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esrm 210 - soils > week 1 > Flashcards

week 1 Flashcards

1
Q

5 basic materials of soils

A
  1. mineral solids (45-49%)
  2. organic solids (1-10%)
  3. Air (20-30%)
  4. Water (20-30%)
  5. Organisms (<1%)
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2
Q

porosity

A

total void volume of a soil; remains the same regardless of wetting or drying, or water:air ratio.

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3
Q

mineral solids

A
  • clay: <.002mm
  • silt: .002 - .05mm
  • sand: .05 - 2mm
  • gravel, cobbles, stones: > 2mm
  • Primary minerals: formed by geologic processes, detrital, inherited by the soil
  • Secondary minerals: formed by pedogenic processes, usually clay-sized
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4
Q

organic solids (SOM / OM)

A

Important because:

  1. ​holds water in soil (micropores)
  2. binds soil particels together; aggregates into clumps
  3. nutrient source
  4. energy source for organisms

3 forms:

  1. recognizable detritus from plants/animals on surface or just below
  2. Humus: unrecog. OM; decomp’d and synth’d into brown/black OM
  3. Colloidal OM: small enough to stay suspended in liquid; incl. soluble organics and organic acids
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5
Q

soil water

A

important aspects:

  1. water held by soil is available for uptake by plants/animals
  2. with dissolved elements/compounds make up the
    * *soil solution:** surround roots, interface b/t inorg. particles, OM, and organisms; part of transfer system for nutrients, etc
  3. moves materials through and w/in soil horizons
  4. removes material by leaching
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6
Q

soil air

A
  • higher CO2 than atmos. due to resp of roots/orgs
  • lower O2 than atmos. due to root uptake
  • rel. humidity usally 100% except in very dry desert soils
  • effected by porosity & aeration
  • soil air can be trapped below soil water
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7
Q

soil organisms

A
  • physical breakdown of biotic residues
  • decomp. or org. matter
  • release of
    • exudates to aggregate soil particles
    • acids that weather rock
  • form humus & colloidal org. matter
  • mix soil
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8
Q

4 keys to productivity

A
  • nutrients
  • water
  • oxygen / air
  • anchorage
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9
Q

civilizations dev’d in areas w/ ____ ____, & where they’d be ______, like _____

A
  • rich soils; replenished; deltas
  • Egypt: Nile
  • China: Yellow River
  • Tigris / Euphrates
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10
Q

soils usually rated in terms of ___ ___

A

plant growth

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11
Q

pedological definition of soil

A

soil is a natural body of mineral & organic matter that changes over time in response to environmental factors & biota

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12
Q

soil morphology is…

A

the physical struture of the soil; examined w/ the soil profile

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13
Q

soil horizons are…

A
  • distinct layers formed by pedogenic processes
  • distinct differences in:
    • OM
    • color
    • sand/clay %
    • chemical composition
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14
Q

O horizon

A
  • OM: but can be different types
  • fresh litter & well-decomp’d humus
  • usually above mineral soil (forest)
  • common and very deep in wetlands
  • seldom found in grasslands
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15
Q

A horizon

A
  • surface mineral horizon, darkened by OM
  • may have properties from cultivation
  • usually more fertile
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16
Q

E horizon

A
  • Eluviated mineral hzn where dominant feature is a LOSS of clay, iron, aluminium, OM, etc
  • loss is due to leaching (causing a gray/white color)
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17
Q

B horizon

A
  • mineral hzn w/ either or both:
    • illuvial increase in clay, Fe, Al, OM… from above (E)
    • substantial alteration of original parent material that eliminated rock structure, forms clay or oxides (giving color)
  • orangish, yellowish, greyish
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18
Q

C horizon

A
  • mineral hzn that has little alteration of original PM
  • lacks properties of AEB hzns
  • lies outside of most biological activity
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19
Q

R

A
  • rock material
  • _not_ a horizon
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20
Q

