3.1.6.3 biomes

• Biome

  An area characterized by its vegetation, soil, climate, and wildlife
• Biome

  • Distinctive plants and animals which are in the climatic climax stage of succession
  • There are 5 main types: aquatic, grassland and forest, desert, and tundra
• Main types of biomes

  • Taiga
  • Temperate
  • Boreal forest
  • Tundra
  • Grassland
  • Savanna
  • Tropical rainforest
  • Temperate rainforest
  • Taiga
• Tundra

  • High latitudes, winter very cold, summers are brief and little rainfall, low biodiversity of mosses and grasses, permafrost
• Desert


  • 15 and 35 degrees North and South of Equator, less than 200mm of rainfall annually, very hot in day, cold at night, shrubs and cacti sparsely distributed
• Savanna grassland


  • Subtropical high pressure zone, falling air very dry, preserves equatorial region where there is rising air, fires are more common, tropical wet-dry seasons, low precipitation around 800-900mm annually, temperatures warm all year round
• Soil in savanna grasslands

  • Acidic laterites, seasonal variations in biomass, porous and rapid downward movement of water in wet season, thin topsoil removed exposing layer of iron oxide and aluminium oxide that hardens
• Flora adaptations in savanna

  • Isolated trees like baobab with thick water-storing trunks and branches, small leaves in clusters, long taproots to reach water table, lose leaves in dry season, pyrophytic (fire-resistant), release chemicals to alert other trees of herbivory, spines to deter herbivores
• Fauna adaptations in savanna

  • Migration of mammals like wildebeest + birds with long legs + long wingspan to enable long migrations. meerkats -burrowing underground to avoid heat and predators. Leopards - nocturnal to save energy, camouflage to avoid predators. Elephants - large ears and blood vessels to dissipate heat
• Human activity and impact on savanna grasslands include grazing by nomads and penned cattle, fires to maintain the ecosystem, hunting and poaching, and development leading to population change and demand for resources
• Savanna grasslands cover a large part of sub-Saharan Africa both north and south of the Equator, as well as parts of North Australia and south america
• The savanna zones of Africa are located in the subtropical high pressure zone where falling air is very dry + low pressure zone where rising air is wet, intertropical convergence zone
• Grasslands

  • open regions dominated by grass
  • warm + dry

  savanna grasslands - tropical

  • between tropics + few scattered trees + covers almost half continent of Africa + distinct wet + dry seasons

  temperate grasslands - i.e North America

  • high latitudes
  • little to no veg
  • more variation in temp
  • less rainfall than savanna
• forests

  • dominated by trees
  • 1/3 of Earth
  • contain most of the worlds terrestrial biodiversity
• TRF

  • 10 degrees north + south of equator between tropics of cancer + Capricorn
  • hot + wet all year round
  • lush forests + dense canopies + veg
  • amazon river holds about 1/3 of the worlds remaining equatorial forest
• temperate deciduous forest

  • mid latitudes
  • experience all 4 seasons
  • summer is warm, winter is mild, rainfall all year around
  • deciduous trees lose leaves to cope w winter
• boréal taïga, forest

  • precipitation occurring primaryly in the form of snow
  • summers are short + cool
  • winters long + cold
  • coniferous trees
• tundra

  • high latitudes
  • winter is very cold
  • summers brief
  • little rainfall
  • low biodiversity =mosses + grasses due to permafrost
• deserts

  • 15 degrees + 35 degrees north + south of equator
  • less than 200 mm of precip annual
  • large diurnal range
  • shrubs + cacti = sparsely distributed in soil
• Savanna grasslands found in the southern hemisphere, have a hot and dry climate

  • subsaharan Africa, N+S do equator
  • northern central australlia
• Climate of savanna grasslands

  • tropical wet + dry szn
  • Warm all year around
  • 99% of annual precip falls during went szn
  • low precip of 800-900mm annually
  • temp is highest before wet szn = increases evapotransp = more cloud formation
  • temp is lowest after wet szn = rain clouds reflect insolation back
  • seasonal variation - 35 degrees before wet + 15 degrees after wet
• soils in savanna grasslands

  • acidic, laterites + seasonal variations in biomass due to wet + dry sz
  • rapid downwards moment of water in wet szn = leaching silica from soils + top soil removed
  • layer or rich in iron + aluminium oxides = red colour = baked = laterite cement crust reduces plant growth
• effects of seasonal variation on savanna soil fertility

  • wet szn = greatest infertility in soil
  • dry szn = plant death + litter builds up = thin layer of hummus + optimal conditions for aerobic bacteria = increases decomp
• Savana soil moisture budget

  • wet szn - summer, august + sept = porous soil = increased infiltration + soil moisture
  • october - soil moisture utilisation = evaptransp = higher than precip = drawn up by capillary action
  • dry szn - soil moisture deficit = all soil moisture used up, high evapotransp + no precip
• flora adaptations general like xerophytes

  • long taproots = reach water table
  • shallow root = access shallow ground water
  • pyrophytic = withstand fires
  • drop leaves in dry season
  • thick waxy leaves = reduce evapotransp
• acacia tree

  • thorns + spines deter herbivores
  • long tap + shallow roots
  • low umbrella shade crown = shade roots areas from sun = keep soil moist
  • small waxy leaves
  • tannins
  • symbiotc relationship with giraffes
• candelabra tree

  • branches grow straight up
  • secret toxins
  • white sap causes blisters + blinds eyes
  • growls spines = reduces surface area for water loss
• Grasslands savanna

  • perennial, die during dry season + regrow in wet szn
  • sharp + bitter taste to deter herbivores
  • turn blades away to reduce water loss
  • roots can photosynthesise
• Grazing + agriculture

  • nomads - rotational grazing, penned cattle overnight in corrals, resulting in manure fertilising these areas I.e cattle + goats + sheep’s graze
  • natives + livestock = maintains grasslands + prevent woodlands from growing
  • agricultural expansion + intensification = can cause degradation = reduces vegetation cover + reduces biodiversity
  • woody plants are killed through grazing, therefore animal repellant trees become numeorus