1
Q
what are 4 things effected by soils (why study soils)
A
- radiation budget
- water budget
- nutrient cycle
- gas exchange
2
Q
what are the 3 rock types (primary division)
A
- igneous rocks: from molten magma, intrusive (granite) & extrusive (obsidian)
- sedimentary rocks: from other weathered rocks
- metamorphic: from secondary pressure and/or temperature processes
3
Q
what is the chemical composition of the earths crust
A
oxygen, silicon, and aluminum (most important)
calcium, magnesium, and potassium (important for plants)
iron & sodium
4
Q
what are the 3 chemical structures all rocks are formed from
A
acidic, basic, or ultrabasic
5
Q
what are sedimentary rocks and what do they come from
A
particles that have been weathered, eroded, and transported/cemented together (e.g. limestone)
come from weather & erosion of existing rock, accumulation of shells on ocean floor, or accumulation of organic matter of ancient plants
6
Q
what are metamorphic rocks and where do they come from
A
transformation of igneous and sedimentary rocks by heat, pressure, compression, and shear –> example is evaporites
7
Q
what is weathering and the 2 types
A
breakdown of rocks & minerals
1. physical weathering: decrease particle size & increase surface area w physical disintegration
2. chemical weathering: chemical transformation of minerals into new products
8
Q
what are the 4 types of physical weathering
A
- freeze thaw: increase in volume of 9% when water freezes
- thermal changes: from night to day contracting & expanding minerals
- salt weathering: from sea spray evaporating to form salt crystals
- biological weathering: plant roots penetrating rocks
9
Q
what are the 5 types of chemical weathering
A
- direct solutions: cations or anions cause dissolving of soluble salts
- hydration: absorbtion of water
- redox reactions: transfer of electrons –> reduction & oxidization leading to different ions
- hydrolysis: reaction of H* ions with cations in minerals (e.g. acid rain)
- chelation: reaction of elements with complex organic compounds produced from decomposing organic matter –> organic acids
10
Q
what does the rate of weathering depend on
A
strength of rocks: igenous > metamorphic > sedimentary –> acidic more resistant than ultrabasic
intensity of weathering: physical depends on temp, water, bio activity & chemical depends on high temps, biological activity, CO2 and acidity
11
Q
how does climate effect predominant weathering type
A
hotter & wetter climates have more chemical weathering while colder & drier have more physical
12
Q
why did mont royal form
A
because intrusive igneous rock is more resistant to weathering and as earths plates weather away igneous rock pokes up –> will be taller in another 100 million years
13
Q
describe the formation of soils
A
- bedrock exposed to elements starts to disintegrate
- organic materials facilitate disintegration as pioneer plants break down rocks w acids (to get chemical nutrients)
- horizons form: dead organic matter mixed with minerals from weathering create A & C horizons
- developed soils occur as B horizon forms w less soil matter but different mineraology than A and C
14
Q
What are the physical characteristics of soil
A
color, depth, texture, structure, moisture
15
Q
what causes the physical differences in soils (horizons)
A
soil forming processes on underlying parent material –> acts perpendicular to soil surface creating horizons
1. additions: precipitation, organic matter, gas exchange, heat, wind, acid rain
2. transformations: within soil –> decomp of organic matter makes humus and primary minerals create secondary minerals
3. transfers: downward & lateral due to water, while upward due to biological uplift, evaporation, and fluctuating water tables
4. removals: erosion & groundwater takes away ions
16
Q
what are the 6 soil forming factors
A
- parent material: rocks & geological processes
- climate: temperature & precipitation effect soil depth & chemical compositions
- time: older soils more strongly developed, soil formations could be created from long ago conditions
- organisms: ecosystem engineers & vegetation types
- topography: changed movement of water on earths surface
- human activity: climate change, nitrogen in every soil on earth now
17
Q
what are the 3 most important soil properties and what does soil consist of
A
acidity, organic content, texture –> all linked
soil consists of minerals & liquids in porous areas
18
Q
what is soil texture and what is its importance
A
based on particle size –> sand, loam, silt, clay
–> relates to water availability
