ESS Topic 5.1 Soil (new syllabus)

Soil [5.1.1 SL and HL]

A dynamic system made up of weathered rock particles, organic matter, water, air, and living organisms that forms the outermost layer of Earth's surface. Example: The dark, nutrient-rich soils of the Ukrainian steppes support extensive wheat farming.

Dynamic system [5.1.1 SL and HL]

A complex arrangement of interconnected parts that constantly changes through ongoing processes and interactions. Example: Amazon rainforest soil continuously cycles nutrients through decomposition and plant uptake.

Inputs [5.1.1 SL and HL]

Materials and energy entering a system from external sources. Example: Leaf litter falling from trees adds organic matter to forest soil in temperate deciduous forests.

Outputs [5.1.1 SL and HL]

Materials and energy leaving a system. Example: Nutrients leaching from agricultural soil in monsoon regions of India during heavy rainfall.

Storages [5.1.1 SL and HL]

Accumulated materials or energy held within a system. Example: Carbon stored in peat bogs of Scotland can remain for thousands of years.

Flows [5.1.1 SL and HL]

Movement of materials or energy through a system. Example: Water percolating through sandy soil in the Sahara moves nutrients downward.

Inorganic components [5.1.2 SL and HL]

Non-living mineral particles in soil including sand, silt, and clay. Example: Volcanic soils in Hawaii contain high amounts of basalt-derived minerals.

Organic components [5.1.2 SL and HL]

Living organisms and dead plant/animal matter in soil. Example: Earthworms and decomposing leaves in English garden soil.

Soil profile [5.1.3 SL and HL]

Vertical layers of soil showing different characteristics from surface to bedrock. Example: Prairie soils in North America show distinct dark topsoil over lighter subsoil layers.

Horizons [5.1.3 SL and HL]

Distinct horizontal layers in soil formed through weathering and biological processes. Example: Tropical rainforest soils in Brazil show thin organic horizons due to rapid decomposition.

Soil leaching [5.1.3 SL and HL]

The process where water moving through soil dissolves and carries away soluble substances, like minerals and nutrients, from the upper layers and deposits them in deeper layers or groundwater

Dead organic matter [5.1.4 SL and HL]

Non-living plant and animal remains in various stages of decomposition. Example: Fallen leaves and branches on the floor of Canadian boreal forests.

Inorganic minerals [5.1.4 SL and HL]

Rock fragments and chemical compounds without carbon that provide nutrients. Example: Iron oxides giving red color to Australian outback soils.

Decomposition [5.1.5 SL and HL]

Process where organisms break down dead material into simpler substances. Example: Fungi breaking down fallen logs in Pacific Northwest temperate rainforests.

Mineral components [5.1.5 SL and HL]

Rock-derived particles and dissolved substances in soil. Example: Calcium carbonate in limestone-derived soils of the Yorkshire Dales, England.

Transfers [5.1.6 SL and HL]

Movement of materials from one location to another without chemical change. Example: Clay particles moving from upper to lower soil layers through water flow in monsoon Asia.

Transformations [5.1.7 SL and HL]

Chemical or physical changes converting materials into different forms. Example: Nitrogen compounds changing from ammonia to nitrates through bacterial action in agricultural soils.

Weathering [5.1.7 SL and HL]

Breaking down of rocks into smaller particles through physical and chemical processes. Example: Granite breaking into sand and clay in South African mountain soils.

Nutrient cycling [5.1.7 SL and HL]

Movement and transformation of chemical elements through living and non-living parts of ecosystems. Example: Phosphorus cycling through plants, animals, and soil in Amazon rainforest.

Salinization [5.1.7 SL and HL]

Accumulation of salts in soil, often from irrigation water. Example: Salt buildup in Pakistan's Indus Valley agricultural lands.

Systems flow diagrams [5.1.8 SL and HL]

Visual representations showing movement of materials and energy through interconnected components. Example: Diagram showing carbon movement through vegetation, soil, and atmosphere in a grassland.

Seed bank [5.1.9 SL and HL]

Collection of viable seeds stored naturally in soil. Example: Desert soil in Arizona containing seeds that germinate after rare rainfall.

Essential plant nutrients [5.1.9 SL and HL]

Chemical elements required for plant growth and reproduction. Example: Nitrogen, phosphorus, and potassium (NPK) needed by rice crops in Asian paddies.

Biodiversity [5.1.10 SL and HL]

Variety of living organisms in an ecosystem. Example: Thousands of invertebrate species living in one square meter of temperate forest soil.

Habitat [5.1.10 SL and HL]

Physical environment where organisms live and find necessary resources. Example: Soil providing home for moles, earthworms, and billions of microorganisms.

Niche [5.1.10 SL and HL]

Specific role and resource requirements of a species within an ecosystem. Example: Mycorrhizal fungi living on plant roots, exchanging nutrients for sugars.

Biogeochemical cycles [5.1.11 SL and HL]

Pathways by which chemical elements move through living organisms and physical environment. Example: Carbon moving through atmosphere, plants, soil, and back to atmosphere.

Soil texture [5.1.12 SL and HL]

Physical composition determined by proportions of sand, silt, and clay particles. Example: Sandy soils of coastal dunes drain quickly due to large particle size.

Humus [5.1.12 SL and HL]

Dark, nutrient-rich substance formed from thoroughly decomposed organic matter. Example: Black humus layer in Russian chernozem soils supporting grain production.

Primary productivity [5.1.13 SL and HL]

Rate at which plants produce organic matter through photosynthesis. Example: High productivity in volcanic soils of Java supporting intensive agriculture.

Sand [5.1.13 SL and HL]

Largest soil particles (0.05-2mm) composed mainly of quartz. Example: Beach sand in Caribbean islands providing good drainage but poor nutrient retention.

Silt [5.1.13 SL and HL]

Medium-sized soil particles (0.002-0.05mm) that retain moisture and nutrients. Example: Fertile silt deposits along the Nile River in Egypt.

Clay [5.1.13 SL and HL]

Smallest soil particles (<0.002mm) with high nutrient-holding capacity. Example: Heavy clay soils in English lowlands that become waterlogged in winter.

Carbon sinks [5.1.14 SL and HL]

Reservoirs that absorb and store more carbon than they release. Example: Peat bogs in Ireland storing carbon for thousands of years.

Carbon stores [5.1.14 SL and HL]

Reservoirs holding carbon in equilibrium with inputs and outputs. Example: Mature forests in Pacific Northwest maintaining stable carbon levels.

Carbon sources [5.1.14 SL and HL]

Reservoirs releasing more carbon than they absorb. Example: Thawing permafrost in Siberia releasing stored carbon as methane and CO2.