Comprehensive notes on Terrestrial Biomes

What is a biome?

• A biome is a group of similar ecosystems that have developed in similar climate conditions.
• Biomes are large‑scale ecological communities or ecosystem types.
• They are characterized by their dominant vegetation, climate and other abiotic factors.
• Abiotic factors shape biotic communities.
• Biomes cover large geographic areas and can contain multiple ecosystems within a single biome.
• Major biome groups include:
  • Freshwater biomes
  • Marine biomes
  • Forest biomes
  • Shrubland biomes
  • Grassland biomes
  • Desert biomes
  • Tundra biomes
• Each biome group has characteristic abiotic limiting factors, productivity and biodiversity.
• These groups can be divided further into subtypes, with examples below.

Major terrestrial biome groups (overview)

• Freshwater biomes: ecosystems centered on rivers, lakes, wetlands with freshwater as the dominant medium.
• Marine biomes: saltwater environments (oceans, coral reefs, estuaries).
• Forest biomes: dominated by trees; subdivided into Taiga, Temperate Rainforests, Temperate Seasonal Forests, Tropical Rainforests.
• Shrubland biomes: dense, low-growing woody shrubs with scattered trees, grasses and herbs.
• Grassland biomes: dominated by grasses and herbaceous plants; subdivided into temperate grasslands and savannas.
• Desert biomes: low rainfall; dominated by drought‑tolerant plants and animals; subtypes include hot deserts, cold deserts, coastal deserts, semi‑arid deserts.
• Tundra biomes: high‑latitude, cold environments with permafrost; subtypes include Arctic tundra and Alpine tundra.

Forest biomes and subdivisions

• Taiga (boreal forests)
  • Dominated by coniferous trees; includes cold, expansive forests of the far north.
  • Location: Between 50^
    ightarrow 60^
    ightarrow latitude (north and south of the equator).
  • Example locations: Canada, Russia, Scandinavia.
  • Annual precipitation: $300-900\ \mathrm{mm}$ (spread throughout the year).
  • Temperature range: Winter around $-30^ ext{°C}$; Summer up to $20^ ext{°C}$.
  • Seasons: Two main seasons—winter and summer.
  • Growing season: $2-3\ months$.
  • Soils: Not very fertile; often acidic, with permafrost; shallow soil with a thick litter layer due to slow decomposition.
  • Biodiversity: Less biodiversity than temperate forests.
  • Example flora: coniferous trees.
  • Example fauna: squirrels, bears, reindeer, wolves.
• Temperate rainforest
  • Location: Between 40^
    ightarrow 60^
    ightarrow latitude.
  • Example locations: Pacific Northwest (USA), New Zealand, Chile.
  • Annual precipitation: $2000-3500\ \mathrm{mm}$ (mostly in winter).
  • Temperature range: $5^ ext{°C} ext{ to } 20^ ext{°C}$.
  • Seasons: Mild winters and cool summers.
  • Growing season: $6-12\ months$.
  • Soils: Fertile but nutrient-poor due to leaching.
  • Biodiversity: High biodiversity.
  • Example flora: mosses, ferns, evergreen trees.
  • Example fauna: black bears, elk.
• Temperate seasonal forest
  • Location: Between 30^
    ightarrow 50^
    ightarrow latitude.
  • Example locations: Eastern USA, Europe, China.
  • Annual precipitation: $750-1500\ \mathrm{mm}$ (spread throughout year).
  • Temperature range: Winter $-10^ ext{°C}$; Summer $30^ ext{°C}$.
  • Seasons: Four distinct seasons.
  • Growing season: $4-7\ months$.
  • Soils: Fertile, enriched by leaf litter decomposition.
  • Biodiversity: Moderate biodiversity.
  • Example flora: deciduous trees (oak, maple).
  • Example fauna: deer, foxes, squirrels.
• Tropical rainforest
  • Location: Within the Tropics (0^
    ightarrow 23.5^
    ightarrow latitude).
  • Example locations: Amazon (South America), New Guinea, Southeast Asia, Zaire Basin.
  • Annual precipitation: > $2000\ \mathrm{mm}$.
  • Temperature range: $26^ ext{°C} ext{ to } 28^ ext{°C}$.
  • Seasons: No seasons—hot and wet all year round.
  • Growing season: All year round.
  • Soils: Relatively infertile due to leaching.
  • Biodiversity: Very high biodiversity; ~50% of the world’s plant and animal species.
  • Example flora: mahogany, teak trees, lianas, orchids.
  • Example fauna: toucans, jaguars, frogs, snakes.

Shrubland biomes

• Characteristics: Dense, low-growing woody shrubs, scattered trees, grasses and herbs.
• Distinctiveness: Shrubland is usually classified as a distinct biome and does not fit neatly into either forest or grassland, though it can share characteristics with both.
• Classification nuance: Some systems group shrublands into broader categories depending on ecosystem and dominant vegetation.
• Mediterranean shrublands (e.g., chaparral): Similar to temperate forest biomes.
• Semi-arid shrublands (e.g., savanna‑type landscapes): Closer to grassland biomes.
• Location: Between 30^
  ightarrow 40^
  ightarrow latitude.
• Example locations: Mediterranean Basin, California.
• Annual precipitation: $200-1000\ \mathrm{mm}$ (mostly in winter).
• Temperature range: Winter $0^ ext{°C}$; Summer $35^ ext{°C}$.
• Seasons: Mild, wet winters and hot, dry summers.
• Growing season: $4-6\ months$.
• Soils: Nutrient-poor due to frequent fires.
• Biodiversity: Moderate biodiversity.
• Example flora: shrubs, small trees.
• Example fauna: foxes, lizards, rodents.

