Endangered Biomes Assignment

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Patterns of Biodiversity

Global Ecological Communities and Ecosystems

What is a forest? Why is a forest here?

What determines which plant communities are found where?

A pattern based definition. A Forest is….

•  Species Dominance – Trees. •  Canopy Cover - 10% to 60%. •  Vegetation Height - 4 to 6 feet. •  Extent - 0.4 hectare minimum.

(According to several US Federal Agencies)

A function based definition. A Forest is….

An ecosystem in which trees are the most important organism governing ecological processes.

•  Nutrient Cycling. •  Microclimate regulation. •  Engineer habitat for other organisms. •  Water cycle.

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Why is there a forest here?

Forests are not everywhere.

So, what determines which type of plant communities are found in

an area?

Determinants of Plant Community Composition

•  Climate – Moisture and Temperature.

•  Geology and Soil. •  Disturbance History. •  Biotic Interactions. •  Human Influence.

Source: Botkin and Nesbit Global warming and biodiversity

Growth Response Functions

Low High Average Yearly Temperature

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How do we classify plant communities and ecosystems?

Plant Community Classification

•  be ecologically based. •  be consistent across its geographic extent. •  Be flexible and extensible – Hierarchical.

Source: Whittaker 1975

Whittaker’s classification of Plant Formations

Major Global Ecosystems

Terrestrial Systems

32.5% of Earth’s Surface

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Aquatic

Aquatic Systems

•  Lakes and Ponds. •  Rivers and Streams. •  Wetlands: ecosystems where the plant

composition is effected by the saturation of soil with water. •  Include marshes, bogs, forested wetlands, etc.

Tundra and Alpine

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Tundra and Alpine

•  Plant composition determined by: –  Long season of extreme cold. –  Low availability of water and nutrients. –  Short growing season.

•  Short low lying plants – lichen, mosses, grasses, forbs, and shrubs.

Woodland & Shrubland

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Woodland and Shrub

•  Plant Composition determined by: –  Relative dry and hot climate.

•  Dominated by Shrubs – short woody plants with multiple primary stems.

Shrub Tree

Temperate Grassland

Temperate Grasslands

•  Plant composition determined by: –  Warm and Dry climate. –  Fires maintain system.

•  Dominated by Grasses.

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Boreal Forest

Boreal Forest

•  Plant composition determined by: –  Wet and cold climate. –  Fire maintains system.

•  Dominated by evergreens: Spruce and Fir.

Temperate Forest

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Temperate Forest

•  Plant composition determined by: –  Moderately wet and warm climate. –  System maintained mostly by wind

disturbances. Fire less important. •  Dominated by a mix of evergreen and

deciduous trees.

Cultivated

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Cultivated

•  Plant composition determined by: –  Climate and Soils. –  Human Factors.

•  Dominant plants vary by geography and culture.

Savanna

Savanna

•  Plant composition determined by: –  Shifting extremes of wet and dry seasons.

Climate tends to be warm to hot. –  Fires and grazing important in maintaining

system. •  Dominated by grasses with widely spaced

clumps or individual trees.

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Tropical Forest

Tropical Forest

•  Plant composition determined by: –  Very wet and warm/hot climate. –  System maintained by biotic interactions.

•  Dominated by a very diverse group of large trees.

Desert & Semidesert

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Deserts and Semideserts

•  Plant composition determined by: –  Very dry and warm/hot climate. –  Extreme temperature variation during daily

cycle. •  Dominated by drought resistant plants. The

composition varies with geography and includes cacti, shrubs, and grasses.

Biomes – Major Terrestrial Ecosystems North America

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What is responsible for the geographical pattern of

ecosystems?

Major Global Ecosystems

Terrestrial Systems

and Global Climate

Global Temperature Global Precipitation

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Global Soil Moisture

What determines the pattern of climate globally?

Global Air Circulation Global Air Circulation

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Biomes – Major Terrestrial Ecosystems

Global Terrestrial Ecosystems

•  Location determined by: –  Climate. –  Topography.

•  Species Composition determined by: –  Soil types. –  Evolutionary History. –  Historical Biogeography.