DefinitionCharacteristicsHow much organic material is in itTextureStructureChemical CharacteristicsThe Soil ProfileSoil-forming FactorsGEO 155 1st Edition Lecture 16Last Lecture Vegetation DistributionOutline of Current LectureI. SlidesII. Soilsa. What is Itb. Soil Characteristicsc. Soil Profiled. Soil-forming FactorsCurrent LectureDefinition- Mix of mineral particles and organic materials- Boundary between the solid earth and the atmosphere- Modified by processes reflecting local environmentsCharacteristicsHow much organic material is in itTexture- Size of mineral particlesi. Sand (less than .05 mm)ii. Silt (.002 to .05 mm)iii. Clay (less than .002 mm)iv. Loam – combination of all threeStructure- “peds” – soil clumpsi. Granular – grainyii. Platy – layeredThese 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- Colori. Red – iron oxidesii. Dark brown/black – a lot of organic materialThe Soil Profile- Cross section down through the soil from the ground- Layers – “horizons”1. O Horizon – at the surface, made up of undecomposed plant litter2. A Horizon – just below the surface, made up of humus (decomposed plant litter), dark color, “topsoil”3. E Horizon – lost something (chemical elements, clay particles, etc.)4. B Horizon – gained something5. “C Horizon” – nothing has happened yet, shows what the original material looked like (not technicallysoil yet)- Not every soil has all of the horizons, but must have at least oneSoil-forming Factors1. Climatea. Vegetation (source of organic materialb. Water2. Organismsa. Biocycling – recycling of nutrientsi. Plants – plant to litter to humus to bases cations (either back to plant or lost throughleaching)ii. Animals – mix humus into A Horizon3. Relief – topographya. Water availabilityb.
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