ESS Topic 5: Land - 5.1 Soil

Inputs of soil systems

Water

Organic matter(dead animal biomass)

Air & gases(CO2, O2)

Minerals, Sun(solar(thermal) energy)

Nutrients(compost, Agrochemicals, Guano)

Flows of soil systems

Water(Infiltration, Groundwater flow, Percolation, Erosion) Organic matter(Biological mixing, Decomposition)

Air & gases(Aeration, Erosion)

Minerals(Leaching, Weathering)

Energy(Nutrient cycling)

Output of soil systems

Water(plant uptake, evaporation)

Organic matter(eroded soil)

Air & gases(CO2, O2)

Minerals(wind/water erosion, leaching, diffusion)

Energy(IR, loss of heat energy due to heat loss)

Organic soil components

Living organisms & material from organisms; decay

Inorganic/mineral matter soil components

Obtained from weathering of parental rock; rock fragments, sand, silt, & clay

Soil formation from succession

Weathering of rock & decomposition of organic matter; leaf litter on soil surface is eventually buried below new organic matter layers as leaves fall, manure accumulates, animals die & all are broken down by saprophytes & detritivores

Soil horizons

Distinct layers in soil; Organic layer, Topsoil, Subsoil; upper layer: more organic components

lower layers: more inorganic components(parent material, bedrock)

Soil profile

All the vertical layers of soil horizons

Soil's foundation of terrestrial ecosystems as plant stability

Plants obtain nutrients(N, P, K) with plant roots

Soil's foundation of terrestrial ecosystems as seed bank

Seeds stay inactive until conditions becomes suitable for their growth

Soil's foundation of terrestrial ecosystems as water storage

Soils store water by precipitation, groundwater flow, percolation

Soil's foundation of terrestrial ecosystems as plant nutrients

Plants obtain nutrients from soil by decomposition

Soil's foundation of terrestrial ecosystems as carbon being an exception

Carbon is taken in as CO2 by plant leaves & transformed by photosynthesis

Soil & biodiversity: habitat for many species

≈59% of living organisms live on soil

Microorganisms: N-fixing bacteria

Animals: Earthworms & moles

Fungi

Soils & biodiversity: nieche for many species(Soil food web)

Plant/animal feed on plant dies: energy transferred to soil

Detritivores(millipedes & earthworms): eat decaying leaves & animal remains; transform organic matter into smaller particles(detrititus/leaf litter)

Soils & biodiversity: ideal condition

Loose soil with lots of air spaces; all organisms thrive & soil resilience increased

Soils & recyling of elements: biogeochemical cycles

Major input: dead organic matter from plants

Broken down by detritivores(earthworms) into smaller fragments

Decomposed by saprotrophs(fungi & bacteria)

Soil texture

Physical made-up of mineral soil

Sandy soil texture

Has largest particles; water passes quickly(low water retention)

Low organic matter

High mineral content

Low nutrient(organic) content

High water drainage

Lots of air spaces

Clay soil texture

Has smallest particles; water pass through very slowly(high water retention)

High organic matter

High mineral content

High nutrient(organic) content

Low water drainage

Few air spaces

Silt soil texture

Finely ground particles of parent rock

Medium-low water retention

High organic matter

Low nutrient(organic) content

Medium water drainage

Few air spaces

Soil texture: methodology

Key

Feel test

Mixing with water & layer separation in laboratory

Soil texture & primary productivity: humus

Loose, crumbly texture formed by partial decay of dead plant material

Rich in soil nutrients

Helps water & air retention & prevents waterlogging

Soil texture & primary productivity: adequate water storage

Sandy soils: water pass too quickly; plant roots cannot absorb much

Clay soils: slow water flow; damaged plant roots by high water content

Waterlogged soil: too much water & low productivity

∴Mixture of soil particles have highest primary productivity

Soil texture & primary productivity: high mineral content

Soil containing sand & silt: high in minerals needed for plant growth

Soil texture & primary productivity: ideal soil

Loam soils: most productve as it has a balanced mixture of sand, silt, & clay