important for soil infiltration & erosion, controls water availability to plants & provides cation exchange for plant nutrients, also promotes stabilization of soil organic carbon (clay stores large amount of carbon)
19
Q
why is clay especially interesting
A
smallest particles –> layers of thin plates that retain water and ions leading to carbon storage –> 1g of clay can have surface area of 800m2
20
Q
what is soil organic matter
A
found in O horizon & humus in A horizon
made from inputs of dead plant & animal tissues creating outputs through decomposition of organic matter by organisms, drainage, or erosion –> balance between outputs & inputs is how much carbon is stored
21
Q
what are the outputs related to for organic matter
A
rate of decomposition which is controlled by temp & precipitation (higher temp & P = faster decomp) also effected by type of plant tissue (nitrogen and potassium rich decomp faster) & soil properties like fertility, texture, and soil fauna (worms)
22
Q
what are the patterns in the global organic carbon stocks
A
equator systems have high inputs of organic carbon & large outputs due to high temps
temperate systems have low inputs due to lack of vegetation
higher latitude regions (like mtl) have low decomp and accumulation of carbon –> but lose carbon due to agriculture
23
Q
what is the importance of organic matter in soils
A
improves structure & porosity, increases infiltration rate & water availability for plants, supplies nutrients to plants through decomp & cation exchange, stores atmospheric CO2
24
Q
what is soil acidity
A
pH: negative logarithm of H+ ion concentration –> shown on scale where change in pH has big changes in number of H+ ions
25
what is the best pH for agriculture
between 6-7, slightly acidic but close to neutral --> promotes mobilization of phosphorous & cations for plant nutrition
26
what is the global soil pH driven by
climate & chemistry of soil organic carbon/litter input --> why northern latitude systems have low pH & high acidity while arid desert regions have high pH and high alkalinity due to loss of cations and lack of water
27
why is soil pH important
determines nutrient availability, influences cation exchange capacity, controls chemical reactions in soils, influences earth worm activity & other fauna, and has a strong influence on the microbial community in soil
28
what is the CSSC
canadian system of soil classification --> established in 1955 --> 10 soil orders with diagnostic soil horizons
29
what are the 10 soil orders
1. brunisolic
2. cryosolic
3. chernozemic
4. gleysolic
5. lucivsolic
6. organic
7. podzolic
8. regosolic
9. solonetzic
10. vertisol
30
what are the diagnostic soil horizons
3 mineral horizons (A, B, C) followed by suffixes & 4 organic horizons (L, F, H, O) where O is followed by suffixes
31
what are the 4 organic horizons
L: leaf litter
F: partially decomposed leaf & twigs --> folic material
H: humic material
O: from bog or peat vegetation
--> Of: fibrous material w recognizable origin, Om: intermediate/mesic state of decomp, Oh: highly decomp, humic state
32
what are the mineral horizons
A: formed at/near soil surface
B: multiple numbers of B layers sometimes, accumulation from Ae horizon or by alteration of parent material
C: horizon with little evidence of pedogenic activity (doesnt contribute to soil fertility)
R: bedrock & W: water
33
what are brunisol soils
brown soils --> strong Ah horizon, formed under mixed forests, medium fertility, slightly acidic, clay rich --> formed since last glaciation --> 14% surface area
34
what are luvisolic soils
same location as brunisoils but over longer period of time w more rainfall --> rich in base cations, high fertility
--> eluviation (transfer to deeper horizons) of Ae and illuviation (influx from elsewhere) of Bt horizons --> more variation in color than brunisoils with accumulation of clay and aluminium in horizons --> 7% of surface
35
what are podzolic soils
in higher rainfall areas, shaped by vegetation, boreal forests
--> acidic pH promotes Ae horizon of clay minerals & iron oxides --> very distinct horizons from iron & organic matter transport
low to medium fertility because Ae depleted of important cations --> strong leaches
--> 14% of surface (quebec & west coast)
36
what are gleysolic soils
adjacent to water bodies (riparian zones) with shallow water table that creates anoxic conditions reducing iron 3 to iron 2
--> blue grey soil color with mottling and reddish layer from iron transfering illuviation with rising water levels --> 3% of surface
37
what are peat organic soils
formed under waterlogged conditions with slow decomp, accumulation of organic matter & low fertility unless drained --> store huge amount of carbon --> 9% of surface
