Major Biomes: Ecosystems of the World

Major Biomes

• A biome is a large, relatively distinct terrestrial region with similar climate, soil, plants, and animals, regardless of where it occurs in the world.

Tundra

• A treeless biome in the far north with harsh, cold winters and extremely short summers.
• Precipitation: 10-25 cm/yr.
• Warmer temperature: short growing season of 50-160 days.
• Frost can occur even in summer.
• Plant diversity is low.
• Low primary productivity.
• Nutrient-poor soils with little organic material.
• Permafrost present.

Boreal Forest or Taiga

• A region of coniferous forests in the northern hemisphere.
• Covers 11% of Earth's land.
• Growing season: a little longer than tundra.
• Precipitation: ~50 cm/yr.
• Soils are acidic and mineral poor.
• Vegetation comprised of drought-resistant conifers.
• Animals: mostly small animals, migrating birds, and some large animals.

Temperate Rainforest

• Coniferous biome with cool weather, dense fog, and high precipitation.
• Located in the Northwest US.
• Precipitation: > 127 cm/yr., heaviest in winter.
• Temperature: winters are mild, summers are cool.
• Soils are nutrient-poor, but high in organic matter.
• Cool temperatures slow decomposition.
• Dominant vegetation: large evergreen trees, old-growth forest.
• Variety of cool climate animal life.
• Very high species richness.

Temperate Deciduous Forest

• Forest biome that occurs in temperate areas with a moderate amount of precipitation.
• Precipitation: 75-150 cm/yr.
• Temperature: seasonality, hot summers, and cold winters.
• Topsoil is rich in organic matter and clay-rich lower layer.
• Vegetation is primarily deciduous.
• Animals: deer, bear, and other small animals.

Temperate Grassland

• Grasslands with hot summers, cold winters, and too little precipitation to support trees.
• Precipitation: 25-75 cm/yr.
• Includes tall grass prairies and short grass prairies.
• 90% of this biome has been lost to farmland.
• Soil has a thick organic matter rich organic horizon.
• Periodic fires keep the dominant vegetation.
• Animals: once covered with bison, smaller animals are still present.

Chaparral

• Biome composed of thickets of drought-adapted evergreen shrubs and small trees, and grasses.
• Mediterranean climate: mild, moist winters, and hot dry summers.
• Soil is thin and often not fertile.
• Vegetation: dense growth of evergreen shrubs with small sclerophyllous leaves.
• Periodic fires are a major factor in plant succession.
• Animals: mule deer, chipmunks, many species of birds.

Desert

• Biome where lack of precipitation limits plant growth.
• Temperature can vary greatly in 24-hr period and yearly.
• Precipitation: < 25 cm/yr.
• Soils are low in nutrients and high in salts.
• Vegetation is sparse.
• Animals are very small to regulate temperature.

Savanna

• Tropical grassland with widely scattered trees.
• Temperature varies little throughout the year.
• Precipitation: 76-150 cm/yr.
• Seasons are regulated by precipitation, not temperature.
• Soil is low in nutrients due to leaching.
• Vegetation: wide expanses of grass, occasional Acacia trees.
• Animals: herds of hoofed animals, large predators (lions, hyenas, etc.).

Tropical Rainforest

• Lush, species-rich biome that occurs where climate is warm and moist throughout the year.
• Precipitation: 200-450 cm/yr.
• Very productive biome.
• Most species-rich biome.
• Occurs in areas with ancient, highly weathered, nutrient-poor soil.
• Nutrients are tied up in vegetation, not soil.
• Forest has three distinct canopy layers.
• Animals: most abundant insect, reptiles, and amphibians on earth.

Human Impacts

• Tropical rainforest destruction.

Freshwater Ecosystems

• Represent 2% of Earth's surface.
• Rivers and Streams: features of a typical river.
• Marshes and Swamps: land that is shallow, fresh water covers for at least part of the year.
• Water-logged soil.
• Water-tolerant vegetation.
• Estuaries: a coastal body of water, partly surrounded by land, with access to the open ocean and a large supply of freshwater from a river.
• Highly variable environment.
• Highly productive.

Marine Ecosystems

• Life zones: intertidal, benthic, and pelagic.
• Intertidal Zone: area between high and low tide marks.
• Benthic Zone: sea floor.
• Pelagic Zone: open ocean.
• Productive Benthic Communities: seagrass beds, kelp forest, and coral reef.

Major Threats to Oceans

• Various threats.

Biodiversity

• The variety of living species on Earth, including plants, animals, bacteria, and fungi.
• Kinds of Diversity: genetic, species, and ecological.
• Benefits of Diversity:
  • Ecological stability.
  • Helps biological communities withstand environmental stress and recover from disturbances.
  • Economic benefits for humans.
  • Provides food and medicines.
  • Provides cultural, ecological, educational, historical, recreational, aesthetic, and scientific value.
• Biodiversity Hotspot: areas with high species richness and high threat levels.

Threats to Biodiversity

• Extinction: mass extinction through history.
• Habitat destruction and fragmentation: example, Cadiz Township in Wisconsin.
• Global climate change.
• Over exploitation: market hunting, medicinal and pet trades, cyanide fishing-tropical fish.
• Pollution: example, Bald eagles and other bird species were decimated by DDT in the 1960s.
• Introduced/Invasive species.
• Disease.

Protection of Biodiversity

• Hunting and fishing laws.
• Endangered Species Act (1973).
• Habitat Conservation Plan (HCP) is a required part of an application for an Incidental Take Permit.