Midterm 2 Flashcards
(106 cards)
1
Q
In what ways are soils important in other spheres? (4)
A
- Energy budget
- Hydrology (percolation and evapotranspiration)
- Nutrient movement
- Carbon cycle
2
Q
Summarize the geologic cycle
A
- Magma is in the asthenosphere
- Magma can either build crust or reach surface and cool
- Tectonic plates are responsible for movement of magma, and heat and pressure that transforms rocks
- Rocks are formed by cooling magma
- Can then be transformed in many ways
3
Q
Define the three types of rocks
A
Igneous: composed of minerals formed from molten magma
Sedimentary: composed of minerals weathered from other rocks
Metamorphic: formed from secondary pressure/temperature processes
4
Q
What are the two classifications of igneous rocks?
A
Intrusive: these cool in Earth’s surface
Extrusive: these cool outside
5
Q
Describe the differences in intrusive and extrusive igneous rocks and give examples
A
Intrusive develop larger grain sizes because these cool slower (granite, diorite)
Extrusive cool much faster (obsidian, pumice, basalt
6
Q
Describe general patterns of rock types across Canada
A
Much of eastern & parts of Northern Canada is covered by the Canadian shield, which is mostly igneous rock
Prairies towards the west are generally sedimentary
7
Q
What crystals is granite made of?
A
Feldspar, quartz, mica
8
Q
Define mineral. How are they formed, and where can you find them?
A
- inorganic natural solid compound with specific chemical formula and crystalline structure
- formed at high temperature and pressures in crust
- in igneous and metamorphic rock
9
Q
Describe the structure of a mineral tetrahedral
A
[SiO4]4-
- silicon surrounded by 4 oxygen with negative charge
10
Q
List and describe the different mineral formations. (5)
A
Olivine - island, tetrahedrals form clusters (no Si-O-Si), bond w Fe/Mg
Pyroxene - chain, 2 shared, and 2 unshared oxygens (50%)
Amphibol - double chain, some share 2 O and some 3 (62.5%)
Mica - sheet, sequences of chains where 3 O share (75%)
Quartz - 3D structure, 100% Si-O-Si
11
Q
What is an isomorphous substitution?
A
replacement of central Si with Al (has different valence)
results in aluminosilicate minerals
now must incorporate a cation
12
Q
Examples of feldspars (3)
A
Albite - Na addition
Anorthite - Ca addition
Orthoclase - K addition
13
Q
Give an example of an acidic rock, a basic rock, and an ultrabasic rock.
A
Acidic - granite, rhyolite
Basic - gabbro, basalt
Ultrabasic - peridotite
14
Q
Describe the bond strengths in different element-O bonds
A
From strongest to weakest, and most resistant to easily weathered
- Si-O-Si
Al-O-Al
Fe/Mg-O
Na/K/Ca-O
15
Q
Define and describe felsic and mafic rocks.
A
Felsic - high in silica, light, lower melting point, highly resistant to weathering, generally contain potassium and sodium, more quartz and feldspar
Mafic - mostly magnesium and iron, darker, high melting temp, low weathering resistance, more pyroxene and olivine
16
Q
Define sedimentary rocks.
A
Particles that have been weathered, eroded, and transported and cemented together
17
Q
What are the 4 processes/sources of sedimentary rocks?
A
Weathering and erosion of existing rocks (sandstone)
Accumulation of shells on ocean floor (limestone)
Accumulation of organic matter of ancient plants (coal)
Precipitation of secondary minerals (CaCO3)
18
Q
What are the 5 stages of sedimentary rock formation?
A
Weathering - generation of particles
Erosion - removal of particles from parent material
Transport - dispersal of particles and ions
Deposition - settling out of transporting fluid
Lithification - transformation into solid rock
19
Q
What are the 6 clast sizes?
