World Biome

Tropical forest biome

• Mostly located between 10oN and 10oS of the Equator

• Latin America (56%) e.g Amazon and Orinco Basin

• Western Africa ( 18%) e.g Congo Basin

• S.E Asias islands and mainland (25%)

Hot desserts

Located 20°- 30°N and S of the Equator

Cover 12% of the land surface

Confined to western side of continents

Northern Hemisphere

• North Africa- Sahara Desert - largest hot desert

• East of the Sahara - desert runs through Saudi Arabia, Iran and Pakistan

• North America - Mexican, Mojave and Colorado Deserts

Southern Hemisphere

• S America - Atacama Desert

• S Africa - Namib and Kalahari Desert

• Australia - Great Australian Desert

Temperate grassland biome

Covers 7% of the land surface

mid-latitude Northern Hemisphere and Southern Hemisphere.

Northern Hemisphere

• 30°N- 50°N centre of continents

• Prairie Grasslands - USA and Canada

• Steppe Grassland - Russia, Ukraine, Kazakhstan, Mongolia and China

Southern Hemisphere

• 30°S-40°S on the eastern side of the continents

• Argentina, SE Australia and South Africa

Tundra biome

Found in extreme high latitudes 50°N to 70°N

• North Alaska, Greenland, north of Canada, Northern Scandinavia, Northern Russia

Temperate grassland temperature + range

Summer - hot at around 20°C

Winter - very cold at around -10°C

Very high at 30°C

Annual precipitation grassland and distribution

Low - 400mm to 800mm

Most precipitation falls in summer months.

Winters much drier.

What is the soil in temperate grasslands

Mollisol

Deep dark topsoil characteristics explained (A horizon)

Black/dark brown very fertile

• annual dieback of deep grass roots adds large amounts of dead organic matter (mull humus)

• Calcium rich loess parent material weathers and adds to soil quickly in hot summer months.

• High fertiiity causes

Nutrient rich-ideal for agriculture:

• August -decomposed organic matter

• minimal leaching precipitation only slightly exceeds evapotranspiration in summer

Calcium nodules in lower A/C horizon

White lumps of calcium carbonated:

• Calcium from weathered loess + its soluble so upward movement by capill

• Poorly developed horizon

Horizon blend together:

Constant alternation of leaching in summer from snow (down) and capillary action (upward). Soil mixing by fauna (earthworms, bacteria etc) because alkaline pH and climate is good.

Clay/ loam texture

Granular and well-structured

Weathering of calcium rich loess

Leaching definition

• Downward movement of dissolved minerals through soil by rainwater, removing nutrients from upper layers when precipitation > evapotranspiration.

Leaching on grasslands

• When & Why (Temperate Grasslands):

  • Spring snowmelt: Low temperature → low evapotranspiration.

  • Summer rainstorms: Intense rainfall → precipitation exceeds evapotranspiration.

• Impact on Mollisol/Chernozem:

  • Slight leaching of calcium from A horizon.

  • Slightly acidic pH when leaching dominates.

Capillary action definition

Upward movement of water through soil pores when evapotranspiration > precipitation.

Capillary action in grasslands

• When & Why (Temperate Grasslands):

  • Summer: High temperature (~20°C) + low rainfall → dry upper horizon → upward water movement.

• Impact on Mollisol/Chernozem:

  • Calcium nodules form in lower A horizon (brought up from parent material).

  • pH ~6–7 (calcium maintains neutral conditions).

  • Poorly defined horizons / absent B horizon due to alternating mild leaching and capillary action, and active soil fauna mixing soil.

Breakdown of organic matter

• Climate Influence:

  • Short growing season, cold winters (-10°C) → grasses die back.

  • Spring warming → active decomposers break down organic litter.

• Impact on Mollisol/Chernozem:

  • High fertility – nutrients from decomposed grasses returned to soil.

  • Deep, dark A horizon – annual dieback adds organic matter; forms mull humus (black/brown colour).

Weathering of parent material

• Climate Influence:

  • Rapid weathering of loess (lime/calcium-rich) during warm, wet summers.

• Impact on Mollisol/Chernozem:

  • Calcium nodules in lower A horizon (from loess).

  • Neutral pH (~7) – calcium acts as a base, neutralising acidity.

  • Poorly defined horizons – calcium maintains neutral pH → active fauna → well-mixed soil.

Tundra biome temperatures + range

Winter - bitterly cold with average temperature of-25°C. Temperature is below 0°C for 6-10 months.

