Tropical Region : Tropical Savanna Grasslands Flashcards
(29 cards)
What are savannas
Areas of tropical grasslands that can occur with or without trees and shrubs
Where are savannas found
Between tropical rainforests and subtropical, high pressure belts
Climate of tropical savannas
Temperatures are high throughout year
Precipitation is low
Seasonal drought common
Location of tropical savannas
Broad band 5-15 degree north and south of equator between tropical rainforests and hot deserts of subtropics
How does climate vary across savanna belts
Towards rainforest boundaries sufficient rain falls to support tree growth. Where as towards desert boundaries only grasses occur in tufts. Drought common
What is the average temperature in savannas
Above 20 degrees highs of 36 degrees,11-13 hours daylight
Total precipitation in savanna
600mm- over 2000mm
What is the drier cooler season known as in tropical savannas ?
Low sun period, sun not overhead but temperatures remain high
Description of savanna soils
Commonly leached, ferralitic soils, similar to rainforest soils
Why does leaching of soils take place in savanna regions
In wet season there is an excess of precipitation over evapotranspiration so soluble minerals leached
What happens to savanna soils in dry season
Evapotranspiration is less than excess of precipitation. Silica and iron compounds carried up through soil
Vegetation in savannas
Grasses, trees and shrubs
What is xerophytic
Plants adapted to drought
What is pyrophytic
Plants adapted to fire
What are some plants adaptations to drought
- Deep tap roots to reach water table
- Partial or total loss of leaves
- Sunken stomata on leaves to reduce moisture loss
What are some plants Adaptations to fire?
- Thick barks and thick budding that can resist burning
- Bulk of biomass being below ground to aid regeneration
- Growth tissue in grasses is located at bottom of shoot so burning/grazing encourages growth
Adaptations of trees for savanna regions
Loosing leaves in drought - reduce evapotranspiration
Small waxy,thorn like leaves , sunken stomata reduce moisture loss
Thick resinous bark protects vascular system
How are acacia and baobab trees adapted
Acacia - deep wide root network “tap” the water to catch water from large area
Baobab - store water in their trunks - trunk is 10 m diameter
How have grasses adapted to drought/fire conditions
- dormant until seasonal rains then grow vigorously
- dry season turn pale straw colour and die back
- most live long time, can be dormant for many years ( drought resistant seeds)
- store food and moisture in root systems
- are pyrophytic As growth occurs from base of stem
What can grasses do after prolonged drought
Have ability to absorb water much more quickly after first rainfall
Herbivores in East Africa have highly specialised eating patterns and can be divided into 2 distinct groups which are?
- Browsers nibble twigs and leaves eg white rhino
- Grazers eat grasses and herbs eg black rhino
How can animals be categorised in the savanna
By selective grazing,allows categorisation depending on height at which they eat eg giraffe feeds from top of tree. Rhinoceros eats lower twigs
Other animal adaptations in the savanna
Animals eat at different times of day and night or year to minimise inter species competition
How so animals respond to prolonged drought in dry season
Small animals hibernate or modify diet by existing in dormant seeds
Birds and most large animals will migrate to search for water and fresh pastures
