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Biomes: Global Patterns of Life

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Outline

• Terrestrial Biomes• Marine Ecosystems

Open Ocean Shallow Coasts

• Freshwater Ecosystems Lakes Wetlands

• Human Disturbance

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TERRESTRIAL BIOMES

• Biomes - Areas sharing similar climate, topographic and soil conditions, and roughly comparable communities. Temperature and precipitation are among

the most important determinants in biome distribution.

- Most terrestrial biomes are identified by the dominant plants of their communities.

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Biomes

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Tropical Moist Forests

• Humid tropical regions support one of most complex and biologically rich biomes.

• Ample rainfall and uniform temperatures. Cloud Forests - High mountains where fog

and mist keep vegetation continually wet.

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Tropical Moist Forests

• Tropical Rainforests - More than 200 cm annual rainfall with warm-hot temperatures year-round. 90% nutrients tied up in living organisms. Rapid decomposition and nutrient cycling. Thin soil cannot support continued cropping,

and cannot resist erosion.

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Tropical Rainforests

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Tropical Seasonal Forests

• Semi-evergreen and partly deciduous forests tending toward open woodlands and grassy savannas. Characterized by distinct wet and dry

seasons with hot temperatures year-round

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Tropical Savannas or Grasslands

• Too little rainfall to support forests

• Dry season prone to fire

• Plants with deep, long-lived roots

• Many migratory grazers

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Tropical Savannas or Grasslands

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Deserts

• Characterized by low moisture levels and precipitation that is infrequent and unpredictable from year to year.

• Wide daily and seasonal temperature fluctuations.

• Soils are easily disturbed by human activities, and slow to recover.

• Plants exhibit water conservation characteristics.

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Deserts

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Temperate Grasslands

• Communities of grasses and seasonal herbaceous flowering plants (scattered trees in savannas.)

• Few trees due to inadequate rainfall.• Large daily and seasonal temperature

fluctuations.• Thick organic soils.• Historic grazing by roaming herds of large

ungulates.• Much converted to farmland.

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Grasslands

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Mediterranean

• Characterized by warm, dry summers and cool, moist winters.

• Fires are a major factor in plant succession. Referred to as chaparral in California.

- Biodiversity hotspot. Referred to as thorn scrub in Africa.

- Landscape dominated by acacias and other spiny plants.

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Broad-Leaved Deciduous Forest

• Temperate regions support lush summer plant growth when water is plentiful. Deciduous leaves an adaptation to

freezing temperatures.• Eastern half of US was covered with broad

leaf deciduous forest when European settlers arrived. Much of that was harvested a century ago for timber. Now large areas have re-grown and are

again approaching old-growth status.

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Temperate Deciduous Forests

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Temperate Conifer Forests

• Cone-Bearing• Plants reduce water loss by evolving thin,

needle-like evergreen leaves with thick waxy coating. Can survive harsh winters or extended

droughts and accomplish photosynthesis even under poor conditions.

• Fire often plays role in maintenance.

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Conifer Forests

• Boreal Forest - Northern Conifer Forest Broad band of mixed coniferous and

deciduous trees between 45° and 60° N latitude.

Moist and cool climate with abundant streams and wetlands.

• Taiga - Northernmost edge of boreal forest Species-poor. Harsh climate limits

productivity and resilience.- Produce large peat bogs.

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Boreal Forest

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Conifer Forests

• Temperate Rainforest Wettest portion of coniferous forests of

Pacific Northwest. Mild temperatures, and very abundant

precipitation. (>250 cm)- Canopy condensation is major form of

precipitation.

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Temperate Rainforests

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Tundra

• Treeless• Very short growing season, with cold harsh

winters.• Damage slow to heal.

Arctic Tundra exhibits low productivity, diversity and resilience.

Alpine Tundra receives intense solar radiation, hot daytime summer ground temperatures, and potential droughts.

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Tundra

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MARINE ECOSYSTEMS

• Saltwater ecosystems cover vastly more total area and contain much greater volume of water than all freshwater bodies combined. Oceans hold bulk of world’s water.

• Aquatic ecosystems are influenced by local characteristics of climate, soil, and resident communities, and also by adjacent terrestrial ecosystems.

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Critical Characteristics

• Dissolved Substances• Suspended Matter• Depth• Temperature• Flow Rate• Bottom Characteristics• Internal Convective Currents• Connectivity to Other Aquatic Ecosystems

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Marine Ecosystems

• Vertical stratification is an important aspect of many aquatic ecosystems. Organisms tend to form distinctive vertical

sub-communities.- Benthic - Bottom sub-community.

Low oxygen levels.- Pelagic - Water column

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Light Penetration

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Shallow Coasts

• Coral Reefs - Accumulated calcareous skeletons of colonial organisms (coral). Depth limited by light penetration. Among most endangered communities.

• Mangrove trees grow in salt water. Occur along calm, shallow, tropical coastlines.

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Tidal Environments

• Estuaries - Bays or semi-enclosed bodies of brackish water that form where rivers enter the ocean. Usually carry rich sediments.

- Fan-shaped sediment deposit (delta) formed on shallow continental shelves.

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Barrier Islands

• Barrier Islands - Low, narrow, sandy islands that form offshore from a coastline. Protect inland shores from surf. Prized for human development.

- Loss of vegetation triggers erosion.

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FRESHWATER ECOSYSTEMS

• Lakes Freshwater lakes have distinct vertical

zones.- Epilimnion- Hypolimnion- Benthos

Thermocline - Distinctive temperature transition zone that separates warm upper layer and deeper cold layer.

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Wetlands

• Land surface is saturated or covered with water at least part of the year. Swamps - Wetlands with trees. Marshes - Wetlands without trees. Bogs and Fens - Waterlogged soils that

tend to accumulate peat.• Water usually shallow enough to allow full

sunlight penetration.• Trap and filter water, and store runoff.

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Wetlands

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HUMAN DISTURBANCE

• By some estimates, humans preempt about 40% of net terrestrial primary productivity.

• Temperate broad-leaved deciduous forests are the most completely human-dominated biome. Tundra and Arctic Deserts are the least disturbed.

• About half of all original wetlands in the US have been degraded over the past 250 years.

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Human Disturbance

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Summary

• Terrestrial Biomes• Marine Ecosystems

Open Ocean Shallow Coasts

• Freshwater Ecosystems Lakes Wetlands

• Human Disturbance

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