Summer - mild with temperatures of 4°C to 15°C

Large (up 40°C)

Annual precipitation + distribution

130 to 250 mm per year (very low)

All months

Precipitation type in summer and winter

Winter - snowfall

Summer - rainfall

What is the soil in the tundra biome

Gelisol

Permafrost

Subsoil is permanently frozen called permafrost

Summer top 50cm of soil thaws when temp rises

Waterlogged topsoil in summer

Low temp - little evaporation summer water buildup , freezes in colder months.

Little downward movement of water in summer thaw of 50cm because of permafrost

Roots

Permafrost stops deep rooted plants/ trees to grow. Instead lichens, sedges and dwarf shrubs have adaptions to survive

Acidic pH 4.5

dead organic matter - (mor humus) produces acidic, lichen also excrete acids in summer

Peaty undecomposed dead organic matter

Decomposers aren’t active extremely low temps, acidic conditions, waterlogged soils. Accumulation of DOM

• Infertile

• Low input of nutrients - little precipitation (250mm per year)

• Input to soil from weathering of rock is limited due to the permafrost.

Very little biomass litter produced due to:

• Harsh climate - short growing season of 2 months

• Soil permafrost layer 50cm below surface (restrict root development)

• Acidic , waterlogged topsoil in summer restricts plant growth

Slow decomposition of dead organic matter due to low temperatures, acidic and waterlogged conditions few decomposition

No distinct layers/ horizons

Topsoil frozen in winter- subsoil - permafrost

Few soil organism due to low temp; acidity, waterlogging

Dark brown/ black to blue/grey

Dark brown - high partially DOM.

Soil lacks oxygen bcus of water-logging iron in soil becomes deoxygenated and it gives it a blue/ grey colour

Low in nutrients

• Very little biomass because of climate

• The rate of decomposition is very slow Bcus pH

What is the climate change case study

The actual and potenital impact of climate change/ gobal warming on

the tundra biome - Alaskan Tundra

Thawing of permafrost actual abiotic impacts

Permafrost in Alaskan tundra melting for past 50 years - temp increases , rise of 4oC at 1m depth and 2.5oC at 20m deep.

Transportation - roads built on permafrost subside, since 1980s 100 days less travel permitted on permafrost

Thawing of permafrost potential

End of century near surface permaforst almost lost entirely

70% of land vulnerable to subsidence, maintain infrastructure cost up to $6 billion more by 2030.

Drilling of oil easier

Greenhouse gases released when partially decomposed organic matter thaws - starting to break down

Melting of Glaciers actual abitoic impacts

Alaskan glaciers lose 75 billion tonnes of ice each year

More open water in northen areas, in rural alaska cant travel along frozen rivers travel gettind difficult

Increases coastal erosion: alaskas north slope lost 1.5m of coastline annualy to sea erosion since 1950

Melting of Glaciers potential abitoic impacts

disapear by end of century

this will Coastal erosion- threaten villages and infrastructure increase hard engineering for coastlines

e.g Kivalina isolated community of 400 people may relocate cost of $100 million due to coastal erosion.

New sea routes north america for mining oil, increased risk of pollution

poorer water quality actual abiotic impacts

mercury and other chemical pollutants released when permafrost melts - soil erodes.

e.g the Bering Strait becomes acidic

Pooer water quality potential abiotic impacts

Chukchi and Bering seas expected to become acidic

Lakes and wetlands actual abiotic imapcts

Last 50 years in south of alaska where warmer area covered by lakes decreased due to high evapotranspiration

Lakes and wetlands potential abiotic change

increase lake areas

increased wildfires actual abiotic impacts

Summers warmer drier more thunderstorms, larger fires in 2000s since 1940 records, fire in 2007 release carbon dioxide equivalent to which absorbed by tundra over 25 years.

increased wildfires potential abiotic impacts

areas affected by wildfires predicted triple by end of century. fire risk increase as evaportrasnpiration high reduce water avaiable

Actual biotic impact on animals

Species at risk - Pacific walruses, beardes seals. Pacific walruses forced to crowd on Chukchi Sea shoreline bcuc less floating ice in summer.

Land animals e.g caribou, musk oxen struggle for food due to northward expansion of scrub. Caribou rely on lichen in winter which take 50-100 years to recover after burning. Carbiou food source for bears and wolves.

Some speicies thrive in cliamte change e.g Black Brent geese increasing feed on salt-tolearnt vegetation that thrive as permfafrost thaws, coastline erodes adnd salt walter forms.

Potenital biotic impact on animals

permafrost thaws and alters size of lake which disrupts habitats of migratory birds

warming increase jelly fish so decline in fish stocks