Soil Formation Factors - Vocabulary Flashcards

Parent material

The five soil-forming factors are: parent material, topography, organisms, climate, and time.
Climate and organisms act on parent material and topography over time.
Parent materials include:
- Primary rocks (Igneous, sedimentary, and metamorphic).
- Sediments from water or wind (e.g., sand and silt).
The type of parent material (inorganic mineral) determines soil properties; for example, if a rock is low in calcium, the soil becomes acidic.
Wind-deposited parent material forms loose sandy soil, and sandy soils are prone to wind erosion.
Carried notes from Lecture 3: Soil formation, morphology, and characteristics.

Topography refers to the shape of the land surface.
It determines water movement and susceptibility to erosion.
Water moves soil particles from up steep hills to low areas or depressions.
Steep land surfaces are susceptible to erosion.
Flat landscapes are frequently waterlogged because water moves slowly.
Topography determines the type of soil formed: upland vs lowland, and steep vs flat land.

Climate influences the rate of weathering of parent material.
Weathering is the breaking down of rocks and minerals by natural forces.
Climatic factors include temperature and water.
Soil temperature determines the rate of chemical reactions and biological processes.
Minerals break down at higher rates in warm temperatures.
High temperature increases evapotranspiration.
Evaporation is the loss of water from soil, and transpiration is the loss of water from plants.
High temperature enhances chemical reactions and increases weathering.
Precipitation (rain, snow, etc.) dissolves minerals that will move by leaching.
In areas with low precipitation, soluble minerals may accumulate in the soil and alter soil properties.
Additional relation: evapotranspiration combines evaporation and transpiration, often noted as
ET = E + T where E is evaporation and T is transpiration.

Include plants, animals, and microorganisms (microbiome) living in the soil.
Microbiome: the microorganism community (including fungi, bacteria, viruses, etc.) living in a specific area (soil, human, or animal body).
Organisms influence the accumulation of organic matter in the soil.
The plant types or vegetation growing in the soil affect the microbiome in the soil.
Examples:
- Bacteria are dominant in prairie vegetation.
- Fungi are dominant in forest vegetation.

Time refers to the time of the soil formation process.
It is the time it takes for climate and vegetation (organisms) to act on the parent material.
It could span from a few years to millions of years, depending on the parent material, climate, and other factors.
By observing the soil horizon, it is possible to tell the time it took to form the soil.
Soils with distinct horizons are older.

The soil formation factors determine the type of soil formed.
The soil-forming processes are mechanisms that act on parent material during soil formation.
They explain how the soil was formed and include physical weathering, chemical weathering, and biological processes.

Chemical weathering changes silicate minerals, containing Si, O, Al, Mg, K, Fe, etc., into soluble and insoluble materials.
The soluble substances form ions that are absorbed by plant roots and used by plants.
The insoluble minerals remain in the soil.
Chemical weathering involves chemical reactions driven by water and air (oxygen).
Water (including acid rain) breaks down minerals into smaller components.
Air oxidizes minerals, causing rusting.
Chemical reactions ultimately create clay minerals and soluble salts.

Involves the accumulation of organic matter during soil formation.
Parent materials are inorganic minerals and do not have organic matter.
Organic matter starts to accumulate as soon as plants begin to grow.
Organic matter is added as fallen leaves and other plant parts.
Animals that feed on plants may die and fall into the soil.
Life-cycle notes for plants:
- The life cycle of plants includes seed germination, vegetative growth, reproduction, and seed production.
- Depending on duration of life cycle, plants are classified as:
- Annuals complete their life cycle in one season: 1 season (not explicitly stated in notes but implied).
- Biennials in 2 seasons (2 years).
- Perennials live for more than 3 years.
Soils dominated by trees have a thin organic layer because it is formed from leaves that have dropped from the trees.
Soils dominated by grasses have a thicker organic layer because the roots are fibrous, have a short life, and contribute to soil organic matter when they die.