The Biosphere- patterns

Question 1

What is the biosphere?

Answer 1

The biosphere is the biologically inhabited portion of the Earth in which ecosystems operate, subdivided into
biomes.

Question 2

Each region of the biosphere has distinctive…

Answer 2

energy flows, biomass, trophic levels and nutrient cycling

Question 3

The most obvious structure and patterns are…

Answer 3

…differences in primary production –the amount of
vegetation – biomass (e.g. t or Mg per km2 per
year)

Question 4

Temperature regime

Answer 4

– Actual temperature and its seasonal pattern is critical for life
– Growing season creates a baseline of food for others
– Adaptability to temperature ranges

Question 5

Moisture availability

Answer 5

– Local rainfall regime – esp. length of dry season

– Potential evapotranspiration and accessibility to river/groundwater

Question 6

Zonal factors

Answer 6

– Regional macroclimates (equatorial, monsoonal etc.) correlate to biomes

Question 7

Azonal factors

Answer 7

– Local environmental factors disrupt an otherwise climatically controlled pattern
– For example, geomorphology and soils affects drainage and aspect

Question 8

Biomes

Answer 8

Geographical zones with similar ecological communities:

terrestrial, freshwater, marine

Question 9

Tropical biomes

Answer 9

– Equatorial and tropical forest
– Savanna
– Hot Desert

Question 10

Temperate biomes

Answer 10

– Mediterranean/chaparral
– Temperate grasslands
– Temperate deciduous forest
– Evergreen temperate forest (southern hemisphere)

Question 11

Cold biomes

Answer 11

• Taiga (boreal forest)
  – Tundra
  – Mountains

Question 12

Tropical rain forest- climate

Answer 12

• 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

Question 13

Tropical rain forest- soils

Answer 13

• 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

Question 14

Tropical rain forest- High net primary productivity

Answer 14

• High net primary productivity
– 40% global terrestrial productivity
– Degree of seasonality has a large impact on primary
productivity

Question 15

Tropical rain forest-dynamics

Regeneration

Answer 15

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

Question 16

Tropical rain forest-dynamics

Evolution

Answer 16

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

Question 17

Tundra- climate

Answer 17

– 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

Question 18

Tundra- soils (cryosols)

Answer 18

Soils (cryosols)
– Litter layer of partly decomposed, highly acidic plant matter
– Gleyed horizon overlies permanently frozen layer

Question 19

Tundra- geomorphology

Answer 19

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

Question 20

Tundra-structure and function

Vegetation

Answer 20

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

Question 21

Tundra-structure and function

Animals

Answer 21

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