The savanna grassland biome

Question 1

Where is the savanna grassland biome located?

Answer 1

Characteristically found within the tropics on all continental masses.
Often associated with the savanna grasslands of Africa.

Question 2

What is the climate of the savanna grassland biome like?

Answer 2

Seasonal variations in wind direction, precipitation and temperature.
Variations occur with increasing latitude from the equator.
Transitions between the equatorial TRFs - rain expected all year, and hot deserts - minimal precipitation.
Generally - dry season in the cooler period, and a wet season in the hotter period - 90% precipitation falls then.

Question 3

How does the precipitation vary in the savanna grassland biome?

Answer 3

Equatorial TRF margins - 1,000mm+ per year, 10-11 months.

Desert margins - 500mm- per year, 1-2 months.

Question 4

How does the temperature vary in the savanna grassland biome?

Answer 4

Equatorial TRF margins - 22C wet - 28C dry.

Desert margins - 18C wet - 34C dry.

Question 5

What happens regarding pressure in the dry season in the savanna grassland biome?

Answer 5

The subtropical anticyclone moves over the desert margins.
The subsiding (cooler) air of the advancing high pressure prevents convection, giving rise to clearer skies and high daytime temperatures.
The trade winds blow from the high pressure towards the ITCZ, moving the air from the land towards the coasts.
Dry air - north Africa, unpleasant wind with low moisture content is produced - harmattan.

Question 6

What happens regarding pressure in the wet season in the savanna grassland biome?

Answer 6

The ITCZ moves polewards.
Rainfall produced - due to uplift and convection being fed by moist, unstable, tropical maritime air.
Only briefly affected - short wet season with low annual rainfall totals.

Question 7

How long does the wet season last in the savanna grassland biomes which are closer to the equator?

Answer 7

It lasts the time the ITCZ has moved polewards - longer rainy season with higher annual rainfall totals.
Two periods of maximum precipitation - when the ITCZ moves polewards, and when it returns.

Question 8

What are the four distinct periods which can be seen in a soil moisture budget of a savanna grassland biome?
PRACTICE DRAWING A SOIL MOISTURE BUDGET.

Answer 8

Soil moisture recharge.
Soil moisture surplus.
Soil moisture utilisation.
Soil moisture deficit.

Question 9

What is soil moisture recharge, and when does it occur in the savanna grassland biome?

Answer 9

July-early August.
When precipitation first becomes greater than evapotranspiration.
Rainwater begins to fill the empty pores in the soil.
When full, the soil is said to have reached its field capacity.

Question 10

What is soil moisture surplus, and when does it occur in the savanna grassland biome?

Answer 10

Late August-September.
Field capacity - the soil is saturated, and the rainwater has difficulty infiltrating the ground.
Lots of surface runoff - higher river levels in the summer.

Question 11

What is soil moisture utilisation, and when does it occur in the savanna grassland biome?

Answer 11

October.
When evapotranspiration begins to exceed precipitation.
More water evaporating from the ground surface and being transpired by plants than is falling as rain.
Water is also drawn up the soil by capillary action - further evapotranspiration.

Question 12

What is soil moisture deficit, and when does it occur in the savanna grassland biome?

Answer 12

December.
Soil moisture is used up - water deficit.
Plants can only survive by being drought resistant/irrigation.
Lasts until precipitation becomes greater than evapotranspiration in early July - so soil moisture recharge can begin again.

Question 13

What does the savanna grassland biome in northern Ghana show?

Answer 13

A lengthy period of moisture deficit.
A short period of moisture surplus.
Total annual potential evapotranspiration greater than total annual precipitation.

Question 14

What vegetation is featured in wetter savanna grassland biomes?

Answer 14

Tall coarse grasses (elephant grass) with many deciduous trees - tree savanna.

Question 15

What vegetation is featured in drier savanna grassland biomes?

Answer 15

Towards desert margin areas.
Shorter tussock grasses, with bare soil between tufts of grass.
Drought-resistant trees e.g. acacia/baobab.
Known as grassland and shrub savannas.

Question 16

What does the vegetation of savanna grassland biomes do regarding their leaves?

Answer 16

Deciduous - lose leaves in the dry season.
Evergreens are also present - hard, leathery leaves to reduce transpiration losses.
Other plants are microphyllous (small-leaved). for the same reason.

Question 17

Where does a parkland exist, and what is it?

Answer 17

Exists within a tree savanna.
Open grassy land with scattered groups of trees.
Isolated trees have low umbrella-shaped crowns that shade root areas, and reduce soil moisture evaporation.
Xerophytic characteristics (adaptations to dry surroundings).
Dense cell fluids, hard waxy leaves, thorns and protected stomata - all reduce water loss.
Acacia and baobab - tree species.

Question 18

What are the characteristics of an acacia?

Answer 18

Tree savanna - parkland.
Crown structure, often flattened by the trade winds.
Loses its leaves in the dry season.
Pyrophytic - withstands fire.

Question 19

What are the characteristics of a babao?

Answer 19

Tree savanna - parkland.
'Upside-down tree'.
Thick spongy trunk, long tap roots.
Bares leaves for only a few weeks.
Pyrophytic - withstands fire - due to its insulating bark.

Question 20

What are the vegetation characteristics of a grassland savanna?

Answer 20

Shorter grasses and more sparse.
Perennial - dying back during the dry season, and regrowing from root nodules when it rains.
Tussocky - allows them to retain some moisture.
Naturally straw dies down and protects roots.

Question 21

What are the vegetation characteristics of a shrub/scrub savanna?

Answer 21

Many acacia trees, thorn bushes and shot tufted grasses.
Many species generate short stems from a single stock, with deep, branched roots and dormant seeds that compete for water.
Some plants - even the stems are capable of photosynthesis - so plants can have fewer leaves and retain more water.
Some grasses - feathery/wiry, can turn blades away from the strong sun to reduce water loss.

Question 22

How does human activity affect a savanna grassland biome? 2

Answer 22

1. Regular burning.
2. Woody plants are killed by cattle eating their foliage - thorny, animal-repellent plants e.g. acacia, therefore become numerous.

Question 23

How does the burning of the grassland work in a savanna grassland biome?

Answer 23

Done to ensure better growth of young grass for the next season of grazing.
Regular burning makes it difficult for young trees/bushes to become established.
Their place is taken by herbaceous and pyrophtic plants e.g. acacia and baobab.

Question 24

What is the extent of human activity on a savanna grassland biome?

Answer 24

Belief that humans have had a much greater influence than climate on the development of savanna vegetation.
Suggestions that grassland may therefore not be the climatic climax community.