L horizon

A
  • limnic material, uncommon (but occ. in PacNW)
  • lake deposits
  • full of diatoms, clay, OM
  • @ bottom of wetlands
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21
Q

transition hzns

A
  • transition btwn 2 masters
  • dominant hzn listed first:
    • BC: smooth transition w/ B dominant
    • A/B: interfingered w/ A dominant
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22
Q

subordinate O hzn designations

A
  • Oi: little decomp, OM still recognizable
    • i = fibric
  • Oe: intermediate
    • e = hemic
  • Oa: highly decomp’d, OM not recognizable
    • a = sapric = saprophyte
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23
Q

Ap

A

plowed; structural change

24
Q

subord: t

A

accumulation of silicate clays (Bt)

25
Q

subord: k

A

accum. of carbonate (Bk, Ck)

26
Q

subord: s

A
  • accum. of sesquioxides (Fe/Al)
  • orange-reddish color
  • (Bs), illuvial
27
Q

subord: h

A
  • accum. of humified OM (well decomp’d)
  • Bh, Bhs, illuvial
28
Q

subord: g

A
  • gleying, waterlogging, anaerobic, wet soil
  • loss of O2 makes Fe grey/mottled
  • Bg, Cg
29
Q

subord: w

A
  • some development of color/clumps, but not well developed
  • Bw
  • *** B always gets a subord, so Bw if nothing else is special about it
30
Q

subord: b

A
  • buried
  • Ab (an A under other O, A, & B)
31
Q

sources of color

A
  • OM: humus… black/brown
  • Fe oxides: orange/red/yellow
  • carbonates: white
  • bare mixed mineral grains
    • b/w, which eyes avg to grey
    • fresh rocks/minerals
    • waterlogged
    • leached
32
Q

describing color

A
  • hue: basic/primary color
  • value: light/dark
  • chrome: intensity/brightness
  • ex: 10YR 4/4
    • shade 10 of yellow-red
    • value: 4
    • chroma: 4
33
Q

soil texture

A
  • proportion of various size particles < 2mm
  • clay: < .002mm (aka 2 microns)
  • silt: .002 - .05mm
  • sand: .05 - 2mm

[gravel < cobble < stone]

note: texture doesn’t change w/ human impact unless we add or remove soil

34
Q

texture: sand

A
  • rounded, irregular, blocky
  • not plastic or sticky; not moldable
  • larger pores -> water/air can move quickly/easily
  • good aeration
  • usually quartz & other primary minerals
  • can get coated w/ clay, OM, oxides
  • low low nutrition
35
Q

texture: silt

A
  • similar to sand, but smaller, so smaller pores
  • still not very plastic, but OK aeration
  • still low nutrition
36
Q

texture: clay

A
  • usually platey, sometimes rounded
  • plastic, sticky, moldable
  • hold water tightly (b/t plates of clay)
  • made of secondary minerals
  • chemical composition is variable, can be a nutrient src
37
Q

plastic limit

A

% of moisture at which it starts deforming/damaging the soil

38
Q

liquid limit

A

% of moisture at which the truck gets stuck

39
Q

physical props of clay

A
  • shrink/swell
  • cohesion: binds particles -> sharp edges in soil profile
  • soil strength: capacity of a soil to resist stress; influenced by moisture, clay content, OM…
40
Q

soil classes

A
  • sandy > loamy > clayey
  • in the lab: sedimentation, V = kd2
    • ​larger particles fall faster
41
Q

soil structure

A
  • arrangement of soil particles into
  • naturally form in soil
  • can vary by horizon
42
Q

soil structure types

A
  • plate-like: B or C, rocks, sediments
  • prism-like: B, semi-arid -> arid;
    • commonly grasslands; rarely forests
  • block-like: B, forests
  • spheroidal: A, grasslands, fine roots
  • massive: all particles stuck together (w/ binding agent)
  • single-grained: no aggregation, usually sandy soils

*** aggregation is usually a good thing, as it resists erosion

43
Q

promoters of soil structure development (7)

