1.2 Terrestrial Biomes

What Are Biomes

  • Biomes are large-scale ecological regions made up of similar ecosystems.

  • They develop under similar climate conditions, especially temperature and precipitation.

  • Biomes are characterized by:

    • dominant vegetation

    • climate

    • abiotic limiting factors

  • These abiotic factors shape the biotic communities found there.

  • Biomes cover large geographic areas.

  • Multiple ecosystems can exist within a single biome.

Key idea

  • Biome = climate + vegetation + adaptations

Major Biome Categories

  • Forest biomes

  • Shrubland biomes

  • Grassland biomes

  • Desert biomes

  • Tundra biomes

  • Freshwater biomes

  • Marine biomes

Each biome group has characteristic:

  • abiotic limiting factors

  • productivity (NPP)

  • biodiversity levels

Distribution of Terrestrial Biomes

  • Biome location is mainly determined by:

    • Temperature

    • Precipitation

  • These are controlled by:

    • latitude

    • altitude

    • insolation (solar energy)

    • geography (mountains, oceans)

Insolation

  • More direct sunlight at the equator

  • Less sunlight toward the poles

  • Affects temperature and photosynthesis

Precipitation

  • Determines water availability

  • Major limiting factor for plant growth

Key rule

  • Temperature + precipitation = biome type

Forest Biomes

Taiga (Boreal Forest)

Location

  • 50°–60° latitude

  • Canada, Russia, Scandinavia

Climate

  • Long, cold winters; short summers

  • Precipitation: 300–900 mm (mostly snow)

Growing Season

  • 2–3 months

Soils

  • Acidic, nutrient-poor

  • Slow decomposition

  • Often underlain by permafrost

Vegetation

  • Coniferous evergreen trees (pine, spruce, fir)

Biodiversity

  • Low to moderate

Key AP points

  • Largest terrestrial biome

  • Important for carbon storage

  • Vulnerable to climate change

Temperate Rainforest

Location

  • 40°–60° latitude

  • Pacific Northwest, Chile, New Zealand

Climate

  • Mild temperatures

  • Very high precipitation (2000–3500 mm)

Growing Season

  • 6–12 months

Soils

  • Nutrient-poor due to leaching

Vegetation

  • Evergreen trees

  • Mosses and ferns

Biodiversity

  • High

Temperate Seasonal Forest (Deciduous Forest)

Location

  • 30°–50° latitude

  • Eastern USA, Europe, China

Climate

  • Four distinct seasons

  • Precipitation: 750–1500 mm

Growing Season

  • 4–7 months

Soils

  • Fertile due to leaf litter decomposition

Vegetation

  • Deciduous trees (oak, maple)

Biodiversity

  • Moderate

Key AP point

  • Trees lose leaves to reduce water loss in winter

Tropical Rainforest

Location

  • 0°–23.5° latitude

  • Amazon, Congo Basin, Southeast Asia

Climate

  • Hot and wet year-round

  • No seasons

Precipitation

  • Over 2000 mm annually

Growing Season

  • Year-round

Soils

  • Nutrient-poor due to rapid nutrient cycling and leaching

Vegetation

  • Broadleaf evergreen trees

  • Multiple layers (canopy, understory, forest floor)

Biodiversity

  • Highest of all terrestrial biomes

  • ~50% of global species

Key AP points

  • Highest NPP

  • Heavily threatened by deforestation

Shrubland Biome (Chaparral)

Location

  • 30°–40° latitude

  • Mediterranean Basin, California

Climate

  • Hot, dry summers

  • Mild, wet winters

Precipitation

  • 200–1000 mm (mostly winter)

Soils

  • Nutrient-poor

  • Frequent fires

Vegetation

  • Dense, woody shrubs

  • Fire-adapted plants

Biodiversity

  • Moderate

Grassland Biomes

Temperate Grassland

Location

  • Interior continents

  • Prairies, steppes, pampas

Climate

  • Hot summers, cold winters

Precipitation

  • 250–750 mm

Growing Season

  • 3–4 months

Soils

  • Very fertile (mollisols)

Vegetation

  • Grasses and wildflowers

Key AP points

  • Maintained by fire and grazing

  • Frequently converted to agriculture

Savanna (Tropical Grassland)

Location

  • 5°–30° latitude

  • Africa, South America, Australia

Climate

  • Warm year-round

  • Distinct wet and dry seasons

Precipitation

  • 800–900 mm

Growing Season

  • Wet season only

Soils

  • Fertile but prone to erosion

Vegetation

  • Grasses with scattered trees (acacia, baobab)

Key AP points

  • Fire and grazing maintain structure

  • Supports large herbivores and predators

Desert Biomes

Location

  • 15°–30° latitude

  • Sahara, Mojave, Gobi, Australia

Climate

  • Very low precipitation (<250 mm)

  • Extreme temperature variation

Soils

  • Dry, sandy or rocky

  • Low organic matter

Vegetation

  • Drought-adapted plants (cacti, succulents)

Biodiversity

  • Low

Key AP points

  • Lowest NPP

  • Vulnerable to desertification

Tundra Biomes

Location

  • 60°–75° latitude

  • Arctic regions, high elevations

Climate

  • Extremely cold

  • Long winters

Precipitation

  • <250 mm (mostly snow)

Growing Season

  • 1–2 months

Soils

  • Thin, infertile

  • Permafrost present

Vegetation

  • Mosses, lichens, grasses

Biodiversity

  • Low

Key AP points

  • Permafrost limits root growth

  • Thawing releases methane

Biome Shifts and Change

Natural Changes

  • Ice ages caused historical biome shifts

  • Tundra expanded during glacial periods

Human-Caused Changes

  • Global warming

    • Biomes shifting poleward

    • Biomes shifting upward in elevation

  • Desertification

    • Expansion of deserts due to drought and land misuse

  • Deforestation

    • Loss of forest biomes

    • Reduced biodiversity and carbon storage

  • Sea-level rise

    • Loss of coastal biomes

Impacts

  • Species displacement

  • Increased competition and extinction

  • Disruption of ecosystem services (water regulation, carbon cycling)