A
> 80 mm - boulders and cobbles - conglomerate (breccia)
2mm - pebbles and gravel - conglomerate
0.5-2mm - sand, sandstone
0.062-0.5mm - sand, sandstone
0.0039-0.062mm - silt, siltsone
<0.0039 - clay, shale
20
Q
Describe chemical sedimentary rocks and give 5 types.
A
new minerals formed in situ
Limestone CaMg(CO3)2
Evaporites - Na and Ca chlorides and sulphates
Ironstone - oxides and hydroxides of Fe and Al
Hydrothermal deposits (black smokers)
Organic - coal, oil
21
Q
What are metamorphic rocks? How are they formed?
A
rocks created by transformation of igneous and sedimentary rocks
- Heating
- Pressure
- Heating + pressure
- Compression and shear
usually harder and more resistant to erosion than parent
22
Q
What is weathering and what are the two main types?
A
Breakdown of rocks and minerals
Physical - physical disintegration of rocks and minerals, decreasing particle size and increasing surface area
Chemical - transformation of minerals into new products
23
Q
4 types of physical weathering
A
Freeze thaw
Thermal changes
Salt weathering
Biological
24
Q
Chemical Weathering (6)
A
Direct solution - dissolution of soluble salts
Ex. Na and K, Cl and SO4
Hydration - Minerals absorbs water, then mineral disintegrates & forms new mineral
Ex. hematite to limonite or anhydrite to gypsum
Redox reactions - change in element valency
Ex, iron, Fe2+ <-> Fe3+
Chelation - reaction of normally insoluble elements (ex. Fe, Al) with complex organic compounds produced by decomp of organic matter
Carbonation - reaction of carbonic acid H2CO3 with carbonates
H2CO3 produced by dissolution of CO2
Results in soluble product
Hydrolysis - reaction of H+ ion with cations in minerals
Very important process
We see lots with acidic rain
H+ from CO2 dissolution in water or from acid rain
25
What impacts the rates of weathering?
- intensity of weathering processes and strength and resistance of minerals
- strength -> igneous > meta >sed
26
How does weathering intensity change?
Physical facilitated by freeze thaw cycles, variations in water content, temp, and biological activity
Chemical weathering facilitated by high temperatures and high biological activity, production of organic acids and CO2 in soil, and acidity (ex. Acid rain)
27
Explain the weathering climate diagram
- strong chemical if high rain and high temp
- strong physical if slightly drier and cold
- moderate chemical if mid both
more physical towards cold and dry and more chemical towards hotter and wetter
28
How were monteregian mountains formed?
Magma that never reached surface, was covered by sediment, then this was uncovered and eroded and is now igneous mountains
29
How are soils formed?
Bedrock disintegrated by physical processes
Becomes parent material
Organic materials come in and advance soil formation (chemical weathering)
Organic matter begins to accumulate, eventually see horizons
horizons continue to develop
30
Describe the typical soil profile
O horizon on top - only organic matter
A horizon - mix organic and minerals, very dark
E - transition between A and B - pale
B subsoil, brown
31
What are the 4 soil forming processes?
transformations - organic matter to humus, primary minerals turning to compounds
transfers - up and down, humus clay ions out, ions in
- caused by capillary rise
removal - leaching and erosion
additions - precipitation, ions, organic matter
32
5 soil forming factors
parent material (sediment type, minerology, ease of weathering)
climate (temp, precip)
time (older soils more developed)
organisms (habitat type and vegetation)
topography (controls water regime and rates of soil erosion)
- humans also important
33
How does climate effect soil formation?
