Biome Distributions

Question 1

What is a biome?

Answer 1

Classification of terrestrial ecosystems using their structure, characterised by same life form.

Question 2

What are examples of biomes that are evergreen/deciduous and needle leaf/broad leaf?

Answer 2

Evergreen, needle leaf: Canadian Alaskan boreal forest
Deciduous, needle leaf: Siberian boreal forest
Evergreen broad leaf: SE Asian rain forest
Deciduous broad leaf: Southern African Savanna

Question 3

Who was Alexander Von Humboldt?

Answer 3

Had Eurocentric, climate centred perspectives on biome distributions, focused on role of climate and soils in determining biomes.

Question 4

What are the ‘rules’ for biome distribution?

Answer 4

1. Environmental filters: survival in cold or dry extremes requires adaptations.
2. Competition: specialists are excluded from warmer/wetter conditions by stronger competitors.

Question 5

What are the temperature ranges for chilling and freezing injury?

Answer 5

Chilling: <10-12 .c
Freezing: <0 .c

Question 6

What are the mechanisms of freezing resistance?

Answer 6

• Metabolic adaptations. e.g. solute accumulation to depress freezing point, antifreeze protein synthesis
• Structural adaptations. e.g. thickening of cell walls, narrow xylem.

Question 7

What are the trade offs between climate resistance and growth?

Answer 7

Cold / dry adapted species are excluded from warm / wet environments by competition

Question 8

What is a tropical savanna biome made of?

Answer 8

Continuous C4 grass ground cover, discontinuous tree cover.

Question 8

What is savannisation?

Answer 8

Deforestation and fires in tropical forests, leads to savanna like vegetation. Often portrayed as degraded ecosystems, targeted for restoration.

Question 9

What are the differences between savannas and forests?

Answer 9

• Savanna:
  Open tree canopy, light understorey
  C4 grasses
  Frequent grass fires
  Fire tolerant trees and adapted ground flora#
• Forest;
  Closed tree canopy, shaded understorey
  No grasses
  No fires
  Non fire tolerant trees and non adapted ground flora

Question 10

What has savanna grass in Madagascar adapted to and why?

Answer 10

Adapted to grazing and fire, evolved in response to now extinct megafauna and is maintained by cattle.

Question 11

How does rising CO2 effect savanna trees?

Answer 11

Rising CO2 promotes growth of savanna trees, promotes C3 trees more than C4 grasses.

Question 12

What are the benefits / negatives of woody plants encroaching on savannas?

Answer 12

Depleting ground water and threatens soil carbon stocks.
Impacts livelihoods: pasture grazing, more animals = more tourism, firewood, charcoal production.