38
what are regasolic soils
formed on young parent material, in sand dunes in alberta --> no b horizons, 2% of surface
39
what are vertisolic soils
high clay content, in cool subarid grasslands --> little horizon devel, shrinking & swelling leads to huge cracks --> hard for plants to grow & for construction --> 0.3% of surface
40
what are chernozem soils
black earth, for food production, prairies and grasslands --> thick A horizons --> lots of SOM & biomass with dense rooting network --> low leaching of base cations & neutral pH --> very fertile --> salts from top soil can accumulate in C horizon (speckled C horizon) --> 4% of surface (also found in ukraine)
41
what are solonetzic soils
prairie grasslands, accumulate salt at or below surface --> variable fertility and often have too high pH --> need irrigation for agri, 1% of surface
42
what are cryosolic soils
in arctic --> very shallow, weak horizons underlain by permafrost --> 28% of area
43
what are nutrients
elemental requirements of organisms to live
44
what are basic, macro and micro nutrients
basic: nitrogen, hydrogen, oxygen
macronutrients: nitrogen (N), phosphorous (P) potassium (K) --> primary, calcium, magnesium, sulphur --> secondary
micronutrients: small amount needed, iron, maganese, zinc, copper, boron, molybdenum, chlorine
45
what is the issue with micronutrients
too much and its poison, too little and plant is deprives --> not applied to fertilize plants, now seeing deficiencies in areas e.g. zinc deficiency in iran
46
what is nutrient cycling
inputs of nutrients to soil from weathering of minerals from rocks (Ca, Mg, K, P) death of vegetation (N, P), atmospheric deposition (N, Ca, Mg, K), nitrogen fixation from atmosphere
outputs of nutrients through plant uptake/harvest, erosion, leaching, and atmosphere loss (gaseous forms of N)
47
how long does nutrient cycling take
depends on the elements, could be millions of years or just centuries
48
what is nutrient cycling in the ecosystem effected by
1. undisturbed systems: cycling tight when inputs = outputs
2. disturbed systems: cycling loose when outputs > inputs or inputs > outputs (agri systems accumulating fertilizer)
3. ease of loss: N>K>Ca>P
4. retention of nutrients: base cations Ca, Mg, K on cation exchange complex, phosphorous strongly absorbed on clays Fe-AL oxides/hydrooxides and Ca, nitrogen as ammonium form (NH4+) on clays but nitrate form (NO3-) mobile in soils & water
5. importance of soil pH in base cation supply to plants nitrification and P absorbtion --> too acidic Ca & Mg washed away & P trapped by aluminium and iron --> too alkaline P reacts w calcium and becomes unavailable
49
what is nitrogen cycling
1. fixation: incorporate N2 nitrogen gas from atmosphere into usable form by bacteria (to ammonium form) or by fertilizers
2. mineralization: decomposers mineralize N to ammonium form from dead organic matter
3. nitrification: another type of bacteria in oxygen rich soils turn NH4+ ammonium to nitrite (NO2-) and then to nitrate (NO3-) which plant roots prefer
4. dentrification: microbe bacteria in oxygen poor soils turn NO3- to N2 & nitrous oxide (N2O) which goes back to atmosphere --> n2O potent greenhouse gas w 3x warming potential of CO2
5. leaching: loss of NH4+ and NO3- (very mobile in soil) to surface and groundwater
50
how is phosphorous different than nitrogen cycling
P doesnt have gaseous form in almost all enviro systems and is not as redox reactive --> doesnt move through air and not as many transformations, tends to stay put
51
what is the phosphorous cycle
1. inputs: weathering of minerals --> leads to bioavailable phosphate (PO43-) which can attach to cation or organic compounds (3- charge means strong response to positively charged surfaces like clay), dust deposition, decomposition (mineralization)
2. mineralization: decomposing organic matter broken down by endymatic hydrolosis to release inorganic phosphate
3. sorption: P gets chemically attached to soil particles (especially clay & metal oxides) becoming less bioavailable
4. immobilization: uptake of inorganic P into plant roots or by microorganisms, incorporated into organic phosphates (DNA, cell walls, metabolism)
5. solubilization: organic acids from roots disolving soil minerals with phosphorous
6. leaching & output: sandy & over fertilized soils leach phosphate, erosion takes away phosphate molecules, harvest of plants
52
what is the relationship between phosphate availability and soil pH
