Chapter 20Terrestrial Biomes

Geosystems 6eAn Introduction to Physical Geography

Robert W. ChristophersonCharles E. Thomsen

Terrestrial Biomes Biogeographic Realms: geographic region where a group of plant and animal species have evolved; generally correspond to continents  There are no rigidly defined boundaries between realms; transition zonesEcotone: boundary transition zone between adjoining ecosystem regions

Biogeographic Realms

Terrestrial Ecosystems: self-sustaining association of land-based plants and animals and their abiotic environment; characterized by specific plant formation classesBiome: large, stable terrestrial ecosystem characterized by specific plant and animal communities  

BiomesUsually named for dominant vegetation

6 broad biomes: forest, savanna, grassland, shrubland, desert, and tundra

These divided into more specific vegetation units

Earth’s Major Terrestrial BiomesEquatorial and Tropical Rain Forest  Tropical Seasonal Forest and Scrub  Tropical Savanna  Midlatitude Broadleaf and Mixed Forest  Needleleaf Forest and Montane Forest  Temperate Rain Forest  Mediterranean Shrubland  Midlatitude Grasslands  Deserts  Arctic and Alpine Tundra 

Figure 20.3

Tropical Savanna

Tropical Savanna ClimatesSouth FloridaInfluenced by ITCZTwo temperature maximumGrasslands with scattered, drought-resistant treesTransitional biome between tropical forests and semiarid regionsSavanna originally covered 40% of land

Tropical Savanna BiomeBetter agricultural soils

Sorghum, wheat, peanuts

Xerophytic plantsSmall, thick leaves; rough bark; waxy or hairy leaf surfaces

Under the influence of the ITCZ for 6 months

Convectional thunderstorms

Semi-permanent high pressure

Serengeti Plains

Sahel Region

Home to large land mammals

Zebras, giraffe, buffalo, elephant, lions, cheetahs, ostrich, crocodile

Figure 20.8

Tropical Savanna Biome

Midlatitude Broadleaf and Mixed ForestSoutheastern US, Atlantic coastal plain, New England, and Great Lakes region

Pines historically dominated the coastal plain

A more even mix of hardwoods and pines occurs farther north and inland

Red fox, white-tailed deer, flying squirrel, possum, bear, cardinal

Broadleaf Mixed Forest

Figure 20.9

Midlatitude Broadleaf and Mixed Forest

Midlatitude Broadleaf and Mixed ForestDeciduous broadleaf trees are common, such as:

Many, many oak species

All hickories

Maples (red and sugar)

Elms

Pines and other conifers are also important.

Poor agricultural soils

Pine plantations

Needleleaf Forest and Montane Forest

In northern North America and northern Eurasia, the closed-canopy version of this forest is called boreal forest.

In the transitional forests in the higher latitudes, the more open version of this forest is called taiga.

This biome is also found in higher elevations and is called montane forest.

Needleleaf Forest and Montane

Forest

Needleleaf Forest and Montane Forest

Consist almost exclusively of needleleaf trees

Pines

Spruces

Firs

Larches

Temperate Rain Forest

Temperate Rain Forest

Dense forests of firs, cedars, hemlocks, and spruces dominate

Persistent moisture, humidity in understory (lots of moss)

In Pacific Northwest, called the coastal evergreen forest

Some of the largest trees in the world exist here

Lower biodiversity than tropical rain forest

Thick undergrowth - ferns

Mediterranean Shrubland

Mediterranean Shrublandaka temperate shrubland, chaparral

Woody shrubs and grassy woodlands

Important for agriculture

Fire adapted speciesDeep rooted with sprouting capabilities

schlerophyllous

Midlatitude Grasslands

Figure 20.15 Figure 20.16

Midlatitude Grasslands

Precipitation great enough to support grasses and some trees, but not forests.

Drought and fire prevent large forests from growing.

Fires are very common in the grassland biome.

Soils found in grasslands are some of the most fertile in the world, though.

Tallgrass and shortgrass prairie in U.S.

The Grassland Biome

DesertsCamel, bighorn sheep, kangaroo rat, scorpion, snakes, and roadrunners

Most animals are nocturnal to avoid high temperatures; cold-blooded animals

Low organic content of the soil; high salt content

Xerophytes

Warm deserts = tropics, subtropics

Cold deserts = midlatitudes

The Desert Biome

DesertificationDesertification: expansion of the desert

Occurs along the margins of semiarid and arid lands

Caused by poor agricultural practices, such as: overgrazing, soil overuse/abuse, improper management of soil moisture, erosion, salinization, deforestation, and climate change.

Arctic and Alpine Tundra

Arctic TundraAssociated with high latitudes

60-80 day growing seasons

No trees, dwarf plants, soggy ground

Low temperatures, precipitation, and evaporation

Poorly developed soils underlain by permafrost

Tundra vegetation: mosses, sedges, snow lichen, arctic meadow grass

Musk ox, caribou, reindeer, weasels, rabbits, polar bears, and mosquitoes

Important breeding ground for migratory birds: geese, swans, waterfowl

Arctic Tundra

Alpine TundraAssociated with high elevations; above timberlineSimilar composition to Arctic TundraNo permafrost, better drainageAndes, White Mts of California, Alps, HimalayasVegetation: grasses, herbs, stunted shrubsMountain goats, bighorn sheep, elk, voles

End of Chapter 20

Geosystems 6eAn Introduction to Physical Geography

Robert W. ChristophersonCharles E. Thomsen