Global Biomes

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What two main climate factors determine biome distribution?

Temperature and precipitation.

What is a biome?

A large ecological region characterized by climate and dominant vegetation.

What is physiognomy?

The outward appearance or physical structure of vegetation.

What are ecological equivalents?

Vegetation formations with similar structures but different species in geographically separated regions.

What is the treeline?

The boundary beyond which environmental conditions are too harsh for trees to grow.

What are the eight major terrestrial biomes in the lecture?

Tundra, taiga, temperate conifer forests, temperate deciduous forests, tropical dry forests, tropical rain forests, deserts, and grasslands.

What climate characterizes tundra?

Extremely cold temperatures and a very short growing season.

What vegetation dominates the taiga?

Needle-leaved evergreen conifers.

How do conifers benefit from the short growing season?

They can take advantage of the short growing season without regrowing all their leaves annually.

What is the main climate challenge for temperate deciduous forests?

Seasonal cold and freezing temperatures.

Why do deciduous trees shed their leaves?

To survive the unfavorable cold season.

What is a tropical dry forest?

A tropical forest with a pronounced dry season.

What does drought deciduous mean?

Plants shed their leaves during dry periods to reduce water loss.

What causes seasonal precipitation patterns in tropical dry forests?

The seasonal migration of the Intertropical Convergence Zone (ITCZ).

What is the ITCZ?

A region of converging air near the equator associated with rising air and precipitation.

What climate characterizes tropical rain forests?

Warm temperatures and substantial precipitation throughout the year.

What are the major vertical layers of a tropical rain forest?

Emergent trees, upper canopy, lower canopy, understory, and ground cover.

What are root buttresses?

Large supporting extensions at the bases of tree trunks.

What is a temperate rain forest example from the lecture?

The Hoh River Valley in Washington.

What characterizes a desert biome?

Very low precipitation and limited water availability.

Why are many deserts located near 30° north and south latitude?

Descending air in subtropical high-pressure belts suppresses cloud formation and precipitation.

What is the Humboldt Current?

An ocean current that helps supply fog moisture along the west coast of South America.

How does the Humboldt Current support life in the Atacama Desert?

It supplies moisture as fog where rainfall is extremely rare.

What is a rain shadow?

A dry region on the leeward side of mountains where descending air produces limited precipitation.

How do saguaro cacti store water?

In their column-like stems, which swell after rainfall.

What are cactus spines, botanically?

Modified leaves.

What is a grassland biome?

A biome dominated by grasses rather than a closed forest canopy.

How do grasses benefit from belowground growth?

It reduces exposure to stress and allows recovery after disturbance.

Why can wildfire help maintain grasslands?

Fire can limit tree establishment or survival.

What is the general moisture gradient across North American grasslands?

Conditions are generally drier in the western shortgrass prairie and wetter toward eastern grasslands.

Why is western shortgrass prairie relatively dry?

It is affected by a rain shadow created by the Rocky Mountains.

Where does moisture for eastern North American grasslands come from?

Circulation patterns bring moisture northward from the Gulf of Mexico.

What two factors influence the prairie–forest boundary?

Climate and disturbances such as wildfire.

How does temperature generally change from the equator toward the poles?

It generally decreases.

What does a climate graph show?

Monthly temperature and precipitation patterns.

How is temperature typically represented on a climate graph?

By a line showing monthly temperatures.

How is precipitation typically represented on a climate graph?

By bars showing monthly precipitation.

How can you distinguish tropical rain forests from tropical dry forests using climate data?

Rain forests receive substantial rainfall throughout the year; dry forests have a pronounced dry season.

How can you distinguish tundra from taiga by vegetation?

Tundra has little or no tree growth, while taiga is dominated by conifers.

How can you distinguish deserts from grasslands?

Deserts have very low precipitation and sparse vegetation; grasslands support extensive grass cover.

How can you identify a temperate deciduous forest from its seasonal pattern?

It has seasonal temperatures and trees that shed broad leaves during the cold season.

What determines the transition from tropical vegetation to temperate forests?

Changes in latitude and temperature, especially the increasing likelihood of freezing.

Why can similar vegetation structures occur in different parts of the world?

Similar environmental conditions can favor similar plant structures even when species differ.