Transcript Australia`s Flora

Australia’s Flora
Year 10
Banksia by Sydney Parkinson (1759-68). Image courtesy of National
History Museum, London.
Australia’s Flora
• Australia’s distinctive flora dates back to a time when the
continent separated from the rest of Gondwanaland: about
30 to 40 million years ago.
• Since then it has evolved in isolation.
• As a result, 80% of all Australian plant species are
endemic.
Endemic:
Flora and Fauna species that do not occur naturally anywhere
else in the world.
Acacias
Eucalypt
Australia’s
Dominant
Vegetation
Casuarinas
Hummock Grasses
Grass Trees
Banksias
Eucalypts
• One of the most dominant and abundant flora
species in Australia is that of the Eucalypt.
• Australia’s eucalypts are well adapted to the
conditions in which they live.
• Their small, hard, leathery and spiny leaves are
an adaptation to low- nutrient soils and dry
conditions.
• Plants whose leaves are adapted in this way are
referred to as sclerophylls
There are 4 main types of Eucalypt forests in Australia:
•
Wet sclerophyll forestsThese generally occupy moist gullies and the southern
aspect of hillsides in areas with relatively high rainfall.
•
Dry sclerophyll forestsThis vegetation type has specifically evolved to suit the
low-nutrient soils, to withstand drought and to
regenerate after fire. This type of forest is a typical
example of ‘the Australian Bush’ as most of us know it.
•
Eucalypt woodlandsAustralia’s woodlands are a combination of Eucalypts and
grasslands; the mix is determined by the local conditions
of aspect, soil and topography.
•
Mallee woodlandsMallees are stunted multi-stemmed eucalypts growing as
small trees, which are adapted to drought and fire. Most
Mallee country has now been cleared for agriculture.
Non- Eucalypt vegetation types
• Acacias are almost as widespread as eucalypts. They
dominate in drier areas.
• Mulga occupies about 20% of the continent.
• Casuarinas have a pine like appearance growing often
along riverbanks and creeks
• Hummock grasses occupy arid and semi arid areas.
Rainforests
• Rainforests once covered
the whole of the continent.
• Today they cover just
0.25 %.
• As the continent drifted to
the north and the
continent’s climate
became drier, the
rainforest vegetation
retreated to the isolated
pockets of land where
rainfall was at least
600mls a year and the risk
of fire was minimal.
Flowering Plants
• Australia’s long period of
isolation has also resulted
in it having some of the
worlds most exotic and
spectacular flowers.
• The international demand
for these flowers has
resulted in an export trade
worth at least $40million a
year.
The Australian Coat of Arms, showing the branches,
leaves and flowers
of the Golden Wattle.
Revision: Account (state
reasons) for Australia being so dry.
• A combination of factors contributes to the dryness of the
Australian continent:
Answer
•
•
•
•
•
dominance of high pressure systems: with dry
subsiding air diverging at the surface, producing fine,
stable weather.
flatness of the Australian continent: absence of any
substantial mountain range except for the Great
Dividing Range which is poorly positioned close to the
east coast preventing moisture penetrating inland.
Compact shape of the continent: no large bodies of
water extending the maritime influence further inland.
Cold ocean currents off the west coast: cooling the
air and reducing evaporation so little moisture moves
onto the continent from the west.
(You may include influence of El Nino: a climatic
variability associated with colder sea temperatures
adjacent to northern Australia resulting in less moisture
coming onto the continent)
Describe (provide characteristics and features) the
features of the physical environment that create such a
unique continent in Australia.
Answer
• Features that may be included:
• The world’s smallest continent and largest island.
• Immense geologic age and stability have resulted in it
retaining many of the oldest things on Earth eg. rocks
and fossils, soils, plants and animals.
• Lowest and flattest of the earth’s landmasses because
of millions of years of denudation.
• Isolation resulted in distinctive flora and fauna with
80% of species endemic to Australia.
• The world’s hottest and driest( inhabited) continent.
• The great age of Australia has resulted in large
deposits of valuable minerals and energy resources.