savanna grassland

Question 1

facts

Answer 1

cover 20% of earths surface (15% more than rainforests)
dominated by shrubs and trees
two sub-biomes: temperate grassland and tropical grasslands

Question 2

tropical savanna grassland

Answer 2

transitional biome
(a theoretical ecocline: a transition between two biomes where there is no distinct boundry)
cover over half of land in africa
outer reaches of the tropical zone
900 mm of rainfall
dry and wet seasons due to being close to the tropical zone
high temperatures at 30+ degrees
growing season is only in the wet season (around 4 months)
free draining acidic and thin layer of organic humus
not very fertile but has a top fertile layer than can not support deep wooded root plants like trees
typical plant species: baobab, acacia, and grasses
typical animal species: elephants, giraffes and elephants

Question 3

climate - most important factor

Answer 3

hot and warm
distinct wet and dry periods
fires occur in the dry season to maintain the grassland

Question 4

climatic savanna

Answer 4

natural succession
annual fires maintain
trees cannot survive long dry seasons

Question 5

edaptic savanna

Answer 5

soil conditions keep them small
hills and ridges form where soil is shallow
valleys of clay create waterlogged soils

Question 6

savanna productivity

Answer 6

vegitation biomass is 9% of tropical rainforests
npp decreases with dry season and latitude from equator
npp is higher where there are grazing animals as nutrients is recycled through decomposition and defecation
animal productivity is higher than in a tropical rainforest

Question 7

nutrient cycling

Answer 7

stores are more even - less affected by leaching due to less precipitation
seasonal variations
dry season along with natural wildfires creates a short growing season - biomass store is overall 1/3 less than a rainforest
higher transfer of nutrients from biomass to litter at the start of the dry season because trees loose their leaves and grasses die back
litter store is small due to fires - decomposition is slow
transfer to soil is small
soil store is larger - vegetation demand is smaller and uptake is restricted to the wet season

Question 8

savanna soil profile

Answer 8

climate is the dominant factor
up to 2m in depth
porous = rapid water drainage
thin humus layer - only support low lying plants with non-wooded root systems or small roots
acidic with a laterite layer which hardens in the dry season and stops roots from penetrating

Question 9

soil moisture budget

Answer 9

fluctuates
wet season = surplus
dry season = deficit
July, August, September - only months where there is a surplus (Sept) and recharging of ground water (Jul/Aug)
potential evaporation is greater than precipitation inputs for 2/3 of the year

Question 10

general savanna plant characteristics

Answer 10

xerophytic
deciduous trees that loose leaves in summer to conserve water in the dry season
grasses are pyrophytic - fire resistant
grass fires restore nutrients to the soil in the dry season

Question 11

baobab tree

Answer 11

prehistoric plant species
absorbs and stores water in the trunk during the wet season, allowing it to produce nutrient-dense fruits in the dry season – “tree of life”
thick bark to resist fires
long tap roots to reach the water table
few leaves reduces transpiration loss

Question 12

acacia tree

Answer 12

“umbrella tree”
20 meters tall
crown provides animals with shade
and reduces evaporation from the soil
symbiotic relationship with stinging ants - they feed on nectar produced by the tree and make sharp hollowed out thorns to protect from predators
central to life in the savanna – seed pods dropped are eaten by rhinos and monkeys and the bark is made into string by the people of Tanganyika

Question 13

general animal adaptations

Answer 13

each species grazer has a preference of grass which maintains biodiversity
adapted:
migration
hibernation
grazing animals like zebra and gazelle have stripes to create an optical illusion and protect against predators
nocturnal and burrowing – safe from fires in the dry season and avoid predators

Question 14

savanna ecosystem services

Answer 14

water
food
fuel
benefit nomad tribes (Maasai of kenya)

Question 15

human impacts

Answer 15

land use change
landscape fragmentation
climate change

Question 16

land use change - human impact

Answer 16

demand for food increases due to population pressure
45% of savanna populations live in urban areas
removes grasses - disrupts fire regimes and natural wildfires which means nutrients isn’t replenished in the dry season
which then makes the ecosystem unable to support large mammals and creates a positive feedback loop of decline
soil is also eroded by the lack of grasses and desertification takes place

Question 17

landscape fragmentation - human impact

Answer 17

with the growth of urban centers in the savanna, habitats are becoming fragmented
migratory animals lose the large patches of land they need to be able to survive which impacts the predator prey life cycle – seeds are also not dispersed which reduces the growth of new trees in the wet season

Question 18

climate change - human impact

Answer 18

increases the length of the dry season
less precipitation
pressure placed on large migratory animals like elephants which have a small adaptive capability - need a large amounts of fresh water a day to sustain their metabolic demands

Question 19

population change

Answer 19

many in LICs
increased conflict between animals and humans
nomadic communities are becoming more static - livestock grazed in smaller areas leads to overgrazing

Question 20

economic activity

Answer 20

prosperity and development increases - leads to more demands in food and goods - leads to agricultural land use changes

tourism boost can lead to income which can be used to support conservation efforts and national parks - however sometimes these can encourage the illegal trophy hunting of ivory and rhino horn and demand for illegal bushmeat - also disturbs habitats and migratory routes

Question 21

agriculture

Answer 21

commercial farming of cash crops - these non native species then utilize all the water and leave none for native species leading tp a loss of biodiversity
overcultivation due lack of crop rotation and monoculture – soil depleted of nutrients and less nutrients is recycled back into the nutrient cycle to support crops during the dry season
over-abstraction of water for irrigation lowers the water table so plants cannot reach it and large watering holes dry up

Question 22

implications for biodiversity

Answer 22

directly - destroying habitats, fragmenting the land, monoculture, and killing crop raiding animals
domestic species are reducing and replacing native species in the ecosystem
increase in invasive species by outcompeting them
fires are naturally occurring however humans changing the fire regime means that non-pyrophytic plant species are killed

Question 23

implications for sustainability (negatives)

Answer 23

overgrazing and intense agriculture
- soil erosion - no plant roots to hold soil together
- desertification
- monoculture decreases species biodiversity
controlled fires
- humans changed the fire regime which means that non-pyrophytic plants are killed in areas where there wouldn’t be naturally occurring wildfires
- humans preventing fires means that organic build up on the top soil leads to uncontrollable burning

Question 24

implications for sustainability (positives)

Answer 24

game reserves
no settlements, livestock grazing, or farming
hunting is controlled
increase sustainability with lack of human interference