Soil

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  • Soil is actually very difficult to define. Organic material
  • Soil

    1. 1. Soil
    2. 2. Soil Composition Water and air content can fluctuate over time.
    3. 3. Soil Formation <ul><li>Physical weathering of rocks by wind and water breaks into smaller rocks </li></ul><ul><li>Biological weathering as lichens break down rocks into mineral particles. </li></ul><ul><ul><li>Lichens are a mutualistic interaction between a fungus and an algae </li></ul></ul><ul><ul><li>The fungi secrete an enzyme that breaks down the rock </li></ul></ul>Video Link: The Ecosphere: Succession and Soil Formation
    4. 4. Primary Succession <ul><ul><li>First plants to grow on bare rock are: </li></ul></ul><ul><ul><ul><li>lichen </li></ul></ul></ul><ul><ul><li>Next plants are: </li></ul></ul><ul><ul><ul><li>mosses </li></ul></ul></ul><ul><ul><li>followed by: </li></ul></ul><ul><ul><ul><li>ferns </li></ul></ul></ul><ul><ul><li>etc., etc. until the climax community is established </li></ul></ul>
    5. 5. Where are the animals? <ul><li>The plants attract animals, When the animals die, their bodies decay and add organic material to the soil. </li></ul>cc licensed flickr photo by DG Jones: http://flickr.com/photos/dgjones/2151134648/
    6. 7. <ul><li>Soil is made up of distinct horizontal layers; these layers are called horizons. </li></ul><ul><li>They range from rich, organic upper layers (humus and topsoil) to underlying rocky layers ( subsoil, regolith and bedrock). </li></ul>Soil Horizons
    7. 8. Soil Types <ul><li>Mineral content in soil can be sand (large particles), silt (medium size particles) or clay (small particles). </li></ul><ul><li>Most soils are made up of a combination of the three. </li></ul>
    8. 9. Soil Horizons <ul><li>O Horizon - The top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter). </li></ul><ul><li>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. </li></ul><ul><li>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. </li></ul>
    9. 10. Soil Horizons <ul><li>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. </li></ul><ul><li>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. </li></ul><ul><li>R Horizon - The unweathered rock (bedrock) layer that is beneath all the other layers. </li></ul>

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