Biosphere

• Soil profile

  A cross-section of the different layers (horizons) in the soil
• Soil horizons

  • A0 horizon (organic matter)
  • E horizon (topsoil)
  • B horizon (subsoil)
  • C horizon (parent material/regolith)
• Soil forming factors

  • Climate
  • Vegetation
  • Soil biota
  • Parent material
  • Drainage
  • Relief
• Decomposition

  Breakdown of organic matter and leaf litter by soil biota such as earthworms and microorganisms
• Weathering

  Breakdown of parent material in the C horizon through physical or biological processes
• Leaching


  Downward movement of water and minerals through the soil due to precipitation or snowmelt
• Capillary action


  Upward movement of water and minerals through the soil due to evaporation exceeding precipitation
• Soil types in the UK

  • Brown earth
  • Podzol
  • Gley
• Brown earth


  • Forms in deciduous woodland
  • Thick nutritious leaf litter
  • Biological weathering of parent material
  • Warm and dry climate
  • Limestone or chalk parent material
  • Abundant soil biota
  • Rapid decomposition
  • Well-mixed horizons
• Podzol


  • Forms in coniferous woodland
  • Acidic pine needle litter
  • Slow decomposition
  • Heavy leaching
  • Clear, well-defined horizons
  • Iron pan in B horizon
  • Glacially derived parent material
• Gley


  • Found in tundra areas
  • Cold, wet climate
  • Thin leaf litter layer
  • Waterlogged for most of the year
  • Limited soil biota
  • Distinct, well-defined horizons
  • Impermeable clay parent material