Download Climate Lesson Notes

Climate
Poster 2
Lesson Notes
RAND WATER
RAND WATER
Climate Poster
Hot & Dry
Cool & Damp
POSTER 2
Lesson 1
PHOTOSYNTHESIS
Through the process of photosynthesis, plants absorb energy from the sun and use it to
make carbohydrates from carbon dioxide and water. Carbohydrates are substances
used to produce sugars, starch and cellulose, which are made up of carbon, combined
with hydrogen and oxygen. Plants use carbohydrates as food energy to grow stems,
leaves, flowers and fruits.
TRANSPIRATION PULL
Carbon dioxide enters the plants from the air by way of very small openings in the leaf
surface known as stomata. Carbon dioxide is absorbed through a moist membrane in
the stomata. These stomata open when sun light energy is available. Water evaporates
out of the moist open stomata because of the heat from the sun. This is known as
TRANSPIRATION. Water then moves from the roots up the stems and into the leaves to
replace this loss of water. The force that causes this to happen is called
TRANSPIRATION PULL. Transpiration pull is the initiating force in the path of water in
plants. Deciduous plants use less water in winter because the transpiration pull is less.
(These plants have less leaves or no leaves at this time and thus less stomata.)
Climate - Poster 2 - Lesson 1 - Page 1
People have pores in their skin, which allow them to sweat and thus to keep cool. These
pores are similar to the stomata in the leaf because water is lost through them.
Transpiration in turn also helps the plant to keep cool. Transpiration and perspiration
assist in circulation and cooling processes.
Through the process of transpiration and photosynthesis plants provide:
lAnimals with oxygen (a by product of photosynthesis).
lClean air by removing carbon dioxide (during photosynthesis).
lWater vapour for the water cycle (water loss during transpiration).
OSMOSIS
Osmosis is the process that allows water to move from the soil, through plant root
membranes and into the root system for transportation to the rest of the plant
(transportation pull). Osmosis occurs because the plant roots have a higher
concentration of nutrients and elements than the soil. If we apply too much fertilizer to
the soil we “burn” the plant roots. What happens is there are then more nutrients and
elements (salts) in the soil than in the roots and this causes water to move from the
roots back to the soil through the plant membrane. This is called ex-osmisis
DID YOU KNOW?
lLarger leaf surfaces have more stomata.
lThe hotter the day, the more water
evaporates out of the stomata during
transpiration.
lStomata generally do not open when the sun is not shining. This is because the sun’s
energy is needed to turn the carbon into sugar during photosynthesis.
Notes
ACTIVITY
1. Place a plastic bag over actively growing
leaves.
2. Rub vaseline on the top of leaves. Place in
plastic bag over actively growing leaves.
3. Rub vaseline on bottom of leaves. Place
plastic bag over actively growing leaves.
Note how much water is transpired into
the bag in one day, from the 3 different
experiments.
For experiment to be seen clearly, place
same amount of leaves into each bag. Do
not remove leaves from plant.
Climate - Poster 2 - Lesson 1 - Page 2
SA Rainfall Pattern
LIMPOPO
MPUMALANGA
GAUTENG
NORTH WEST
FREE STATE
NORTHERN
CAPE
KWAZULU
NATAL
LESOTHO
EASTERN
CAPE
Winter Rainfall
Rain all year
WESTERN CAPE
Summer Rainfall
POSTER 2
Lesson 2
LOCAL CLIMATES - SA MAP
Weather
At any given time at any place on the Earth, the lower environment has a particular set
of properties or qualities, namely: temperature, air pressure, humidity, precipitation
(rain), sunlight, cloud cover, wind speed and wind direction. The short-term properties
of the environment are described as the weather of the area.
Climate
Climate, on the other hand, is concerned with the average, long-term weather of an area.
Climate describes the region’s general weather patterns, seasonal variations, and
weather extremes (such as drought or floods) averaged over a long time period of at
least 30 years. The two most important climatic factors of an area are temperature and
precipitation (rain, hail and snow). These two factors determine the type of plants that
can grow in an area, e.g. succulents in a dry climate.