- high temps and high precip, horizons deeper
savanna shallow
polar desert little chemical alteration and soil shallow
34
Describe differences in profiles for prairie vs forest
Prairie - thick A horizon, both A1 and A2, has Ck layer
Forest - thin A horizon, E horizon present
35
How does topography control soil moisture regimes?
top of slope - free drainage
middle of slope - restricted drainage
bottom - poor
36
Describe soil texture
defined as mixture of gravel, sand, silt, and clay particles
37
what is the importance of soil texture
soil infiltration rate - overland flow and erosion
soil permeability - drainage
water capacity of soil - water for transpiration
soil structure - root growth and aeration
cation capacity for retention - supplies for plants and buffer to acid rain
38
What binds cations in soil?
clay, needs H+ from carbonic acid from plant to release ions
39
NPP in different ecosystem
NPP higher in more productive ecosystems, so lower soil organic matter
40
Organic output is controlled by:
Temp and precip - higher = faster decomp
Type of plant tissue - rich in N and P decomp quickly
Soil properties - fertility, texture, fauna
41
Importance of organic matter in soils
improves structure and porosity
increases infiltration rate
increase available water capacity
supply nutrients to plants thru decomp
humus has high cation exchange capacity
42
What is ethnopedology?
Studying how different cultures around the world describe soils
43
What is the CSSC?
Canadian system of soil classification
- hierarchy from orders to families
44
What are the categorical levels in the CSSC? (5)
Order: properties that reflect environmental and soil forming processes
Great group: subdivision of order reflecting differences in dominant processes
Subgroup: differentiated by content and arrangement of horizons
Family: differences in texture, mineralogy, climate and chemistry
Series: detailed features of the pedon differentiate subdivisions of the family
45
What are soil horizons?
Layers named and standardized as diagnostic in classification process
- colour, texture
46
What are the types of horizons and how are the horizons include in them?
Mineral - A, B, C
Organic - O, L, F, H
47
What are the A horizons? (2)
A - mineral horizon near soil surface
Ah - accumulation of SOM
Ae - removal of clay, SOM, iron, or Al
48
Define B horizon and list all 8 suffixes.
B - accumulation of material from Ae horizon or by alteration of parent material
Bh - accumulation of SOM
Bf - accumulation of iron/Al
Bss - presence of slickensides (smooth clay coating caused by stress in clay soil)
Bv - vertic horizon caused by turbation (mixing) of material in high clay soils
Bt - accumulation of clay
Bn - strong soil structure and sodium accumulation
Bg - mattling and gleying due to water saturation
Bm - slight colour or structural changes from the parent material
49
Define C horizon and list all 5 suffixes.
C - horizon with little evidence of pedogenic activity
Cca - accumulation of Ca and Mg carbonates
Cs - accumulation of soluble salts
Ck - presence of original Ca and Mg carbonates
Css - presence of slickensides
Cg - mattling and gleying due to water saturation
50
Define R and W horizons.
R - consolidated bedrock
W - water layer
51
Define O horizon and list 3 types.
O - organic horizon developed mainly from bog or peat vegetation
Of - composed of fibrous materials of readily recognizable origin
Om - organic materials in an intermediate (or mesic) stage of decomp
Oh - organic material highly decomped (humic state)
52
Define L, F, and H horizon.
L - leaf litter
F - folic material (partially decomped leaf and twig)
H - humic material (decomposed organic with no original structures)
53
List 10 soils of CSSC.
Brunisolic
Cryosolic
Chernozemic
Gleysolic
Luvisolic
Organic
Podzolic
Regosolic
Solonetzic
Vertisol
54
Describe brunisols.
Under mixed forests
med fertility
slightly acidic
clay rich
brown, darker Ah, no Ae horizon
55
Describe podzolic soil.
Boreal forests
Acidic pH (due to vegetation litter)
Low to med fertility
Strongly leached
Distinct horizons with Fe, and organic matter transport
- Ah horizon, thin Ae
Bh, Bf, Bt
56
Describe luvisolic soil.
Under mixed forests
Usually middle step in soil succession
Rich in base cations
High fertility
pH more balanced
Ae, Bt horizons
57
Describe gleysolic soils.
In riparian landscapes
Shallow water table
Anoxic
Reduction of Fe3+ to Fe2+
58
Describe organic soils.
