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  • Insert cover image for Chapter 12 (p. 320).
  • Insert Figure 12.1
  • Insert Figure 12.2
  • Insert Figure 12.3
  • Insert Figure 12.4
  • Insert Figure 12.4
  • Insert Figure 12.5
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  • Insert Figure 12.19 and 12.20
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  • Insert Table 12.1
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  • Insert Figure 12.27 (p. 342)
  • Insert Figure 12.27 (p. 343)
  • Insert Figure 12.28 and 12.29
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12 12 Presentation Transcript

  • Chapter 12: Soils and Soil Development Physical Geography Ninth Edition Robert E. Gabler James. F. Petersen L. Michael Trapasso Dorothy Sack
  • Soils
    • Soil: dynamic natural body capable of supporting a vegetative cover
    • It contains chemical solutions, gases, organic refuse, flora, and fauna
  • Soils
    • Soil integrates:
      • Atmosphere
      • Hydrosphere
      • Lithologic
      • Biotic
    • Soil is home to organisms, forming environments in which they live
  • 12.1 Major Soil Components
    • Four major components of Soil:
      • Inorganic materials
      • Soil water
      • Soil air
      • Organic matter
    • Interaction and proportion of each are important factors
  • 12.1 Major Soil Components
    • Inorganic Materials
      • Insoluble materials
      • Rock fragments and minerals that will not readily dissolve in water
      • Chemical composition of soil result from:
        • Weathering
        • Old deposits
        • Dissolved minerals
      • Soil Fertilization
  • 12.1 Major Soil Components
    • Soil Water
      • Original source is precipitation
      • Open system
      • Capillary water
      • Hygroscopic water
      • Gravitational water
      • Eluviation
      • Illuviation
      • Hardpan
      • Stratification
  • 12.1 Major Soil Components
    • Q: What are some examples of energy and matter that flow into and out of the soil system?
  • 12.1 Major Soil Components
    • Q: How does deposition by capillary water differ from deposition (illuviation) by gravitational water?
  • 12.1 Major Soil Components
    • Soil Air
      • As much as 50% of soil may consist of spaces between soil particles and clumps
      • Supplies microorganisms with oxygen and carbon dioxide
    • Organic Matter
      • Humus: decayed remains of plant and animal material
      • Humus supplies nutrients and minerals to soil
  • 12.2 Characteristics of Soil
    • Readily Testable properties:
      • Color
      • Texture
      • Structure
      • Acidity
      • Alkalinity
      • Capacity to hold and transmit water
  • 12.2 Characteristics of Soil
    • Color
      • Red or yellow (iron)
      • Black (decomposed)
    • Texture
      • Soil texture: particle size
      • Clay (< 0.002 mm)
      • Silty (0.002 to 0.05 mm)
      • Sandy (0.05 to 2.0 mm)
      • Rocks (> 2.0 mm)
  • 12.2 Characteristics of Soil
    • Texture and proportion of particle size
      • Soil grade (% sand, silt, and clay)
      • Loams
      • Soils with a higher proportion of large particles tend to be well aerated and allow for infiltration
  • 12.2 Characteristics of Soil
    • Structure
      • Soil peds
      • Porosity
      • Permeability
      • Classified by form:
        • Columns
        • Prisms
        • Angular blocks
        • Nutlike spheroids
        • Laminated plates
        • Crumbs
        • Granules
  • 12.2 Characteristics of Soil
    • Acidity and Alkalinity
      • pH scale (0-14)
      • Lower pH (higher acidity)
      • Higher pH (alkaline conditions)
      • Soil acidity or alkalinity helps determine available nutrients
  • 12.2 Characteristics of Soil
    • Acidity and Alkalinity
      • Optimum pH varies by plant species
      • Leaching
      • Soils in the east tend to be acidic
      • Soils in the west tend to be alkaline
  • 12.3 Development of Soil Horizons
    • Parent material
    • Soil profiles show:
      • Color
      • Structure
      • Composition
      • Other characteristics with depth
  • 12.3 Development of Soil Horizons
    • Soil Horizons:
      • Distinct layers distinguished by their physical and chemical properties
      • Designated by set of letters that refer to:
        • Composition
        • Dominant process
        • Position in the soil profile
  • 12.3 Development of Soil Horizons
    • Soil Horizons:
      • O horizon
      • A horizon
      • E horizon
      • B horizon
      • C horizon
      • R horizon
  • 12.4 Factors Affecting Soil Formation
    • Weathering
    • Chemical reactions
    • Physical Processes
    • Soil development is a function of:
      • Climate (Cl)
      • Organic matter (O)
      • Relief (R)
      • Parent material (P)
      • Time (T)
  • 12.4 Factors Affecting Soil Formation
    • Parent Material
      • Residual parent material (e.g. physical or chemical breakdown)
      • Transported parent material (e.g. carried by water, wind, etc.)
