UNESCO resource kit - science and technology educa...

Healthy conifers
UNESCO Module 9: Forests for the future
Fir and pine trees are covered with needle-shaped leaves. A healthy tree keeps
its needles for three or four years. If the needles drop off when they are younger,
it can be a sign that the tree is unhealthy.
If a tree is losing its needles, or they are going brown, this may be asign that it is
suffering from the effects of pollution. Acid rain can damage the needles, and it
can also damage the tree's roots when it gets into the soil.
Each needle has a waxy outer layer, which helps it to retain moisture. Acid rain
can damage the waxy layer and the needle dries out.
How to tell the age of aneedle
1995
1996
1997
1998
Testing the waxy layer on apine needle
needleofpine drop of water
4 3 2 1
Branch of spruce Abadly-defoliated spruce tree
j1,
zmdamaged
waxlayer
Examine some conifer trees, using the techniques shown above. How healthy
are they?
damaged
waxlayer
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