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Topic 5: Land

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  1. 5.1 Soil

    1. 5.1.1Soil as dynamic system

      • Own inputs, outputs, storages, flows within larger ecosystem

    2. 5.1.2Soil composition

      • Inorganic and organic components, water, air

    3. 5.1.3Soil profiles and horizons

      • Soils develop a stable, layered structure known as a profile made up of several horizons, produced by interactions within the system over long periods of time • Soil profiles have distinctive horizons that show a transition from more organic components in the upper surface to inorganic below • 2.5 Application of skills • Sample two soils from the subsoil (B horizon): one from a local garden or field, and one from a natural ecosystem

    4. 5.1.4Soil system inputs

      • Soil system inputs include those from dead organic matter and inorganic minerals • Dead organic matter inputs may include, but not be limited to, plant litter, dead animal biomass, manure • Organic mineral inputs may include weathering, deposition or decomposition, precipitation (water with dissolved minerals), gases, air, humidity and solar energy • In managed soil systems, many inputs are anthropogenic: compost, fertilizer, agrochemicals, irrigation, salinization

    5. 5.1.5Soil system outputs

      • Soil system outputs include losses of dead organic matter due to decomposition, losses of mineral components and loss of energy due to heat loss • Mineral component outputs include wind or water erosion, water and mineral absorption by plant roots, leaching of dissolved plant nutrients and water, diffusion of gases • These outputs can cause the loss or modification of soil components and are different from total loss of soil by erosion; however

    6. 5.1.6Soil transfers

      • Transfers occur across soil horizons, into and out of soils • Include: infiltration, percolation, groundwater flow, biological mixing, aeration, erosion and leaching

    7. 5.1.7Soil transformations

      • Transformations within soils can change the components or the whole soil system • Include: decomposition, weathering, nutrient cycling and salinization

    8. 5.1.8Soil flow diagrams

      • Systems flow diagrams show flows into, out of and within the soil ecosystem • Soil systems are essential for the water, carbon and nitrogen cycles

    9. 5.1.9Soil foundation role

      • Medium for plant growth (seed bank, water store, nutrients) • Stores nitrogen, phosphorus, potassium • Carbon obtained from atmosphere

    10. 5.1.10Soil and biodiversity

      • Provides habitat and niche for many species • Microorganisms, animals, fungi

    11. 5.1.11Soil in element recycling

      • Role in biogeochemical cycles • Detritivores (earthworms) and saprotrophs (fungi, bacteria) decompose matter

    12. 5.1.12Soil texture

      • Physical make-up of mineral soil • Proportions of sand, silt, clay, humus

    13. 5.1.13Texture affects productivity

      • Influences nutrient retention, water retention, drainage, aeration

    14. 5.1.14Soil carbon role

      • Can act as sinks, stores, or sources • Depends on input rate vs. decomposition rate

    15. 5.1.15(HL)—Soil classification

      • By appearance of whole soil profile • Profile diagrams show transfer/transformation processes

    16. 5.1.16(HL)—Soil horizons

      • O: organic layer • A: mixed layer (topsoil) • B: mineral soil • C: parent rock

    17. 5.1.17(HL)—A horizon (topsoil)

      • Rich in organic matter • Most valuable for plant growth • Most vulnerable to erosion and degradation

    18. 5.1.18(HL)—Soil formation factors

      • Climate, organisms, geomorphology (landscape) • Geology (parent material), time

    19. 5.1.19(HL)—Sand, silt, clay differences

      • Particle size and chemical properties • Sand/silt: low cation-exchange capacity (CEC) • Clay: high CEC (increases mineral availability)

    20. 5.1.20(HL)—Soil property analysis

      • Sand/silt/clay percentages, organic matter, water • Infiltration, bulk density, colour, pH

    21. 5.1.21(HL)—Carbon release from soils

      • Released as methane or CO₂ • Causes: global warming, agriculture, wetland drainage • May lead to tipping point

  2. 5.2 Agriculture and food

    1. • 70% ice-free land for agriculture and forestry • Human population increasing, requires feeding

    2. • Needs not accounted for in land-use decisions • Indigenous peoples, low socio-economic groups

    3. • World agriculture produces enough for 8 billion • Not equitably distributed, ~1/3 wasted

    4. • Due to different soils and climates

    5. • Outputs: arable, pastoral, mixed, monoculture, diverse • Reasons: commercial, subsistence, sedentary, nomadic • Inputs: intensive/extensive, irrigated/rain-fed, organic/inorganic

    6. • Nomadic pastoralism, slash-and-burn agriculture • Sustained low-density populations • Less sustainable with modernization and higher density

    7. • High-yielding crops, improved irrigation, synthetic fertilizers, pesticides • Increased food security but criticized for consequences • Fossil-fuel dependent

    8. • Needed in intensive systems for productivity • At expense of sustainability

    9. • A variety of techniques can be used to conserve soil, with widespread environmental, economic and sociocultural benefits • Soil conservation techniques are very varied and can be classified in a number of ways • Conservation from erosion—water and wind a • Water—terracing, contour ploughing, bunding, drainage systems, use of cover crops b

    10. • Humans are omnivorous, and diets include fungi, plants, meat and fish • Diets lower in trophic levels are more sustainable • The yield of food per unit of land area is greater in quantity and lower in cost with crops rather than livestock • Consider: to what extent plant-based diets could make agriculture more sustainable

    11. • Current global strategies to achieve sustainable food supply include reducing demand and food waste, reducing greenhouse gas emissions from food production • Examples include plant-based meat substitutes, reducing nitrogen loss to the atmosphere, low methane rice, reducing methane release by ruminants, extended shelf life for food

    12. • Food security is the physical and economic availability of food, allowing all individuals to get the balanced diet they need for an active and healthy life • Consider: the current extent of food security within differing regions of the world

    13. • Contrasting agricultural choices will often be the result of differences in the local soils and climate • Consider: one pair of contrasting agricultural choices from one biome • Examples: cereal vs. ranching in prairie mollisols; soya beans vs. cattle ranching in tropical forest oxisols

    14. • Soil regeneration, rewilding, permaculture • Non-commercial cropping, zero tillage

    15. • Mixed farming techniques • Improve and diversify productivity

    16. • High-tech greenhouses, vertical farming • Supply food to urban areas • Not always sustainable (fossil fuel dependent)

    17. • Supply chain efficiency, food miles • Farming type and techniques, diet changes • Example: planetary health diet (PHD)

    18. • Traditional methods may be more sustainable • Examples: Brazil nuts, truffles, bamboo, honey

    19. • Evaluate sustainability claims • Must produce enough for global population

    20. • Uneven distribution → malnutrition • Undernourishment and overnourishment • Famine from distribution problems and crop failure