Lecture 4 CM Flashcards
What is biomass?
the total quantity or weight of living organisms in a given area or volume
What do the interrelated factors determine in biomass?
the kind, abundance and permanence of biomass in any place is determined by a number of interrelated factors
What does biomass reflect?
it reflects circumstances
What does the growth form of plants in any habitat reflect?
it reflects the environmental conditions
- e.g. grass, shrub, evergreen etc
What are formations aka biome?
they are vegetation types that can be classified based on their predominant growth forms
The structure of biomes is predominately governed by?
by the ecology of the dominant plants and vegetation, with the exception of grasslands
What are the roles of plants and animals in ecological processes?
plants are the drivers and animals are the passengers
Globally biomes are seen to have?
- particular proportions of vegetation growth form
- consistent vertical structure
Particular proportions of vegetation growth form examples
- arid or seasonally dry habitats have abundant drought-hardy shrubs
- temperate woodlands are dominated by deciduous tree species
- tropical rainforests have an important canopy epiphyte layer
Consistent vertical structure examples
- single vegetation layer in arctic tundra
- multiple vegetation layers in forest biomes
What are the 9 principal terrestrial biomes?
- Arctic tundra
- Boreal forest/taiga
- Temperate deciduous forest
- Temperate evergreen forest
- Temperate shrubland/Mediterranean scrub
- Temperate grassland/steppe
- Desert
- Tropical seasonal forest/savanna (sub-tropical)
- Tropical rainforest
(10. Mountain biome)
What does the global distribution of the 9 biomes reflect?
they reflect variations in mean temperature and precipitation
What are the 9 biomes distributed at?
they are distributed at specific latitudes within discreet precipitation zones
What is latitude?
it is a reliable estimator for mean annual temperature in terms of intensity of solar radiation and relative proximity to the equator and poles
Precipitation is not correlated with?
Latitude
What is the Hadley cell?
intense solar radiation over the equator drives evaporation and upward convection of air currents, leading to powerful low pressure systems and near constant rainfall at 0-30 degrees N&S of the equator the tropical biome
What is the Hadley cell the principal driver of?
it is the driver of the global weather system
Where does the continual upward convection drive the dry air to?
it drives the dry air int the high atmosphere to the north and south
- some dry air descends at c.30 degrees N&S, giving rise to the dry, hot desert biome
- the remaining air currents continue to move N&S, eventually descending at the poles in the dry, cold polar cell
What is the Ferrell cell?
low lying warm air moving north from the desert biome gathers moisture and collides with cold air moving south from the polar cell
What does the Ferrell cell sustain?
it sustains the cold, moist temperate biome
What do zones of high pressure comprise?
they comprise dry air masses descending from the upper atmosphere (building up air pressure at sea level) and produce little precipitation
- desert regions, polar regions
What do zones of low pressure comprise?
they comprise moist air masses rising into the atmosphere (reducing air pressure at sea level) and produce abundant precipitation
- tropical regions, temperate regions
What drives the latitudinal distribution of biomes over the surface of the earth?
the relationship between the Hadley and Ferrell cell