Waterlogged, anaerobic, cold
Not mineral soils
Formed by slow accumulation of org matter
Low fertility
Very acidic
59
Describe regosolic soils.
Soils beginning to develop
Form on young parent material
no B horizon
60
Describe vertisolic soils.
Cool subarid grasslands
High clay content
Little development of horizons
Shrinking and swelling with drying and moistening forms cracks
Quite fertile but difficult to farm
61
Describe chernozern soils.
Lots of soil organic carbon (dark)
Beneath prairies
Thick A horizon
Low leaching base cations
Neutral - alkaline pH
Fertile
Dissolved salts from top soil often precipirate in upper C horizon
62
Describe solonetzic soils
In prairies
Salt accumulation at surface in areas with high evapotranspiration
Upward movement of minerals
Alkaline
Variable fertility
63
Describe cryosolic soils.
Arctic landscapes
Shallow
Weak chemical development and horizon formation
Permafrost underneath
Cryoturbation mixes horizons
64
Describe how nutrients are added to soil (3), and which ones.
1. Weathering of minerals from rocks (rock derived - Ca, Mg, K, P)
2. death and decay of vegetation (litter, SOM - P, N)
3. Atmospheric deposition dry and wet (N, Ca, Mg, K)
65
Describe soil nutrient outputs. (4)
Plant uptake and harvest
Erosion
atmosphere (gaseous N)
Ground water table and streams (leaching and erosion)
66
What are nutrients?
Elements needed to maintain growth and metabolism
67
What nutrients do plants need?
C, H, O, N, P, K
68
What are micronutrients?
nutrients that are needed in very small concentrations
- Fe, Mn, Zn, Cu, B, Mo, Cl
69
Undisturbed and disturbed ecosystem nutrient cycling
Un - cycling is tight inputs = outputs
Disturbed - inputs and outputs are mismatched
70
Which nutrients are lost most easily?
N > K > Ca > P
71
How are nutrients retained?
Base cations (ca, Mg, K) on cation exchange complex (clay and SOM)
P on clay, Fe-Al oxides/hydroxides and sometimes Ca
N as NH4+ on clay but NO3- more mobile in soil
- ammonium can be in CEC
pH very important
72
Describe the nitrogen cycle.
Nitrogen fixation: incorp of N2 from atmosphere into soil system
Mineralization: decomp of organic matter to mineralize N as ammonium (NH4+)
Nitrification: conversion of NH4+ to nitrate (NO3-)
Denitrification: conversion of NO3- to N2 and nitrous oxide (N2O) by microbes (gases released to atmosphere)
Leaching: loss of soluble NH4+ and NO3- to surface and groundwater
Plants draw up nitrate
Some bacteria transform NO3- to NO2- also
73
Describe the phosphorous cycle.
Solubilization: dissolution of phosphorus from soil minerals
- can also be input by dust and decomp
- usually as PO4 3-
Sorption: chemical process by which P becomes attached to surfaces of soil particles (occlusion)
Mineralization: decomposition of organic matter (enzymatic (phosphotastes hydrolysis of organic P compounds) to release inorganic phosphate (PO4 3-) which is bioavailable
Immobilization: uptake of inorganic P by plants and microorganisms and subsequent transformation to soil organic P
Leaching: loss of soluble organic and inorganic P to surface- and ground-water.
74
Describe the relationship between P availability and pH.
Most available between 6-7 pH
Higher - fixation mostly as Ca phosphates
around 6 also reaction with silicates
lower pH more fixation by hydrous oxides of Fe, Mn, Al
Lower still and some chemical fixation by soluble Fe, Al, Mn
75
Describe the potassium cycle.
Solubilization: dissolution of potassium from soil minerals
Sorption: chemical process by which K+ becomes attached to surfaces of soil particles
Immobilization: uptake of K+ by plants and microorganisms
Leaching: loss of soluble K+ to surface- and ground-water
has no organic phase
76
What are deficiency symptoms of N, P, K?
