BOT 251 Semester test 1 notes
BIOME CLASSIFICATION
DEFINITIONS:
BIOME: A broad homogenous ecological unit extending over a large natural area and characterised by the dominant life
forms
VEGETATION/BIOME: The structure of the plant life of a region – Refers more to physiognomy of plant life than specific
taxa
FLORA/PHYTOGEOGRAPHY: The plant life of a particular region – Refers more specifically to the taxonomic composition
EXAMPLES OF BIOMES
Biome Dominant life forms Climate Found where? Soils Other
Arctic Tundra All plant life remains Moist Arctic
close to ground. Permafrost in
winter
Water‐logged in
winter
Alpine tundra Mainly grasses, sedges Cold nights, though In high Nutrient‐
and herbs. in summer can get mountains, poor soils
warm above treeline
Extreme weather
Taiga/Boreal Coniferous forests Can
forests Evergreen. photosynthesise
Only few dominant as soon as sun
tree spp., appears
Few shrubs and
groundcover
Temperate forests Deciduous, and much Cold winters, warm
more species‐rich in summers High
terms of animal life precipitation
than taiga
Tropical rainforest Mostly angiosperms Rain most days Hot Soils
and humid often
leached,
therefore
nutrient‐
poor
Others: • Desert • Grassland • Chaparral
• Savanna (Mediterranean,
e.g. Fynbos)
BIOME DISTRIBUTION FACTORS
Climate
Temperature
Rainfall
Seasonality
Influenced by:
o Earth tilt
o Atmospheric heat distribution
o Global climate patterns (latitudinal & continental)
, Soil
Disturbances (fire)
CLIMATE VEGETATION RELATIONSHIPS
• Extreme minimum temperature controls
ever-greenness /deciduousness
• Temperature limit controlling tree growth
polewards (and up mountains)
• Dry winters = drying of grasses in savannas,
which then become flammable
Holdridge diagram:
3 Climatic factors:
1. Annual precip
2. Biotemp (all above 0)
3. Potential evapotranspiration ratio
ADVANTAGES &DISADVANTAGES OF ‘BIOME’ CONCEPT
• Biome is a useful generalised concept
• Allows us to identify comparable areas across the world
• Lack of consistency among world biome maps, and sometimes inconsistent definitions
• In South Africa, biomes are defined as highest level of ecosystem organisation.
SOUTH AFRICAN BIOMES
•Most climate models cannot accurately predict savanna & grassland distribution
•Natural disturbances (e.g. fire) •Biome = (climate + disturbance) life‐form
•Defined based on vegetation characteristics • Largest ecological unit defined
• Distinguished based on dominant plant life form 1st (and 2nd on climate)
• NOT determined based on floristic or phylogenetic composition (do not coincide with phytochoria)
• Based on Raunkiaer type system (location of the renewal buds)
Topography
• Southern tip of the continent
• Steep escarpment
• Inland plateau
• 40% > 1200m ASL
BIOME CLASSIFICATION
DEFINITIONS:
BIOME: A broad homogenous ecological unit extending over a large natural area and characterised by the dominant life
forms
VEGETATION/BIOME: The structure of the plant life of a region – Refers more to physiognomy of plant life than specific
taxa
FLORA/PHYTOGEOGRAPHY: The plant life of a particular region – Refers more specifically to the taxonomic composition
EXAMPLES OF BIOMES
Biome Dominant life forms Climate Found where? Soils Other
Arctic Tundra All plant life remains Moist Arctic
close to ground. Permafrost in
winter
Water‐logged in
winter
Alpine tundra Mainly grasses, sedges Cold nights, though In high Nutrient‐
and herbs. in summer can get mountains, poor soils
warm above treeline
Extreme weather
Taiga/Boreal Coniferous forests Can
forests Evergreen. photosynthesise
Only few dominant as soon as sun
tree spp., appears
Few shrubs and
groundcover
Temperate forests Deciduous, and much Cold winters, warm
more species‐rich in summers High
terms of animal life precipitation
than taiga
Tropical rainforest Mostly angiosperms Rain most days Hot Soils
and humid often
leached,
therefore
nutrient‐
poor
Others: • Desert • Grassland • Chaparral
• Savanna (Mediterranean,
e.g. Fynbos)
BIOME DISTRIBUTION FACTORS
Climate
Temperature
Rainfall
Seasonality
Influenced by:
o Earth tilt
o Atmospheric heat distribution
o Global climate patterns (latitudinal & continental)
, Soil
Disturbances (fire)
CLIMATE VEGETATION RELATIONSHIPS
• Extreme minimum temperature controls
ever-greenness /deciduousness
• Temperature limit controlling tree growth
polewards (and up mountains)
• Dry winters = drying of grasses in savannas,
which then become flammable
Holdridge diagram:
3 Climatic factors:
1. Annual precip
2. Biotemp (all above 0)
3. Potential evapotranspiration ratio
ADVANTAGES &DISADVANTAGES OF ‘BIOME’ CONCEPT
• Biome is a useful generalised concept
• Allows us to identify comparable areas across the world
• Lack of consistency among world biome maps, and sometimes inconsistent definitions
• In South Africa, biomes are defined as highest level of ecosystem organisation.
SOUTH AFRICAN BIOMES
•Most climate models cannot accurately predict savanna & grassland distribution
•Natural disturbances (e.g. fire) •Biome = (climate + disturbance) life‐form
•Defined based on vegetation characteristics • Largest ecological unit defined
• Distinguished based on dominant plant life form 1st (and 2nd on climate)
• NOT determined based on floristic or phylogenetic composition (do not coincide with phytochoria)
• Based on Raunkiaer type system (location of the renewal buds)
Topography
• Southern tip of the continent
• Steep escarpment
• Inland plateau
• 40% > 1200m ASL
