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  • Soil is actually very difficult to define. Organic material

Soil Soil Presentation Transcript

  • Soil
  • Soil Composition Water and air content can fluctuate over time.
  • Soil Formation
    • Physical weathering of rocks by wind and water breaks into smaller rocks
    • Biological weathering as lichens break down rocks into mineral particles.
      • Lichens are a mutualistic interaction between a fungus and an algae
      • The fungi secrete an enzyme that breaks down the rock
    Video Link: The Ecosphere: Succession and Soil Formation
  • Primary Succession
      • First plants to grow on bare rock are:
        • lichen
      • Next plants are:
        • mosses
      • followed by:
        • ferns
      • etc., etc. until the climax community is established
  • Where are the animals?
    • The plants attract animals, When the animals die, their bodies decay and add organic material to the soil.
    cc licensed flickr photo by DG Jones:
    • Soil is made up of distinct horizontal layers; these layers are called horizons.
    • They range from rich, organic upper layers (humus and topsoil) to underlying rocky layers ( subsoil, regolith and bedrock).
    Soil Horizons
  • Soil Types
    • Mineral content in soil can be sand (large particles), silt (medium size particles) or clay (small particles).
    • Most soils are made up of a combination of the three.
  • Soil Horizons
    • O Horizon - The top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter).
    • A Horizon - The layer called topsoil ; it is found between the O horizon and the E horizon. Seeds germinate and plant roots grow in this dark-colored layer. It is made up of humus mixed with mineral particles.
    • E Horizon - This eluviation (leaching) layer is light in color; this layer is between the A Horizon and the B Horizon. It is made up mostly of sand and silt. Most of its minerals and clay are lost as water drips through the soil.
  • Soil Horizons
    • B Horizon - Also called the subsoil - this layer is between the E Horizon and the C Horizon. It contains clay and mineral deposits (like iron, aluminum oxides, and calcium carbonate) that it receives from layers above it when mineralized water drips from the soil above.
    • C Horizon - Also called regolith: the layer between the B Horizon and the R Horizon. It consists of slightly broken-up bedrock. Plant roots do not penetrate into this layer; very little organic material is found in this layer.
    • R Horizon - The unweathered rock (bedrock) layer that is beneath all the other layers.