N deficiency causes pale yellowish green corn plants with spindly stalks - middle
P deficiency visible on young corn plants
- Dark green with reddish purple leaf tips and margins
K deficiency first seen as yellowing and necrosis of corn leaf margins beginning on lower leaves - edges
77
What is eutrophication?
Excessive algae growth caused by added nutrients leached from fertilizer etc
Leads to degradation of ecosystem, fish kills, and contamination of water supply
Fish calls caused by oxygen deprivation
78
What are some solutions to dead zones?
Reduced fertilizer application rates and increase efficiency in application
Point source pollution from improved wastewaters treatment and bans of phosphate in detergents
Nature based solutions (ex. Riparian buffer strips and wetland restoration)
- riparian buffers intercept nutrients before streams
79
Explain proximate vs ultimate limitation.
While N contamination has been substantially reduced, P concentrations in waters remain too high (P lasts in long time - is ultimate limiting)
Distinction between proximate and ultimate limiting nutrient
Addition of proximate limiting nutrient stimulate biological processes and growth
Addition of ultimate limiting nutrients leads to a transformation of whole ecosystems/species composition .
80
What is soil erosion?
Wearing away of topsoil by natural physical forces of water and wind or through human activities
Topsoil (high in SOM, fert, and life) is detached, moved, and deposited elsewhere
Reduces productivity and contributes to pollution of water
81
What are the 5 types of erosion?
Soil creep: slow downslope movement of soil particles in response to disturbances - expansion/contraction with wetting/drying, soil faunal activity, etc
- Increases with slope angle
Landslides and earthflows: rapid mass movements when soil strength exceeded by gravity, usually follows heavy rainfall
Fluvial: by running water (most important type!!)
Aeolian: wind removal of surface layer; requires absence of protective vegetation cover, dry soils, and strong winds
Wind erosion caused by lack of vegetation, dry soil, and strong winds
82
Describe the fluvial erosion process.
Raindrop impact and splash (displacement and loosening)
Creation of overland flow (transport)
Deposition (on slope or at bottom)
- can suffocate seedlings, has no structure, can reduce # redox reactions
83
Describe the 3 types of water erosion.
Sheet - erosion of whole area (most severe)
Rill - small channels eroded
Gully - larger deeper channels
84
How can we measure soil erosion rates and what are the problems?
Collect soil downslope in troughs or measure loss of soil against stable surface
problems
- Large temporal and spatial variability
- Labour intensive
- Difficult to scale up from small plots to drainage basins and landscapes
- Of little predictive value
85
What is the universal soil loss equation?
A = R*K*LS*C*P
A = erosion rate (tons/ha/yr)
R = rainfall erosivity
K = soil erodibility
LS = combination of length and slope of field
C = crop type
P = conservation measures applied
86
Describe rainfall erosivity (R).
Potential of rain to erode soil
Combination of rainfall intensity (affects overland flow creation more in tropics) and rainfall energy (ability to splash soil particles downslope and destroy soil aggregates)
87
Describe soil erodibility (K)
Potential of soil to become eroded.
Combination of
1. Soil infiltration rate (sand > loam > clay)
2. Ease of detachment of soil particles (silt > clay > sand)
3. Ease of transport of soil particles (clay > silt > sand > gravel)
88
Describe soil length factor (LS)
Combination of
1. Longer slopes mean greater cumulative overland flow from upslope, leading to faster movement, thicker layer and greater capacity to erode and carry soil
2. Steeper slopes mean faster overland flow and greater capacity to erode and carry soil
89
Describe crop (C) and conservation (P) values.
Crop - forest 0.0001, grass 0.01-0.02, corn 0.2-0.5, cotton 0.4-0.7, bare soil 1
Conservation - contour ploughing 0.6-0.9, terracing 0.1-0.3, none 1
90
What conservation measures can we implement to lower erosion rate?