6-7pH best for agriculture, largest amount of phosphate available, alkaline = less phosphate due to calcium fixation, acidic = less phosphate due to chemical fixation by hydrous oxides of Fe, Al, Mn or reaction with silicate material --> e.g. rainforests have strong weathering, lots of iron & aluminium oxides promoting absorbtion of phosphates so biomass had to adapt to low phosphate
53
what is the potassium cycle
1. input: weathering of minerals, and dust deposition --> only present as K+ (no organic phase & no chemical transformations, no gaseous form & no serious enviro issues)
2. solubilization: dissolution of potassium from soil minerals by water
3. sorbtion: K+ attaches to surface of soils (negative charged organic matter & clay)
4. immobilization: uptake of K+ by plants & microorganisms
5. leaching: loss of soluble K+ to surface and groundwater
54
what are the deficiency symptoms of N, P, & K
P deficient: purple edges of leaves, new leaves still green (global south common)
K deficient: red to yellow edges, begins on lower leaves
N deficient: yellow to red centre, green edges, mobilized & translocates on plant
55
what is the environmental price for the global crop yield
crop yield grown in recent years --> but fertilization process damages enviro --> nitrogen heavily applied in industrialized world, phosphate similar but more in rainforests (due to low pH and lack of available P, plus NA & euro know enviro impacts more) potash is similar distribution to phosphorous
--> see phosphorous imbalance & overfertilization where N & P are transfered through overland flow & N through dentrification (evaporation)
56
what is eutrophication
excess of nutrients in water, causes algae blooms
57
what are dead zones
warming waters w inputs of fertilizer cause algae blooms which die and become oxidized during decomp, depleting water oxygen --> kills animals at top and bottom after dead algae sediments down --> widely distributed especially in industrial world
58
what are cyanotoxins
created by algae blooms, causes closing of beaches
59
what are the solutions to eutrophication
reduce fertilizer, precision agriculture, improved wastewater treatment, ban of phosphates in detergents
nature based solutions: wetland restoration & vegetated riparian buffer strips --> led to decline in 1980s
60
what are soil fauna
macro: mammals, reptiles, insects, earthworms
micro: nematodes, protozoa, rotifers
61
what are soil flora
plant roots, algae, fungi, bacteria
62
what is the global distribution of biomass of soil organisms
tropics: macro
north and south of tropics: meso
poles: micro fauna
63
what are major microorganisms
1. bacteria: common, chemical decomp of org matter, neutral/alkaline enviros, 10to6-9 per g of soil
2. funghi: important to decomp of recalcitrant tissues like wood, same amount per g as bacteria, displace bacteria in acidic poor nutrients
3. protozoa: parasites/predators, important microbial pops, less in soil (10to4 per g)
4. algae: terrestrial & aqautic, important to fix atmospheric N2, close to surface depending on photosynthesis, 10to5 per g
64
what leads to variation in soil bacteria
local conditions, not geographic location --> e.g. well drained soil with neutral pH will have similar bacteria to same soil from different continent
65
what are the ways humans have changed bacteria
addition of new substrates like pollutants alter (dormant bacteria may start to strive)
fertilizers with nitrogen (more than phosphorous due to N gaseous form globally diffusing)
antibiotics: contaminate soil with manure application due to antibiotic in livestock feed --> promotes antibiotic resistance even for human pathogens
66
what are biofilms
rod shaped bacteria interlinked by hairlike structures that form structures communities of biofilms --> important role in nutrient cycling, mitigate excess nutrients in aquatic ecosystems
67
what is the rhizosphere
area of soil where plant roots connect to soil --> root surface physically, chemically, and biologically modifies soil
68
what are mycorrhizal infection of roots
a symbiotic relationship where plants provide fungi with carbs and fungi develop hyphae (lil hairs) which increase surface area to get nutrients and water from soil enviro
69
what are the positive effects of mycorrhiza
increase nutrient uptake by 2-5 fold especially phosphorous, water supply increase, pest control (nematodes), and soil stabilization
70
how do you promote mycorrhiza
organic farming (no pesticides), cultivate crops which develop mycorrhiza (legumes corn potatoes sunflowers) avoid crops that dont (mycor in canola oil and sugar beets --> why canola is an issue), use continous soil coverage (plant after harvest), mild till practices
