GEO 155 1st Edition Lecture 16 Last Lecture Vegetation Distribution Outline of Current Lecture I Slides II Soils a What is It b Soil Characteristics c Soil Profile d Soil forming Factors Current Lecture Definition Mix of mineral particles and organic materials Boundary between the solid earth and the atmosphere Modified by processes reflecting local environments Characteristics How much organic material is in it Texture Size of mineral particles i Sand less than 05 mm ii Silt 002 to 05 mm iii Clay less than 002 mm iv Loam combination of all three Structure peds soil clumps i Granular grainy ii Platy layered These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute iii Blocky Chemical Characteristics Base Cations Calcium ions Potassium ions Magnesium ions More basic higher pH Or Hydrogen ions More concentration of hydrogen ions lower pH more acidic Color i Red iron oxides ii Dark brown black a lot of organic material The Soil Profile 1 2 3 4 5 Cross section down through the soil from the ground Layers horizons O Horizon at the surface made up of undecomposed plant litter A Horizon just below the surface made up of humus decomposed plant litter dark color topsoil E Horizon lost something chemical elements clay particles etc B Horizon gained something C Horizon nothing has happened yet shows what the original material looked like not technically soil yet Not every soil has all of the horizons but must have at least one Soil forming Factors 1 Climate a Vegetation source of organic material b Water 2 Organisms a Biocycling recycling of nutrients i Plants plant to litter to humus to bases cations either back to plant or lost through leaching ii Animals mix humus into A Horizon 3 Relief topography a Water availability b Erosion
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