Biogeography Exam 2 - Soils

What are the soil horizons?

O horizon, A horizon, E horizon, B horizon, C horizon, R horizon

Describe the top soil horizon.

O horizon. Mostly derived from organic material, humus.

Describe the second soil horizon.

A horizon. Mixture of humus and clay particles. Is a key link between plants and ground nutrients. Affected by plowing, tilling, etc.

Describe the third soil horizon.

E horizon. Zone of eluviation. Leaching of clays and oxides, carried to lower levels by water flowing through. Coarse sand, silt, and water resistant minerals. Lighter in color.

Describe the fourth soil horizon.

B horizon. Zone of illuviation. Leached material gets deposited. May be reddish or yellowish. Bottom of the solum, the zone of active soil processes. Last layer of true soil.

Describe the fifth soil horizon.

C horizon. Weathered plant material, very hard, cemented soil.

Describe the sixth soil horizon.

R horizon. Lowest zone, loose rock or solid bedrock.

What are the 12 soil orders?

AVAGAMI HOUSE!! Alfisols, Vertisols, Andisols, Gelisols, Aridisols, Mollisols, Inceptisols, Histosols, Oxisols, Ultisols, Spodosols, Entisols

What is an Alfisol?

Occur in moderately weathered forest soils. Gray brown to reddish. Moderate eluviation due to high precipitation. High fertility, high nutrients, typically supplemented with lime or fertilizer, good for farming grains, hay, or dairy farming.

What is an Andisol?

Volcanic in origin. Derived from volcanic ash and glass. High water-holding capacity. Nutrient rich. May cover previous soil horizons. Volcanic tephra weathers into allophane (clay).

What is an Aridisol?

Largest soil class. Desert soils, hot, dry regions. Low organic matter. Little leaching, soil defined by the process of salinization.

What is an Entisol?

Recent, underdeveloped soil. Lacks vertical development/horizons. Worldwide. Due to too much or too little water that prevents the development of these soils. (or slopes)

What is a Gelisol?

Cold and frozen soils underlain by permafrost. High elevation or high latitude. Associated with temps below 0 degrees C. Slow developing and long lasting. Subject to cyroturbation.

What is a Histosol?

Highly organic soil. Peat bogs or marsh habitats. Process of Gleization (buildup of clays).

What is an Inceptisol?

Weakly developed soils. Young but more developed than Entisols. Associated with moist soils and regions. Regarded as eluvial, but no illuvial horizons.

What is a Mollisol?

Grassland soils. Soft, dark, very organic surface layer. High fertility, high nutrients. Soils of the worlds steppes and prairies.

What is an Oxisol?

Tropical soils. Defined by laterization. Typically reddish or yellowish. Nutrient poor due to laterization, low in fertility.

What is a Spodosol?

Northern coniferous forest soils. Northern Hemisphere only (Dfb climates). Soil type is defined by Podzolization. Low fertility and highly acidic. Agriculture is possible with fertilization and management.

What is an Ultisol?

Highly weather forest soils. Reddish in color. High precipitation areas. Result in significant leaching. Less fertile and nutrient rich compared to Alfisols. Good farmland, requires crop rotation and nitrogen fertilization.

What is a Vertisol?

Vertically moving soils. Comprised of expanding clays like montmorillonite. Expands 30% or more when wet. Occurs in subhumid to semiarid regions. Wet/dry action. Clays crack when they are dry allowing bottom material to move to the top. Brown to dark gray. Somewhat nutrient rich.