The Biosphere- patterns Flashcards
What is the biosphere?
The biosphere is the biologically inhabited portion of the Earth in which ecosystems operate, subdivided into
biomes.
Each region of the biosphere has distinctive…
energy flows, biomass, trophic levels and nutrient cycling
The most obvious structure and patterns are…
…differences in primary production –the amount of
vegetation – biomass (e.g. t or Mg per km2 per
year)
Temperature regime
– Actual temperature and its seasonal pattern is critical for life
– Growing season creates a baseline of food for others
– Adaptability to temperature ranges
Moisture availability
– Local rainfall regime – esp. length of dry season
– Potential evapotranspiration and accessibility to river/groundwater
Zonal factors
– Regional macroclimates (equatorial, monsoonal etc.) correlate to biomes
Azonal factors
– Local environmental factors disrupt an otherwise climatically controlled pattern
– For example, geomorphology and soils affects drainage and aspect
Biomes
Geographical zones with similar ecological communities:
terrestrial, freshwater, marine
Tropical biomes
– Equatorial and tropical forest
– Savanna
– Hot Desert
Temperate biomes
– Mediterranean/chaparral
– Temperate grasslands
– Temperate deciduous forest
– Evergreen temperate forest (southern hemisphere)
Cold biomes
- Taiga (boreal forest)
– Tundra
– Mountains
Tropical rain forest- climate
• Climate
– Mean annual temp ~25°C with little seasonal variation
– 2000 mm rainfall/yr – dry season no longer than 5 months
– Further from equator – increased seasonality
Tropical rain forest- soils
• Soils
– high rates of biogeochemical activity
– Infertile soils, lack of recently weathered rock – oxisols
– Fertility is dependent on continual leaf litter
– Soil type changes with variability in seasonality
Tropical rain forest- High net primary productivity
• High net primary productivity
– 40% global terrestrial productivity
– Degree of seasonality has a large impact on primary
productivity
Tropical rain forest-dynamics
Regeneration
Regeneration
– When natural clearings appear due to fire, wind or water,
species compete for the new niche (especially light)
– Soil erosion and nutrient loss at a minimum
– Mimicked by humans in shifting cultivation
Tropical rain forest-dynamics
Evolution
Evolution
– Associations of vegetation rather than domination by single
species
– High species diversity probably due to amount of energy
and moisture, and age of biome (>100Myr)
– Local specific azonal factors cause high diversity – e.g.
slope, local geology, drainage
– Historical shifts between savanna and forest
Tundra- climate
– Maximum 10oC for the warmest month
– Winter may plunge to −50oC
– Strong, dry, cold winds prevalent, snow accumulates
– Lowland areas characterized by continuous permafrost
– Warmer in coastal regions
Tundra- soils (cryosols)
Soils (cryosols)
– Litter layer of partly decomposed, highly acidic plant matter
– Gleyed horizon overlies permanently frozen layer
Tundra- geomorphology
Geomorphology – very strong immediate influence
– Glacial erosion and current fluvial activity cause shallow
soils
– Underlying sands and gravels left in valley floors – causes vegetation mosaic
Tundra-structure and function
Vegetation
Vegetation
– Three fold structure – low shrub, tussocky grasses, mosses/lichens
– Becomes more simple the more extreme the conditions
– Slow growth
– Most are perennial (grow for longer than 2 years)
– Adapted to reproduction in very short growing season, e.g. bulbs
– Grasses and sedges dominate and dwarf trees, e.g. Betula nana
– Heath dominates on coarser substrate – Erica families
Tundra-structure and function
Animals
Animals
– Migrating animals – causes interesting population dynamics
– Low productivity requires large areas to support migrating herds,
e.g. reindeer
– Hibernation, burrowing and insulating fur/feathers
