4

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)

- 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)

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

o water movement

o cycling of nutrients

o aeration and micro-sites

o movement of bacteria

o 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