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Patterns of Biodiversity Geographical Gradients & Hotspots

Latitudinal Biodiversity Gradient Terrestrial Vertebrates

Plant Diversity Latitudinal Gradient Marine Bivalve Biodiversity Gradient

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Biodiversity Hotspots

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Major Global Ecosystems

Marine Systems

Marine Biomes Physical

Characteristics

Light Pressure

Temperature Nutrients Salinity

pH – Acidity 2

Major Marine Ecosystems

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Productive marine systems adjacent to areas of highest human densities.

Estuaries

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Estuaries

•  Coastal marine biome that is characterized by mixing of salt and fresh water. – Freshwater inputs from land drainage, streams, and rivers.

Estuaries

•  Coastal marine biome that is characterized by mixing of salt and fresh water. – Freshwater inputs from land drainage, streams, and rivers.

– High variation in salinity.

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Salinity Gradient in Aquatic Systems

Illustration by Peter Summerlin – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php? curid=13274737

Estuaries

•  Coastal marine biome that is characterized by mixing of salt and fresh water. – Freshwater inputs from land drainage, streams, and rivers.

– High variation in salinity. – High level of nutrients inputs.

Estuaries

•  Coastal marine biome that is characterized by mixing of salt and fresh water.

•  Influenced by daily tide cycles.

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Estuaries

•  Coastal marine biome that is characterized by mixing of salt and fresh water.

•  Influenced by daily tide cycles. – Wide daily swings in temperature. – Movement of nutrients out of system.

•  High levels of biodiversity and productivity.

Estuaries

•  Coastal marine biome that is characterized by mixing of salt and fresh water.

•  Influenced by daily tide cycles. •  High levels of biodiversity and productivity. – Important feeding and breeding habitat for many marine and terrestrial species.

Barrier Islands

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Barrier Islands

•  Areas that are net nutrient importers. Often nutrients come from estuaries or mangrove swamps.

•  Sand substrate and creates a rapidly shifting geography.

•  Marine organisms specialized for living in sand.

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Coral Reefs Coral Reefs

•  Ecological Constraints. – Temperature > 20oC (68oF).

20oC Isotherm – Coral Reef Geographical Distribution

Coral Reef Geographical Distribution

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Areas of cold water upwelling limit coral reef distribution. Coral Reefs

•  Ecological Constraints. – Temperature > 20oC (68oF). – Water depth and light penetration.

Coral Reefs

•  Ecological Constraints. •  Dominant Organism is Coral

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Coral Reefs

•  Ecological Constraints. •  Dominant Organism is Coral •  One of the most biologically diverse biomes on earth. – Less than 0.25% of marine systems. – Contain 25% of marine species.

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Mangroves Mangrove Biome

Geographical Distribution

Mangroves

•  Ecology – Coastal marine biome found in areas with relatively low wave energy.

– Dominated by Mangrove Trees •  Low oxygen •  High Salinity •  Water Loss

•  Important feeding and breeding areas for many marine species.

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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.

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