Unit 2: Abiotic Environment (Soils)

Soil

A mixture of inorganic materials (clay, silt, pebbles, sand), decaying organic matter, water, air, and living orgnisms.

Role of Soil

Soil acts as an ecosystem, and a home for plants, animals, and decomposers.

Ecosystems

Nutrient delivery system, recycling system, waste disposal system.

Plants 

Site of germination, support, nutrients, decay.

Animals

Refuge, sewer, or a complete habitat.

Decomposers

Resource

Pedology 

A branch of soil science, focusing on the formation, morphology, and classification of soils as bodies within the natural landscape. 

O-Horizon

Surface Litter: Freshly fallen leaves and organic debris and partially decomposed organic matter.

A-Horizon

Topsoil: Partially decomposed organic matter (humus), living organisms, and some inorganic minerals (humification).

E-Horizon

Zone of Leachings: Area through which dissolved or suspended materials move downward.

B-Horizon

Subsoil: Accumulation or iron, aluminum, and humic compounds, and the clay leached down from the A- and E- horizons.

C-Horizon

Parent Material: Partially broken-down inorganic minerals.

R

Bedrock: Impenetrable layer

What are the 3 Soil Characteristics?

Texture, Porosity, Permeability

Porosity

Number of pores/unit of soil.

Permeability

Determined by the size of pores. 

What do the 3 soil characteristics determine?

Water holding capacity, aeration, susceptibility to erosion, CEC, workability.

How is soil made?

Weathering

Types of Parent Material

Loess, alluvium, lacustrine, till, marine, residual. 

Loess

Transported by wind.

Alluvium

Transported by running water.

Lacustrine

Transported by lace action. 

Till

Transported by glacial ice.

Marine

Transported by oceans

Residual 

Remains in place.

Gleization

Tundra: cold and dry, (prec. > evap.), many small ponds and streams, annual precip: 200-600mm

Podzolization

Coniferous and Deciduous Forests: annual precip.: 650- > 3000

Coniferous Trees

Where summers drier and winter more severe .

Deciduous Trees

Where growing season moist and winter mild. 

Calcification

Grasslands: annual precip.: 300- >1000mm; can experience long lasting droughts; winters cold, summers hot.

Laterization

Tropical Rain Forest: climate is warm and wet year round; annual precip: 2000- >4000; temperate with little monthly variation