Life on Land - Chapter 2

Life on Land - Chapter 2

• A biome is a large, distinct terrestrial region.
• Biomes have similar climates, soil, plants, and animals.
• Biomes are primarily distinguished by their dominant plants and associated climates.
• Examples of terrestrial biomes include grassland, desert, tropical rainforest, deciduous forests, coniferous forests, and tundra.
• Freshwater and marine are the two basic aquatic biomes.

Terrestrial Biomes Examples

• Grassland: Characterized by abundant grass.
• Desert: Characterized by scarce water; often hot and dry.
• Tropical Rainforest: Warm temperatures and high rainfall.
• Deciduous Forest: Trees lose their leaves seasonally.
• Coniferous Forest: Trees have needle-like leaves.
• Tundra: Treeless biome, cold and dry.

Geographic and Seasonal Variations

• Temperature and precipitation significantly affect biome types.
• The graph illustrates the relationship between average temperature, precipitation and the distribution of various biomes.

Biome Distribution on Earth

• A diagram displays the distribution of biomes across the globe in relation to temperature and precipitation.

Climate Factors

• The Earth's spherical shape and tilt cause uneven heating, leading to different climate patterns.
• Patterns in which air circulates produce major differences in rainfall.
• Near the equator, warm, moist air rises. Then cools, condenses, and falls as rain.
• Warmer dry air falls back to surface leading to deserts.
• Rainfall tends to be concentrated near the equator.
• Continents experience a change in the weather depending on the time of year.

Weather vs. Climate

• Weather describes atmospheric conditions at a specific time and place.
• Climate is the long-term average of weather patterns.
• Oceans are important in influencing weather and climate patterns.
• Earth's climate involves interactions of various spheres (atmosphere, hydrosphere, geosphere/lithosphere, cryosphere).
• The biosphere consists of all four.

Coriolis Effect

• The Earth's rotation affects wind patterns by causing apparent deflections (clockwise in the Northern Hemisphere, counter-clockwise in the Southern Hemisphere).

Soil: Foundation of Terrestrial Biomes

• Soil is a complex mixture of living and non-living material.
• Soil is categorized based on vertical layering (soil horizons).
• Soil profiles provide snapshots of soil structure, which are constantly changing.

Soil Profile

• The soil profile is a vertical section of soil from the ground surface down to the underlying rock.
• The figure shows layers (horizons) within soil.
• O horizon: organic matter (humus).
• A horizon: top soil, rich in organic matter, typically dark.
• B horizon: subsoil, zone of accumulation of leached materials; often contains minerals such as calcite in arid climates (caliche).
• C horizon: weathered bedrock, below soil profile.

Soil Orders

• There are 12 orders of soil.
• Specific soil orders like Entisol, Mollisol, Alfisol, Andisol, Aridisol, Inceptisol, Histosol, Oxisol, Vertisol, Spodosol, Ultisol, and Gelisol are listed.

Soil Characteristics

• Specific soil descriptions were provided for different soil orders (like Ultisol and Aridisol)
• Ultisol (also known as laterization) is highly leached.
• Aridisol (found in deserts) is low in organic matter and prone to salinization

Tropical Rainforests

• Little temperature variation throughout the year.
• High daily rainfall.
• Found near the equator in specific regions.
• These soils are nutrient-poor and acidic.
• Most plants have shallow roots.
• Nutrients are tied up in vegetation rather than soil.
• Characterized by three distinct canopy layers.

Tropical Savanna

• Occurs north and south of tropical dry forests, within 10-20 degrees of the equator.
• The climate alternates between wet and dry seasons.
• Drought-associated wildfires can happen.
• Soils are low in nutrients due to leaching.
• Wide expanses of grass and occasional acacia trees.
• Vegetation has fire-adaptive characteristics.

Deserts

• Major bands at 20-25 degrees N and S latitude.
• Found on every continent.
• Water loss through evapotranspiration often exceeds precipitation.
• The driest biome on Earth.
• Soil usually has extremely low organic matter, especially humus.
• Plant cover can range from sparse to absent.
• Abundant animal biodiversity, but low animal density.
• Diverse animal adaptations to conserve water.
• Desert plants have adapted with spines, thick cuticle, deep roots, and succulents.

Mediterranean Woodland and Shrubland

• Occurs on all continents except Antarctica.
• Climate is cool and moist during fall, winter, and spring, but hot and dry in summer.
• Soils are fragile but with moderate fertility.
• Trees and shrubs are typically evergreen.
• Plants have adaptations for fire.
• Humans have greatly impacted the land.

Temperate Grassland

• Extremely widespread distribution.
• Annual rainfall 300-1,000 mm.
• Experience periodic droughts.
• Soils are extremely nutrient-rich and deep.
• Dominated by herbaceous vegetation.
• Large roaming ungulates (like bison and cattle).

Temperate Forests

• Characterized by four seasons.
• Rainfall averages 650-3,000 mm.
• Dominated by deciduous trees.
• Rich in nutrients and deep fertile soil.

Boreal Forests

• Confined to the Northern Hemisphere.
• Covers 11% of Earth’s land area.
• Thin, acidic soils that have low fertility.
• Dominated by evergreen conifers.
• High animal density (like deserts).
• Historically low human intrusion.

Tundra

• Covers most lands north of the Arctic Circle.
• Cool and dry climate with short summers.
• 200-600 mm precipitation.
• Low decomposition and primary production rates (like deserts).
• High diversity of native mammals.
• Temperature rarely higher than 10°C; short growing season (50 to 160 days).
• Nutrient-poor, acidic soils with little organic matter.
• Low primary productivity and decomposition.

Mountains

• Formed by geological processes; concentrated in belts of geological activity.
• Climate changes with elevation (altitude) and latitude.
• Soils are generally well-drained and thin.
• Flora and fauna change with elevation.
• Historically used for resources for people.