IB Environmental systems and societies 5.1 Soil Key Definitions

Aeration is the exchange of gases between soil and the atmosphere.

Biomass is the total mass of living organisms in a given area or volume.

Bioturbation is the mixing and disturbance of soil by living organisms.

Carbon sequestration is the process of capturing atmospheric carbon dioxide (CO₂) and storing it in solid or liquid form.

Cation-exchange capacity (CEC) is the ability of a soil to hold positively charged ions due to negatively charged particles like clays and humus.

Decomposition is the breakdown of organic nitrogen in dead organisms and waste products into ammonium (NH₄⁺).

Denitrification is the conversion of nitrates (NO₃⁻) back into nitrogen gas (N₂), which is released into the atmosphere.

Erosion is the removal of soil particles by wind or water.

Gleying is the formation of waterlogged soils due to prolonged saturation, resulting in greyish or bluish colours.

Humus is a dark, crumbly substance that retains waterand nutrients, improving soil fertility.

Infiltration is the process by which water enters the soil from the surface.

Leaching is the downward movement of dissolved minerals and nutrients through the soil.

Methanotrophs are microorganisms that use methane as a carbon and energy source, reducing methane emissions from soils.

Nitrification is the conversion of ammonia (NH₃) to nitrates (NO₃⁻).

Nutrient cycling is the movement of nutrients like nitrogen, phosphorus, and carbon through the soil, plants, and atmosphere.

Peat is a dense, carbon-rich accumulation of partially decomposed plant material found in waterlogged ecosystems.

Percolation is the downward movement of water through soil layers.

pH measures hydrogen ion concentration, influencing chemical reactions in water.

Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.

A seed bank is a natural store of viable seeds present in the soil, capable of germinating when favorable conditions arise.

Soil is a dynamic system that interacts with the atmosphere, hydrosphere, biosphere, and lithosphere.

A soil catena is a series of distinct but related soils arranged along a slope, formed from the same parent material under varying microclimatic and drainage conditions.

A soil profile is a vertical section of soil that reveals distinct horizons, each formed by long-term interactions of organic and inorganic materials.

Soil texture refers to the relative proportions of sand, silt, clay, and humus in a soil sample.