Theme 1 Flashcards
(40 cards)
Define Soil in terms of its composition
Soil is a complex, dynamic mixture of minerals, organic matter, water, air, and living organisms, including:
* Mineral particles
* Organic matter
* Water and air
* Living organisms
Mineral particles are derived from the weathering of rocks, organic matter includes decomposed plant and animal residues, and living organisms contribute to soil fertility and structure.
What are the classifications of soil particles based on size?
Soil particles are classified as:
* Sand (0.05–2 mm)
* Silt (0.002–0.05 mm)
* Clay (<0.002 mm)
Particles smaller than 2 mm are considered soil, while larger particles are part of the parent material.
How does particle size influence soil properties?
Particle size influences:
* Water retention
* Aeration
* Nutrient availability
These factors are critical for soil classification and analysis.
What is chemical weathering?
Chemical weathering is the breakdown of rocks through reactions with water, oxygen, and acids, releasing minerals.
It transforms minerals in the parent material into smaller particles.
What is pedogenesis?
Pedogenesis is the process of soil formation, influenced by factors like climate, organisms, topography, parent material, and time.
It describes how soils develop over time.
What are the approaches to defining soil?
The approaches include:
* Geological approach
* Agricultural approach
* Ecological approach
Each approach emphasizes different aspects of soil.
Define soil according to Certini & Ugolini (2012)
Soil is defined as a centimetric or thicker unconsolidated layer of fine-grained mineral and/or organic material, with or without coarse elements and cemented portions, lying at or near the surface of planets, moons, and asteroids, which shows clear evidence of chemical weathering.
How does soil physically moderate its environment?
Soil moderates its environment by:
* Improving soil structure and aggregation
* Acting as an insulator
* Retaining water and allowing aeration
These functions contribute to environmental stability and support life.
What is the role of soil structure?
Soil structure refers to the arrangement of particles into aggregates, stabilized by organic matter and microbial activity, improving porosity and allowing for water infiltration and gas exchange.
How does soil provide a buffered microenvironment?
Soil acts as an insulator, moderating temperature fluctuations and protecting organisms from extreme conditions and harmful UV radiation.
What is the impact of chemical weathering on soil?
Chemical weathering transforms minerals and releases nutrients like calcium, potassium, and magnesium, driven by water, acids, and organic compounds.
What is the significance of clay minerals and organic matter in soil?
Clay minerals and organic matter have high surface areas and charge properties, enabling them to adsorb and exchange ions, crucial for nutrient cycling and maintaining soil fertility.
What are the primary functions of soil in ecosystems?
Soil plays critical roles such as:
* Habitat for organisms
* Nutrient cycling
* Water regulation
* Carbon storage
* Support for plant growth
These functions are vital for ecosystem health and sustainability.
How does soil regulate water supply and purification?
Soil absorbs and stores water, regulates infiltration and drainage, and acts as a natural filter to remove pollutants and excess nutrients.
What are the characteristics of soil horizons?
Soil horizons have distinct characteristics:
* O Horizon: Organic matter accumulation
* A Horizon: Rich in nutrients
* E Horizon: Light-colored due to leaching
* B Horizon: Accumulation of minerals
* C Horizon: Partially weathered material
* R Horizon: Unweathered bedrock
Each horizon has unique physical, chemical, and biological properties.
Define regolith
Regolith is the layer of loose, unconsolidated material covering bedrock, including soil.
What is eluviation?
Eluviation is the downward movement of dissolved or suspended material within the soil.
What is illuviation?
Illuviation is the accumulation of leached materials in a lower soil horizon.
How does soil contribute to ecosystem services?
Soil contributes to:
* Supporting services
* Regulating services
* Provisioning services
* Cultural services
These services include food production, water purification, and climate regulation.
What are the threats to soil functions?
Threats include:
* Erosion
* Organic matter loss
* Nutrient depletion
* Pollution
Human activities like urbanization, intensive agriculture, and deforestation exacerbate these threats.
What possible impacts does climate change have on soil?
Impacts include:
* Altered weathering rates
* Increased erosion
* Accelerated organic matter decomposition
* Rising soil salinity
These changes affect soil health and its functions.
What is a soil profile?
A soil profile is a vertical section of the soil that exposes its layers (horizons) from the surface down to the parent material.
What is the significance of the A Horizon?
The A Horizon, or topsoil, is rich in organic matter and minerals, critical for plant growth and biological activity.
What processes occur in the E Horizon?
The E Horizon is characterized by the leaching of minerals and organic matter.