      • Sandstone
      • Chemicals & nutrients reflect composition
  • 12.4 Factors Affecting Soil Formation
    • Organic Material
      • Plant die and decompose
      • Leaves fall to the ground
      • Most fertile soil are typically grasslands
      • Microorganisms (e.g. bacteria)
      • Earthworms, ants…
  • 12.4 Factors Affecting Soil Formation
    • Climate
      • Global vs. Local scale
      • Equatorial:
        • Higher temps increase soil microorganisms, preclude thick accumulations of humus
      • Middle Latitudes:
        • Cooler temps slow decay and produce rich humus
      • Polar Latitudes
        • Cold temperatures and limited plant growth result in thin humus
  • 12.4 Factors Affecting Soil Formation
    • Climate, Temperature, and organic material
      • Q: What range of mean annual temperature is most favorable for the accumulation of humans?
  • 12.4 Factors Affecting Soil Formation
    • Climate
      • Moisture Conditions
        • Ample precipitation supports plant growth which increases organic content
        • Too much precipitation will cause leaching
      • Evaporation rate
  • 12.4 Factors Affecting Soil Formation
    • Land Surface Configuration
      • Slope
      • Aspect (direction of its faces)
    • Time
      • Young & mature soils
      • Alluvium
  • 12.5 Soil-Forming Regimes
    • Self-forming regimes: vary mainly due to climate and vegetation
    • Climate differences produce 3 primary soil-forming regimes:
      • Laterization
      • Podzolization
      • Calcification
  • 12.5 Soil-Forming Regimes
    • Laterization
      • Humid and subtropical climates
      • Result of high temp and abundant precip.
      • Laterite: soil type (brick-like)
      • No O horizon, absence of organic acids
      • Topsoil reddish
  • 12.5 Soil-Forming Regimes
    • Podzolization
      • High middle latitudes
      • Moist with short, cool summers and severe winters
      • Podzol
      • East Coast of U.S.
  • 12.5 Soil-Forming Regimes
    • Calcification
      • Evapotranspiration exceeds precipitation
      • Often thick calcium carbonate (alkali dusts)
      • Deserts of American west
  • 12.5 Soil-Forming Regimes
    • Regimes of Local Importance
      • Salinization: concentration of salts
      • Occurs most often:
        • in dry areas
        • Intensive irrigation
      • Gleization: poorly drained soils in cold, wet climates
  • 12.6 Soil Classification
    • Soil Taxonomy
      • Soil classification system that is based on their characteristics
      • Natural Resources Conservation Service (NRCS)
      • Mapped by their spatial distribution
    • Soil Surveys
      • Books that outline and describe soils in a region
      • Useful for factors such as fertility, irrigation, & drainage
  • 12.6 Soil Classification
    • NRCS Soil Classification System
      • Based on development and composition
      • Soil order: largest division
      • Subdivisions
      • Horizons below the surface:
        • Subsurface horizon
        • Epipedons
  • 12.6 Soil Classification
    • Common Soil Horizons (NRCS Soil System)
  • 12.6 Soil Classification
    • NRCS Soil Orders: based on a variety of characteristics and processes
  • 12.6 Soil Classification
    • Map of dominant soil orders in U.S.
  • 12.6 Soil Classification
    • World Map of dominant soil orders (NRCS system)
  • 12.6 Soil Classification
    • World Map of dominant soil orders (NRCS system)
  • 12.6 Soil Classification
      • Entisols
      • Inceptisols
      • Histosols
      • Andisols
      • Gelisols
      • Aridisols
  • 12.6 Soil Classification
      • Vertisols
      • Mollisols
      • Alfisols
      • Spodosols
      • Ultisols
      • Oxisols
  • 12.7 Soil as a Critical Natural Resource
    • Soil Fertility
    • Q: What could have been done to prevent the kind of soil loss shown in this example?
    • Q: What other soil conservation practices are often used to preserve the soil resource?
  • Physical Geography End of Chapter 12: Soils and Soil Development