71
what evolutionary role did mycorrhizal play
global colonization suggest huge evolutionary role during adaptation of plants to terrestrial enviro --> fossils indicate mycorrhizal for over 400 mill years
72
what do earthworms do
ingest & excrete topsoil --> can churn over 15cm of soil evrry 15 years
affect soil structure & nutrient availability --> casts very fertile with N P & cations, also porous helping roots grow & water infiltrate
73
where are earthworms common and not common
temperate pastures common, taiga and some forests (carniforous) low worms, arable soils large range due to fertilizers which hurt their skin
74
what is the effect of earthworms on soil chemistry
enhances exchangeable cations & available phosphorous (good for when P in unavailable in soil), raises pH, large carbon & nitrogen content & higher C:N ratio
75
what is the distribution of earthworms in north america effected by
last maximum glaciation --> usually found south or little bit north of glaciation line --> migrating back up north after being wiped out
76
how are earth worms problematic
mixed forest ecosystems in NA have thick LFH horizons where plants and animals live, earthworms from europe are invasive, migrating much faster and turning over LFH horizons fast leading to soil changes where Ae layer is replaced by Ah, L layer is only LFH left and the pH is higher, bacteria community changed --> they are good for agriculture but bad for animals and habitat
77
what are termites important for
ecosystem engineers effecting biogeochemistry through fertile mounds
78
how do termite mounds form and what do they provide
from collected org matter, nitrogen, and phosphorous growing funghi used to feed offspring --> fertile hotspots promoting water retention --> after abandoned they have high soil fertility with lots of Ca, P, and K and water
79
why are prarie dogs important
keystone species (food for large predators), alter soil enviro through cave and mound systems --> lower pH, improve soil available nitrate, phosphate, and soil organic carbon --> eat digest and excrete soils
80
what is soil erosion
loss of soil from one location to another --> loss of fertile topsoil
81
what are the forms of erosion
1. soil creep: slow downward movement of soil particles, seen in bending trees
2. landslides & earthflows: after massive rainfall events, strength of soil exceeds gravity
3. fluvial erosion: flow of water, most important
4. aeolian erosion: loss by wind, dry windy environments, detachment of particles
82
what are the 3 types of fluvial erosion
1. raindrop impact & splash --> smaller particles displaced by splashing water
2. overland flow: carried away by flow of water
3. deposition: example in chinese loss plateau leading to deposition in yellow river delta in china (new land mass, dynamic system with fertile soils but not sustainable for agri)
83
what are the 3 types of erosion caused by overland flow
1. sheet erosion: entire area equally (biggest global issue), few cm every decade, rocks and vegetation protect surface from impact
2. rill erosion: channels disproportionately effected --> plowing associated
3. gully erosion: extreme form where erosions so strong theres deep crevices --> areas with summer rains --> chinese loss plateau
84
what are the forms of aeolian erosion
1. creeping: large particles blond along land surface
2. saltation: medium particles jumping back onto surface (attrition) loosening smaller particles into the air
3. suspension: air borne particles
--> offsite effect of enhanced deposition
85
what are the problems with measuring soil erosion rates
large temporal/spatial variability (where/when to measure)
labor intensive & costly
dificult to scale up from small plots to drainage basins/landscapes --> little predictive value
86
whats the universal soil loss equation
A = R x K x LS x C x P --> A = erosion rate (tones ha / yr)
87
what does R stand for
rainfall erosivity --> combination of rainfall intensity (overland flow by exceeding infiltration rate) and rainfall energy (ability to splash soil particles downslope & destroy soil aggregates) e.g. north US has less large storms & more snow/drizzle (low energy) and lower precipitation (low intensity)
88
what is K
soil erodibility --> texture is important
89
what is soil erodibility a combination of
1. soil infiltration rate: sand > loam > clay (sand holds more water)
2. ease of detachment of soil particles: silt > clay > sand (not bc of particle size) silt faster detached than clay because clay large charged surface area means particles bind together more forcefully
