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ESPM 120: REVIEW QUESTIONS FOR FIRST EXAM
Read all the assigned chapters and readings!
Introduction to Soils
• Pedology
• Edaphology
• What are 5 important functions of soils in ecosystems?
• How does soil atmosphere differ from overlying atmosphere (and why?)
• What is soil water holding capacity and how is it commonly reported or measured?
• What group of organisms make soil an important habitat for great biodiversity?
• What are the general outlines of the soil C cycle and its relationship to atmospheric
CO2?
• What is soil profile? Soil horizons?
• General composition of soil volume (solid vs. pore space)
• Characteristics of soil water (total vs. plant available; effect of soil texture)
• Characteristics of soil solids (inorganic vs. organic).
• Components of soil organic matter (humus, microbes, plant parts)
• Sand, silt, clay
• Soil texture
• Soil quality (see book)
• Eugene Hilgard (Mississippi and soils, soil survey, pedology and Berkeley)
• Hans Jenny (soil system, factors of soil formation)
• Peat (formation, location in California and elsewhere, water holding capacity, C/N ratio
and effect on plant N)
• Chilean nitrate (formation as soil layer (Bz horizon); brief overview of soil N cycle; role
of aridity on N accumulation)
Factors of Soil Formation
• Know the “equation” (soils = f (…..))
• Parent materials
- organic vs inorganic
- transported vs. non-transported
- igneous, metamorphic, and sedimentary rocks
- rocks vs. minerals
- primary vs. secondary minerals
- colluvium, alluvium, loess, till, dunes
• Climate
-temperature importance
- rainfall (depth of leaching: water holding capacity + water use)
- importance of water to chemical weathering
• Biota
- plants (role in nutrient cycling; effects of different species)
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- animals (role in mixing)
- gophers and mima mounds
- mima mound formation and type of soil horizons
• Topography
- soil erosion = k x slope
- convex vs. concave landscapes and soil types/processes
• Time
- preCambrian, Paleozoic, Mesozoic, Cenozoic
- Tertiary, Quaternary
- Pleistocene, Holocene, and Anthropocene
- 2 million years
- 10,000 years
• “Sequences” (climosequence, etc + some examples)
Processes of Soil Formation
• the 4 key general processes and examples
• physical vs. chemical weathering
• example of physical weathering
• chemical weathering
- process of hydrolysis
- reactants and products of hydrolysis
- source of acids for hydrolysis
• silicate minerals (primary)
- silica tetrahedron
- classification of silicates based on structure (linkage of tetrahedra)
- temperature of formation vs. structure
- stability in soils vs. structure (and temperature of formation)
- role of acid in breaking down strucuture (H+ exchange for Ca, Na, etc)
• silicate minerals (secondary)
- phyllosilicates
• oxides (secondary)
- Fe and Al oxides
Soil Horizons
• Horizon names correspond to changes relative to parent material
• Master horizons: properties and how they vary from p.m.
• Lower case modifiers: those discussed in class and homework
• Soil horizons vs. soil age (and process/property changes)
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Bulk Density Etc
• Define/understand bulk density, porosity relations
• Calculate amount of some compound in a soil layer using bulk density
• Principle of sedimentation for particle size determination (key factors: grain diameter,
viscosity, etc)
• Archimedes
Soil Architecture
• Soil color
- key factors (organic matter, Fe oxides, water content)
- hue, value, chroma
- value vs. organic matter
- chroma vs. Fe oxides
• Soil texture and particle size
- gravel, sand, silt, clay (size limits)
- textural triangle
- fine earth fraction
- physical and chemical properties of different size fractions (see table in book)
- mineralogy (primary vs. secondary) vs. particle size
• Soil bulk density vs. land use
- compaction
- loss of organic matter
• Soil structure
- the major shapes
- causes of structure (organic matter vs. clay – and shapes controlled by each)
- role of clay minerals in strucuture
o secondary phyllosilicates
o 2:1 (smectite) vs. 1:1 (kaolinite)
o silica tetrahedral layer vs Al octahedral layer
o isomorphous substitution
o net negative charge
o cation exchange capacity (and units)
o base saturation (and the 4 “bases”)
o exchangeable acidity
o Na vs. Ca as exchangeable ions (shells of water)
o Shrink/swell vs. soil structure at different soil depths
o Shrink/swell effects of soil on roads etc
o Dispersion/flocculation (importance of Na)
 Source of Na
 General discussion why it causes dispersion
 Strucuture formed by this process
- importance of structure
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water movement
cycling of nutrients
aeration and micro-sites
movement of bacteria
roots
Soil Classification and Soil Geography
• Soil series
- pedon, polypedon, soil individual
- number in USA
• USDA and soil mapping (Natural Resource Conservation Service)
- 1890’s begin
- 1950’s new soil classification
- first major draft 1975
- “Keys to Soil Taxonomy”
• Data needed to classify soils
- soil moisture regimes
- soil temperature regimes
- surface horizons (epipedons)
- subsurface horizons
• Hierarchy
- order, suborder, great group, sub group, family, series
- formative elements
• Horizons
- Mollic, umbric, ochric, melanic, plaggen/anthropic
- Argillic, nitric, cambic, spodic, albic, duripan, calcic, petrocalcic, gypsic, salic