin protective bark.
 The stem may bend or develop branches
that reach toward light.
 Leaves or needles that develop are
adapted to shade, but lean or tilt toward
light.
 Most roots are in the upper soil to
absorb water, nutrients and air.
 Seedlings compete for nutrients, water,
sunlight, and space.
 Threats include fire, flood, drought,
disease, insect attacks, and animals.
 At this stage the tree is most susceptible
to being killed.
 When the tree is about 1-4 inches in
diameter at 4.5 feet, it is considered a
sapling.
 standard height where tree’s diameter is
measured – diameter at breast height (DBH).
 As the tree starts to get taller the trunk
thickens and branches develop.
 A sapling is the size of a tree growing in a
nursery.
 In this juvenile state, the tree is not
mature enough to reproduce.
 Growing rapidly, the sapling has the
same competition and threats as
seedlings.
What does DBH mean?
With favorable conditions, a sapling will grow
into a mature tree (>4 inches DBH).
During this stage, each tree will grow as much
as its species and site conditions will permit.
In addition, flowers develop, reproduction
ensues, fruits form, and seed dispersal can
now occur.
Trees provide the maximum environmental
benefits to people during this stage.
What plant in the picture
would you say is a
mature tree?
The life span of a tree is a wide-range, yet
death is inevitable.
A combination of factors overcome a tree and
causes it to die.
 Injury, drought stress, followed by disease, rot,
root dieback, coupled with a lightning strike or
insect infestation contribute to tree decline.
Sometimes a single factor is serious enough to
cause mortality.
 Standing dead trees, called snags, play vital
roles in the life cycle of many organisms.
 A snag slowly breaks down and returns
nutrients as limbs, bark, and branches fall. It
provides habitat and food for wildlife and
insects.
 Animals, insects, and fungi help break down the
tree.
 Eventually, the snag will fall and return
nutrients to the soil where they are taken
up by other trees.
 And, the cycle begins anew.
What stage of the
lifecycle are these trees
in currently?
SEEDLING 
What stage of the
lifecycle are these trees
in currently?
SNAG 
What stage of the
lifecycle are these trees
in currently?
SAPLING 
Have you ever measured
anything? WHAT? HOW?
WHY?
Why do people measure
things?
In what ways do people
measure things?
How many finger lengths
is your book?
1. Use the length of your index finger to
measure the width of you textbook.
2. Use the length of your forearm to
measure the height of your desk.
Why did people get
different measurements?
Compare your index
finger with your
neighbors.
Record the results in your packet.
How can we make sure
our measurements are
accurate?
 Plan harvesting
 Make forest management decisions
 Monitor forest health
 Tree diameter is an important forestry measure and is used
to indicate how well a tree is growing over time.
 It is also one of the standard measures of timber volume
used to estimate the commercial value of a forest stand.
 By convention, the diameter is measured at a height on the
trunk that is 1.35 m (4.5 ft) above ground level.
 This height above the ground is used because uneven
swelling and irregular growth at the base of the tree and
upper roots could mask the true growth of the trunk.
What would happen if
people measured tree
circumference at
different heights?
What is the crown
spread of this tree?
2.5 feet
 This is a horizontal measurement:
 leaf tip to leaf tip of the shortest spread
 leaf tip to leaf tip of the longest spread
 through the main mass of the tree canopy
3 .5 feet
Add the two numbers together, and divide by two for the
average crown spread
1 .5 feet
 Crown spread is difficult to measure when branches
are high. Have 2 people stand where the tips of the
farthest branches are directly overhead. A 3rd person
can measure the distance at ground level.
What is the crown
spread of this tree?
9.5 feet
11 feet
8 feet
 What characteristics would you use to identify
trees? Look at the twigs on your desk for ideas.
 Look at several different features
 Leaves
 Bark
 Twigs
 Flowers
 Fruit
 SeedsHow do you think
 Shapeyou use a book like
this to identify
trees?
 In the simplest sense we have 2 types of trees:
 Conifers (coniferous) :
 seeds develop in cones, have needle shaped leaves
 don’t lose leaves each year so stay green = evergreens
 Pines, spruces, hemlocks and firs
 Broad-leaf (deciduous) :
 broad, flat leaves that they lose each year
 Oaks, maples, beeches and aspens
Differ in many ways and help identify trees
Tips may be pointed, rounded, tapered…
Bases may be squared, rounded, heartshaped…
What are the
shapes of these 3
leaves?
1
PALMATE!
HEART-SHAPED!
2
3
ROUND OR OVAL!
Edges or margins of leaves give clues to tree
identity
 Teeth (serrated)
 Lobed
 Smooth (toothless)
What type of leaf
margin do these
leaves have?
LOBED!
Completely hairy
Hairs on one side
Completely smooth
Thick, thin, rough or waxy
 Simple leaves have
only one piece to them
 Maple, oak, aspen and
sycamore
 Compound leaves are
made-up of several
leaflets
 Ash, walnut and sumac
trees
Are these leaves
simple or
compound?
3
2
1
5
4
6
The way the leaves are arranged on the twigs
 Alternate, opposite, whorls
What kind of leaf
arrangements are
these?
ALTERNATE!
 Even leafless twigs can help identify trees.
 Look for the leaf scars (leaves used to be there) or buds
on the twig to see if leaves grow alternate, opposite or
whorled.
 Size, color, texture, and shape of buds also help identify
trees.
 Spines, thorns, prickles and other surface features also
help.
What type of leaf
scar pattern do
these twigs show?
2
OPPOSITE!
1
ALTERNATE!
 Various tree species
produce characteristic
fruits.
 Deciduous tress produce
berries, winged samaras,
nuts, or drupes. Some
have unique names
(acorns, walnuts, and
chestnuts).
 Conifers produce
different cones that vary
in shape, size, and
arrangement of scales.
Identify with the color and texture
Shaggy, smooth , rough or deep furrows
Example: Paper Birch – white, paper-like
Use bark on trunk, not branches
Paper Birch
 Characteristic shapes can identify trees
 Rounded, weeping, vase-to Funnel, tabular and conical
 Some people are able to look at a tree in the distance and
know what kind it is