Meet a Tree
Meet a Tree Booklet
The best known member of the forest community is
the tree. What is a tree
and how does it grow? It is one of nature’s marvels.
Trees are the world’s largest plants. They
have a single woody stem, a root
system and a crown of branches and leaves. Each of these parts
a special function or job. The cellulose fibres in the woody stem
tree strength; the roots collect water and nutrients from the soil
them through the stem to the leaves.
The needles or leaves of a tree may be small but
the work they do is
important. They allow the tree to breathe, to release moisture
and to use sunlight to manufacture food through a process called
photosynthesis. This “food”, mostly sugar and other
provides the energy needed for the tree to grow.
The stem, or trunk of the tree, is made up of several
specialized parts. The
heartwood, the non-living core of the tree’s stem, gives
it strength. The
living sapwood surrounds the heartwood. It is through the sapwood
water and nutrients travel, from the roots up to the leaves, where
changed into food by photosynthesis. The downward passage of food
the leaves, to other parts of the tree, occurs in the inner bark.
cambium, the thin yellowish-white layer found between the sapwood
the inner bark, performs the important job of making new cells
allowing the tree to grow. Covering the outside of the tree is
bark, which acts as a protective shell for the tree.
Each tree has its own growth chart. Within the tree’s
structure, the story of
how it has interacted with its surroundings is told. A tree grows
one layer for each year. If you cut through the trunk you will
see the inside
of the tree and the layers will look like rings. The age of the
tree can be told
by counting the rings. Any changes in climate, weather, soil or
affect how the tree grows. Good conditions means the tree will
and the rings will be farther apart. A cold, dry year means less
the rings will be closer together. Trees that are overcrowded will
as they fight for sunlight, moisture and nutrients. Thinning (removing
can prevent overcrowding.
There are 5 major layers of cells within a tree.
Look at page 25, titled “The
Layers of a Tree”, and find the 5 layers. Now read about
This is the oldest part of the tree. Most of the wood in the
trunk of an old
tree is heartwood. The cells are dead and serve to support the
Sometimes the heartwood can rot or be eaten out by animals. When
happens, a large hollow forms inside the tree and it becomes
habitat for a variety of creatures to live in.
Surrounding the heartwood is a layer called the sapwood (or xylem)
made up of straw-like tubes used to transport water and minerals
roots to the rest of the tree. As the sapwood ages, it usually
gets filled with
resin-like material and dies, forming part of the heartwood.
cells are produced by the cambium layer.
Next to the sapwood is a very thin layer of cells called the
cambium. It is
this layer that produces all the new cells in the trunk, making
it grow thicker
each year (palm trees do not do this). On the inner side of the
new sapwood cells are produced. On the outer side of the cambium,
inner bark cells are produced.
INNER BARK (phloem-pronounced floam)
The inner bark cells consist of a series of straw-like tubes
used to transport
sap (containing glucose produced in the leaves during photosynthesis)
the leaves to feed the rest of the tree. It also carries sugars,
stored in the
roots, to the rest of the tree in spring when the tree is starting
to grow again.
It is this flow that is tapped in sugar maple trees to make syrup.
The outside layer on a tree is its bark. Different trees have
textures, and thicknesses of bark but it all serves to protect
the tree from
disease and damage. The bark is made of dead inner-bark cells
pushed farther away from the cambium layers as new inner bark
produced. As the tree pushes outward, the bark often splits and
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