3. east of transport: clay > silt > sand> gravel --> based on size of particles
90
what has the highest soil erodibility
silt loam at 0.5 due to east of detachment --> wind erosion over eurasian continent deposited lots of silt since last ice age --> plateau in china area now (lots of erosion)
91
what is LS
length and scope of field --> longer slopes accumulate greater overland flow from upslope leading to greater erosion
steeper slopes mean faster overland flow & greater erosion
92
what is C and P
crop type and conservation measures applied --> together since crops are most effective way to deter erosion
93
what crops have least erosion
forest < grass < corn < cotton < bare soil --> foliage protects & holds soil together, O horizon promotes infiltration --> homogenous cropping creates more erosion --> forest with litter and humus has least
94
what are the environmental effects of accelerated erosion on site
1. reduced water availability: increased runoff, remove finer particles (clay org matter) leaving sand and gravel which store less water
2. reduced soil fertility: loss of fertilizers from overland flow, remove smallest particles which have highest nutrient content
3. reduced root depth for plants
4. gullies lead to agricultural land loss
95
what type of feedback loop is erosion
positive: initial increase --> accelerates erosion --> soil surface removed, less water infiltration --> more overland flow, less vegetation, more surface layer removal --> more erosion
96
what are the environmental effects of accelerated erosion off site
1. sedimentation: in river channels, dams, and reservoirs --> 880million tons/yr in US
2. eutrophication: N & P absorbed to eroded soils (particularly clay) get into water bodies --> pesticide transfer, qater quality deterioration & higher water treatment costs (reservoir areas)
3. increased flooding: greater surface runoff & reduced channel volume due to deposited soil
97
what are the strategies to reduce soil erosion rates
1. change crops or planting/harvesting cycles
2. protect soil surface & increase infiltration --> add organic matter (mulching) change tilling practices, contour plowing, wind barriers (shelterbelts)
3. change length & angle of field by terraces or ploughign parallel to slope (east asia)
4. reduce intensity of grazing --> >25% grass cover
98
what was the dust bowl
plains of US & canada in 1930s --> regions lost more than 75% of topsoil due to mismanagement & unusual dry period w strong winds --> onsite effect of loss of fertile soil & offsite effect of depositions of loose particles without soil structure on other fertile areas --> loss of agriculture, food prices skyrocket, poverty & migration occur
99
what are brunisolic diagnostic horizons
Bm --> from minor alteration of mineral horizon from early weathering --> iron oxidization (reddish-brown seen) but minimal clay movement or organic accumulation
100
what are the cryosolic diagnostic horizons
Bg & Cg --> gleyed horizons from oxygen poor saturated conditions reducing Fe3+ to Fe2+ (grey color)
Cy = cryoturbation from frost mixing & Cx = permafrost layer
101
what are chernozemics diagnostic horizons
Ah --> from high organic matter from dense grass rooting system
Cca --> calcic horizon from precipitation evaporation leaving carbonate speckled deposits
102
what are gleysolics diagnostic horizons
Bg & Cg gleyed horizons from prolonged water saturation reducing Fe3+ to Fe2+ producing grey color --> mottling occurs with fluctuating water table reoxidizing Fe locally
103
what are luvisolics diagnostic horizons
Ae --> eluviated horizon thats light grey from Fe/Al leaching downwards with water
Bt --> eluviated horizon enriched with clay
104
what are organic diagnostic horizons
Of --> fibric (recognizable) Om --> mesic intermediate decomp & Oh --> humic --> organic matter accumulating from anoxic saturated or cold conditions
105
what are podzolic diagnostic horizons
Bh from accumulation of humus from leaching of organic acids and Bf from Fe/Al deposits
106
what are regosolic diagnostic horizons
no b horizon --> very young soils with little parent material alteration
107
what are solonetzic diagnostic horizons
Bn --> sodium enriched horizon from salt deposits due to Na+ domination in exchange complex
108
what are vertisolic diagnostic horizons
Bss --> slickenslide from shiny clay content when wet
Bv --> vertically mixed zone due to shrink and swell cracks when clay is wet and dried
109
what is granite made of
intrusive igneous rock made of mica feldspar & quartz --> on surface of canadian shield
geog 203
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