Unit 5: BiosphereMs. Thind

SOIL FORMATION AND SOIL PROFILES

1. Decaying vegetation:In areas of favorable climate for vegetation growth

Decaying organic matter is broken down dark, sticky partly decomposed layer at soil surface humus

Very fertileIdeal for agriculture

FORMATION OF SOIL

2. Leaching: Layer of weathered rock particles and

decaying organic matter allow water to pass through dissolved minerals are carried deep into rock particles

process of water soluble minerals transported through the soil

Tropical wet climate

3. Capillary action: Occurs in dry desert and grassland regions

Surface layers so dry that water is transferred deep in the ground to the surface

Capillary action brings water and dissolved minerals close to the surface

Very fertile

4. TranslocationMovement of solid material from one place to another

Transport of material occurs on the surface or downward through the soil and carried by water

Soil animals play a role eg: worms, burrowing animals

Soil layers or soil profile begin to appear form:

weathering organic debris

parent material

Soil that forms in areas with rainfall and vegetation have distinct soil layers horizons

FORMATION OF A SOIL PROFILE

A-horizon: topsoil layer, darker = more humus = more fertile B- horizon: subsoil, brown/red clay and iron oxide through translocation. In areas of heavy precipitation. Excessive leaching transports soluble materials into bottom layers. C-horizon: rock partially weathered, above parent material or bedrock.

SOIL PROFILE: 3 HORIZONS

5 main soil types:

1. Chernozem soils2. Podzol soils3. Laterite soils4. Sierozem soils5. Tundra soils

SOIL TYPES

Temperate prairie grasslands “breadbasket” areas of the world

North America Prairies, Russian SteppeVery fertile thick, dark humus layerDry summers leaching not a problem

capillary action brings nutrients to the surface

Cold winters freezes soil burrowing animals important to mix up soil

CHERNOZEM SOILS

Topical low pressure beltVery deep and red due to high iron oxide content

Leaf litter adds nutrients to soil Trees have shallow root system to

capture nutrients in top layer Infertile soil

LATERITE SOILS

Coniferous forestsHumid Continental cold winters, warm

summers (due to lack of ocean influence)

Heavily leached and very acidic Thin humus layer of decaying evergreen needles

PODZOL SOILS

Desert soils areas of little precipitation

Limited vegetationOrganic content is lowLittle rainfall = poorly defined soil layers

Can be fertile when irrigated stirring the soil capillary action brings nutrients to surface layer

SIEROZEM SOILS

Permafrost limits the circulation of water in soil = layers not well defined

Low temperatures decomposition of vegetation is slow small decomposing organic layer

TUNDRA SOILS