A
  1. climate: wet/dry, freezing/thawing
  2. clays
  3. OM
  4. oxides
  5. plant roots -> exudates -> adhesives
  6. soil organisms (ex: slugs)
  7. salts, carbonates
44
Q

soil depth

A
  • volume of soil available to roots
  • influences growth by affecting nutrition & moisture avalability
  • anchorage / support
  • Effective Rooting Depth
    • depth at which the roots can continue to be active during the entire growing season
    • deeper soils are usually better (> 90% of the time)
      • … but super deep tends to be super old, so likely running out of nutrients
45
Q

soil forming factor fathers

A
  • Dochuchaev: father of pedology -> cropt
  • -> Hans Jenny (sp?): 1st to try to quantify
46
Q

sequences

A

soil formation due to ___ when all other SFFs are held constant

  • climosequence
  • toposequence
  • biosequence
  • (PM-sequence?)
  • chronosequence
47
Q

curve of clay formation rate looks similar to…

A

a weathering curve; that is…

more precipitation = faster clay formation & faster weathering

48
Q

qty of soil OM is highest in…

A
  • temperate regions (& lowest in arctic and tropics)
  • exception: wetlands have high SOM even in Arctic, due to low decomp rates
49
Q

loess

A

a loosely compacted yellowish-gray deposit of windblown sediment of which extensive deposits occur

50
Q

soil association

A
  • group of soils that occur together in a characteristic pattern across a landscape
  • based on parent material + topography
51
Q

SFF: relief/topography

A
  • effects of aspect
    • slope & elevation
    • slope & slope position
  • topo can effect microclimate
    • alter Temp, moisture, rates of change
    • depressions -> water pooling, frost pockets
  • south slope: warmer, drier soil
  • topo changes soil movement, patterns of
    erosion / accumulation
  • topo effect vegetation
    • vally bottom -> riparian: wetter, cooler, more hardwoods, fewer conifers
52
Q

SFF: time

A
  • how long has parent mat. neem exposed to pegoenic processes
    • absolute time vs. relative amount of development
  • glacier bay: 250 years for well-dev’d soil is crazy fast, caused by high amounts of rainfall & salmon spawning
53
Q

SFF: parent material

A
  • rock/mineral material in which soil forms
    • can be OM too!
  • Primary Minerals -> weathering ->
    • altered solids -> more weathering ->
    • ions, soil solution
      • new minerals
  • Secondary Minerals
    • layer silicate clays
    • oxides (esp. Fe & Al)
    • amorphous clay-sized minerals
54
Q

Layer Silicate Clays (secondary minerals)

A
  • tetrahedral sheet
    • O-2, Si+4
  • octahedral sheet
    • O-2 or OH-
    • Al+3, Mg+2, Fe+2, Fe+3
  • expansion properties due primarily to whether or not the clay carries a charge, caused by
  • *isomorphic substitution**
    • ​tetra: Al+3 replaces Si+4
    • octa: Al+3 replaces Mg+2 or Fe+2
  • 1:1 (tetra:octa)
    • Kaolinite: non-exp, 0 charge per unit cell
      • coarse size, low plasticity, low shrink/swell
  • 2:1 (tetra:octa)
    • Vermiculite: exp, -.5 to -.9 charge
      • medium size, medium plast, medium sh/sw
    • Montmorillonite (smectite): very exp, -.4
      • small size, high plast, high sh/sw
  • Muscovite
    • primary mineral (above are all secondary)
    • non-expanding
    • -1 charge
55
Q

cation exchange capacity (CEC)

A
  • clays have a net negative charge
  • cations are used to balance that charge
  • in secondary minerals, cations are not well bonded to the clay, so can exchange w/ each other
  • exchange rxns are how soils store nutrients in a way that plants can access
  • Factors:
    • concentration of ions in solution
    • relative strength of attration of cations
      • Al3+ > (H+) > Ca2+ > Mg2+ > K+ > NH4+ > Na+

esrm 210 - soils (6 decks)

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