Climate - Poster 2 - Lesson 2 - Page 1
World’s Climate
World’s Vegetaion
Climate - Poster 2 - Lesson 2 - Page 2
World’s Rainfall
Macroclimates
Climate can be studied at different scales. Macroclimates are climates of large areas
such as a village, town or district. The way in which the heat of the sun, and the water on
the planet are distributed around the Earth will decide the macroclimates. The
movement of heat and water are affected by: global patterns of air circulation, ocean
currents, and geographical features such as mountains.
We can identify a few trends in macroclimates. Temperatures decrease as we move
from the equator to the poles. Temperature also decreases with increased altitude or
height. The tops of mountains are colder than their bases. Ocean currents flowing from
the poles to the equator are cold and cause cool dry conditions along the nearby coast.
Warm ocean currents bring heat from the equator. The warm ocean currents warm up
the air above them. This warm air rises to form rain, which makes the coast warm and
wet.
The main climatic regions of the Earth include: (1) the equatorial belt situated along the
equator which is hot and wet; (2) the tropics, which extend to 30 degrees both north and
south of the equator and are also hot and moist; (3) the temperate regions between 30
degrees and 60 degrees in both the northern and southern hemispheres, which
experience mild climates with few extremes; and (4) the polar regions which are cold
and dry.
Climate - Poster 2 - Lesson 2 - Page 3
Some things that affect microclimate
Temperature
Water
Shade trees can lower
the temperature of a
garden.
Water reflects light and
therefore will have a
cooling effect on the air
around it.
Slope
Plants that need more
water should be planted
at the bottom of a slope,
where the rainfall will
collect.
Wind
Sunlight, shade and
position of the house:
The north facing side
of the building will
be warm and sunny,
while the southern
side will be cool and
shady.
Surfaces
Big trees or hedges are
often necessary for
protecting garden
plants against wind and
frost.
Dark, smooth surfaces,
such as tarred areas will
absorb heat and light
coloured or rough
surfaces such as lawn
or cement paving will
reflect heat.
Microclimates
Small variations in climate at the local level are called microclimates. For example,
mountains interrupt the flow of prevailing winds and also produce a rain shadow effect
on their lee-side. Large clusters of trees break up the wind and increase the local
humidity. Buildings and cities alter wind speed and direction, and also increase
temperatures. This is because bricks and concrete first absorb and then radiate a great
deal of heat. We experience these same changes in microclimate in our gardens and at
school.
Understanding microclimates allows the Water Wise gardener to plan and design
his/her garden so as to create microclimates that suit the plants, reducing the loss of
water from the garden. Examples are: planting hedges and groups of plants to create
windbreaks to reduce the effect of hot dry winds blowing into the site; reducing white
reflective north-facing walls will reduce the temperature and evaporation rates from
the hot north side of the garden; planting big hardy trees and shrubs to make shade will
create cool areas for shade-loving plants; encouraging climbing plants to grow up
frames and shade the north side of the house will cool and shade the area; and
channeling runoff from a slope towards a group of thirsty plants will increase the water
supply to plants that need it. Plant deciduous trees on the Northern side of the house.
This will provide shade in summer and allow sun in winter to warm up the house. Most
importantly, Water Wise gardeners should try to create gardens that match the natural
climate of the area.
Climate - Poster 2 - Lesson 2 - Page 4
Climate Poster
Hot & Dry
Cool & Damp
POSTER 2
Lesson 3
PLANT ADAPTATIONS
TO HOT DRY POSITIONS
Oil glands in the leaf reduce evaporation :
Crush and smell the leaf of a plant with aromatic oils, e.g. a Lavender or Rosemary leaf.
These plants come from the dry areas of the Mediterranean and Southern Europe. Oil
evaporates from these glands and remains above the surface of the leaf. This oil
reduces the evaporation of water in the same way as would oil on water in an
experiment. Similarly, when you dip your finger in a volatile oil and another in water,
you will feel a greater cooling affect as the oil evaporates faster than water, causing a
greater cooling effect as more heat energy is lost.
Other common example of plants with volatile oil glands are geraniums and aromatic
herbs such as lemon grass and thyme. Some come from the Mediterranean region
where summers are hot and dry. Local examples can be found among the Fynbos plants
of the Cape. Look just above the surface of these leaves on a very hot day, and you will be
able to see a haze caused by the evaporating volatile oils.