Grassland biomes

• Grassland characteristics
• Temperate grasslands
  • Location: (not specified in the provided content).
  • Annual precipitation: (not specified in the provided content).
  • Temperature range: (not specified in the provided content).
  • Seasons: (not specified in the provided content).
  • Growing season: (not specified in the provided content).
  • Soils: (not specified in the provided content).
  • Biodiversity: (not specified in the provided content).
• Savannas
  • Location: Between 5^
    ightarrow 30^
    ightarrow latitude.
  • Example locations: Central Africa (Tanzania, Kenya).
  • Annual precipitation: $800-900\ \mathrm{mm}$.
  • Temperature range: $15^ ext{°C} ext{ to } 35^ ext{°C}$.
  • Seasons: Wet and dry seasons.
  • Growing season: During the wet season ($4-5\ months$).
  • Soils: Free-draining with a thin layer of humus; Fertile but prone to erosion.
  • Biodiversity: Wide range of species.
  • Example flora: grasses, baobab, acacia trees.
  • Example fauna: zebras, elephants, giraffes.

Desert biomes

• Location: Between 15^
  ightarrow 30^
  ightarrow latitude.
• Example locations: Sahara (North Africa), Kalahari and Namib (Southern Africa), Australia, Middle East.
• Annual precipitation: Below $250\ \mathrm{mm}$.
• Temperature range: Daytime up to $50^ ext{°C}$, Night-time below $0^ ext{°C}$.
• Seasons: Summer and winter.
• Growing season: Very short, after rare rainfall.
• Soils: Infertile, dry; Sandy or rocky; low in organic matter.
• Biodiversity: Relatively low biodiversity.
• Example flora: cacti, yucca.
• Example fauna: spiders, scorpions, camels, meerkats.

Tundra biomes

• Location: Between 60^
  ightarrow 75^
  ightarrow latitude.
• Example locations: North of the Arctic Circle.
• Annual precipitation: Less than $250\ \mathrm{mm}$ (mostly snow).
• Temperature range: Winter around $-30^ ext{°C}$; Summer around $10^ ext{°C}$; Below 0°C for $6-10\ months$ of the year.
• Seasons: Winter and summer.
• Growing season: $1-2\ months$.
• Soils: Thin, infertile (low organic matter); permafrost present.
• Biodiversity: Low biodiversity.
• Example flora: small grasses, mosses, lichen.
• Example fauna: snowy owls, snow buntings, tundra swans, arctic foxes, hares, wolves, polar bears, musk ox, caribou.

Distribution of nonmineral terrestrial natural resources

• Nonmineral terrestrial natural resources include resources like water (freshwater) and trees for lumber.
• These resources are essential for human use.
• Distribution varies due to multiple environmental factors:
  • Climate: Temperature and precipitation patterns directly impact water availability and vegetation growth. For example, rainforests are abundant in water; deserts are arid.
  • Geography: Landforms such as mountains and proximity to oceans influence rainfall; rain shadow effects create dry areas on the leeward side of mountains.
  • Latitude and altitude: Higher latitudes and elevations tend to have colder climates, reducing vegetation density and diversity (e.g., tundra vs tropical forests).
  • Nutrient availability: Nutrient-rich soils support denser vegetation; nutrient-poor soils limit growth. In tropical rainforests, rapid nutrient cycling and decomposition in upper soil layers support vegetation despite deeper soils being poor.
  • Soil composition and drainage: Soils with good drainage and nutrient retention support more vegetation than sandy or rocky soils.

Changing distribution of terrestrial biomes (dynamics and drivers)

• The global distribution of biomes is dynamic and has changed in the past and will continue to change.
• Past biome shifts:
  • Natural climate variations (e.g., ice ages) caused shifts in biomes.
  • Example: tundra regions expanded during glacial periods.
• Current and future biome changes:
  • Global warming and rising temperatures are shifting biome boundaries.
  • Biome shifts can occur via two mechanisms:
  • Range shifts: species move to new areas to find suitable conditions as current habitats become less hospitable.
  • Biome type changes: a biome transitions to a different type (e.g., forest → savanna or tundra → forest).
  • Temperature and precipitation are the primary determinants of biome distribution; as temperatures rise, boundaries between biomes shift.

Poleward and elevational shifts under warming

• Poleward movement: warmer biomes (e.g., tropical rainforests, savannas) expand toward higher latitudes.
• Upward in elevation (to higher altitudes): warmer biomes expand up hillsides/mountains.
• Consequences include the contraction of colder biomes (e.g., tundra, boreal forests).

Secondary ecological and societal impacts of biome shifts

• Ecological consequences:
  • Species moving to new areas may face new competition, predation, or disease.
  • Population declines and potential extinctions in some groups.
• Ecosystem services impacts relevant to humans:
  • Water regulation and availability.
  • Nutrient cycling.
  • Carbon sequestration and storage in forests and soils.

Additional drivers and consequences (contextual factors)

• Desertification: Increased droughts and human activities contribute to desert expansion into previously productive lands.
• Deforestation: Loss of forested biomes like the Amazon affects biodiversity and carbon storage.
• Sea-level rise: Coastal biomes (e.g., mangroves, wetlands) shrink as sea levels rise, affecting coastal protection and habitat.
• Implications for policy and land use planning: mitigation of climate change, conservation strategies, and adaptation planning are required to preserve ecosystem services and biodiversity.