Transcript - Sustainable Learning

Tremendous Trees
From www.sustainablelearning.com
written in partnership with
One Tree per Child
Plants have several basic needs for survival.
These needs include light, water, air, minerals and nutrients. They
also need to be able to reproduce in order to ensure that their
species survives.
Explore how trees have adapted to live in some really challenging
conditions.
Sunlight
How do you think a tree
could be adapted to live in
this darker environment?
In tropical rainforest more than 95% of the light from
the sun is absorbed by the tree canopy making the
forest floor dark.
Adaptation to low light
Plants such as fan palms have evolved to survive in
these gloomy conditions by having big leaves to catch
as much sunlight as possible.
Nutrients
Tropical rainforests
can also have
shallow soils that
are nutrient poor.
How do you think trees might be
adapted to live in areas where
the nutrients in the soil are poor?
In areas where the soil doesn’t have lots of nutrients most trees
have roots near the surface.
But having shallow roots can mean the trees are unstable so some
taller species like bay fig trees have developed buttress roots to
keep them upright and stable.
Water
Some areas in the World can have long periods without any rain.
How do you think trees could be adapted to live in areas that might not have any water
for months?
The Baobab tree which grows in African grasslands
(called Savannah) has developed a huge trunk so that it
can store water in the long hot dry season.
In the UK some of our
own tree species have
adapted to cope with
drier conditions by
having smaller leaves,
such as hawthorn.
Some trees have leaves with
a waxy coating to conserve
water, such as holly.
Cold
Trees even grow in really cold places. Siberia has one of the
densest woodlands, yet temperatures can be as low as -25’C.
How do you think trees are adapted to survive these cold conditions?
Certain trees are great at coping with really cold
conditions. These generally are the conifers which
have needles instead of leaves.
Needles lose less water and have a thick waxy layer
to protect against cold like our native Scots Pine.
Pollution
Trees that live in cities have to survive air pollution
from traffic and industry. In the UK when coal fires
were common, the air in the cities was often thick
with smoke and soot. Only certain species of tree can
cope in these conditions.
An example is London
plane, which is also
common in Bristol. This tree
regularly sheds its bark
which prevented the soot
from harming the tree.
Some trees are excellent for
trapping pollution due to
their hairy leaves. This can
help clean the air. Good
trees for this include silver
birch and lime.
Heat
Certain trees have adapted to survive very high
temperatures that happen during forest fires.
An example is the giant redwood, (or Sequoia) that grow in
California. These amazing trees have unusually thick and spongy
bark, which in some cases, can be more than a metre thick.
This thick bark is fire resistant and
acts like an insulation blanket to
protect the tree from heat. The
oldest Sequoia tree is 3,500 years
old and has different scars from
forest fire burns over the years.
In Europe the cork oak has
a similar thick and spongy
bark.