Climate - Poster 2 - Lesson 3 - Page 1
Light colours reflect light, cooling the leaf surface and reducing evaporation:
Dark colours absorb heat, thus controlling the temperature on the leaf surface.
Think about this! Are you cooler in a black shirt or a white shirt. Find a dark
surface and a light surface that are both in the sun. Which one feels cooler?
Leaves which are pale green or grey-green are cooler than leaves which are dark
green. One example is the lavender bush, which is grey. Other plants have a pale
undersurface, e.g. Wild Sage (Buddleja) and Wild Olive (Olea). These plants turn
their leaves upwards in hot weather so that the pale grey undersurface reflects
the sun’s heat away from the plant.
Leaf hairs reduce evaporation:
Expose your skin to the sun. Then cover it with a cloth and feel how much cooler it
is. This is how the hairs on the leaf shade the surface and thereby reduce the
surface temperature of the leaf and so reduce transpiration. Think of a baldheaded man. Does his head sunburn more quickly than a man with thick hair?
The hair on your head is just like the hair on a leaf. A common example of a plant
with hairy leaves is Lamb’s Ear (see poster).
A waxy cuticle reduces evaporation :
Water is also lost from the surface of the leaf between the stomata. If this surface
is covered by wax, then evaporation is reduced. Look at and feel a waxy leaf. It
looks shiny and it feels thick and smooth, (Example: Camelia or Aspidistra or
Sanserveria).
Small leaves:
Small leaves have a smaller surface area for heating and fewer stomata from
which water can evaporate (Example: Acacia spp or thorn trees). Sometimes
leaves are reduced to needle-like structures (Example: Pine trees).
Succulent leaves:
Plants can store water in thick, fleshy leaves (Example: Aloe plants and
succulents ). This fleshy substance in the leaves also aids the plant to moderate
the leaf temperature.
Stomata concentrated on the underside of leaves:
Stomata on the underside of leaves are less exposed to the sun and wind and this
reduces transpiration (Example: Pineapple).
Deep roots:
Deep roots can find water deep in the soil (Example: Fig tree, Camel thorn tree).
Camel thorn tree grows well in dry areas of the Northern Cape.
Succulent roots and stems:
Thick succulent roots and stems store water during dry periods (Example: Iris,
Agapanthus). Plants growing in shade often have spongy root adaptations.
Climate - Poster 2 - Lesson 3 - Page 2
Life cycle strategies for surviving dry periods:
! Annual plants:
Annuals have short life-spans that are completed in one year. They grow, flower
and produce seeds during the favorable periods and then survive dry periods by
producing tough dormant seeds (Example: Namaqualand daisies and Marigolds).
! Bulbous plants:
Lose all their above ground parts and lie dormant underground as bulbs during
their non-growing period (Example: Daffodil, Tulip and Nerine).
! Deciduous plants:
Lose their leaves during the cold dry season to eliminate transpiration and
remain dormant until spring (Example: Stink wood, Oaks, Combretum species).
A rough leaf surface is cooler than a smooth one:
A rough surface heats up less than a smooth surface. To test this find an uneven surface
like a rough gravel road. Compare it to a smooth surface. To make it a fair test, both
surfaces must be the same colour and in a similar position (exposure to sunlight).
Examples of this kind of plant are Buddleja and Sage.
Did you know more information can be obtained by contacting Rand Water on 0860 10 10 60 or visiting Rand Water's Water
Wise web-site : http://www.randwater.co.za
Notes
ACTIVITY
1. Walk around the garden (school
grounds) collecting different plant
leaves. Study them to see if they have
any specific plant adaptations to hot
dry conditions. (You may need to use a
magnifying glass).
2. Walk around outside and identify
microclimate aspects in different areas
of your school grounds.
3. Cut open a leaf of a succulent plant and
compare to any other non-succulent
plant.
Climate - Poster 2 - Lesson 3 - Page 3
RAND WATER
For information and ideas on Water Wise gardening call the
Rand Water customer service centre on 0860 10 10 60,
or visit the home and garden section of their website at
www.randwater.co.za
RAND WATER