Can change slope angle - terraces
Change slope length by dividing with trees or hedges
Mix up crops and get lower C value (cover crops)
91
Environmental effects of accelerated rates of soil erosion on site
Reduced water availability from soil
- Increases surface runoff
- Removes fine particles leaving sand and gravel particles which have lower available water capacity, and thus ability to store water and supply crops
Reduced soil fertility
- Loss of fertilizers
- Removes smallest particles which have highest available nutrient content and cation exchange capacity
Reduced rooting depth (shallower soils)
Gully creation loses agricultural land and increases accessibility costs of farming
Greater energy costs for agricultural needs
Positive feed-back
92
Reducing soil erosion in agricultural systems
Change crop type or planting/harvesting schedules (C)
Protect soil surface and increase infiltration rate - add organic matter or change tillage practices (K)
Change length and angle of field by creating terraces or ploughing parallel to slope (LS)
Reduce grazing densities to allow grass cover: >25% grass cover is critical in reducing erosion (C)
93
Reducing soil erosion in forest sites
Reduction of timber harvest (clearcutting only on gentle slopes)
Suitable methods of tree removal (using horses instead machinery)
Scheduling of harvest during dry season or when ground is frozen
Design and management of roads and skidding trails
Buffer strips along stream channels - makes sure things do not get into streams
94
Off site effects of accelerated soil erosion
Sedimentation of eroded soil in water (880 millions tons/year in US)
Eutrophication of water bodies
- N and P transported adsorped to eroded soils
- Also pesticide transport
Deterioration of water quality and higher water treatment costs
Increased frequency of flooding - greater surface runoff and channel volume reduced by sediments
95
Describe 3 types of wind erosion and how to prevent wind erosion
Creeping - larger particles creeping on surface
Saltation - particles being lifted and moved in same general area
Suspension - particles picked up and taken away
How to prevent
Soil moisture
Soil cover
Tillage
Barriers
96
What types of organisms can be found in soil?
Macrofauna - mammals, reptiles, insects, earthworms
Microfauna - nematodes, protozoa, rotifers
Flora - plant roots, algae, fungi, actinomycetes (filamentous bacteria), bacteria
97
Describe biomass of organisms in different regions?
Warmer - more macro, cooler - more micro
98
Describe the 4 major groups of microorganisms.
Bacteria:
10^6 to 10^9 per gram of soil
Great variety and metabolic pathways, important in chemical decomp of organic matter and chemical transformations
Algae:
Both terrestrial and aquatic forms
Important because of ability to fix atmospheric N2 into organic and inorganic forms
10^5 per gram of soil, mainly close to surface (dependent on photosynthesis)
Usually colonize surface of cooled lava flow (important in succession)
Protozoa:
Parasites and predators, regulating microbial communities
10^4 per gram soil
Fungi:
Comprising filaments up to 20 micrometers in diameter branching through soil
10^6 to 10^9 per gram soil
Displace bacteria in acidic nutrient poor soil, in decomposing recalcitrant tissues, such as wood
99
What is the rhizosphere? What is mycorrhizae?
Rhizosphere: where plant roots meet soil
Mycorrhizae: fungal connections with plant roots that draw P and other nutrients up and provide to plants to get glucose
100
What direct and indirect and positive and negative effects do root exudates have in rhizosphere?
Direct + (overall positive)
- induces nodule formation, stimulates mycorrhizal infection, increase nutrient availability, improves soil water holding capacity
Indirect +
- supports associative N2 fixation and transfer of N to plant, induces plant hormone production
Direct -
- induces fungal pathogen growth, attracting nematodes
Indirect -
- immobilization of nutrients
101
What are positive effects of mycorrhiza in agriculture and how can this be promoted?
+ effects
Enhanced nutrient uptake (particularly P)
Water supply
Pest control (ex. nematodes)
Soil stabilization - acid and protein rich gel helps root growth
Promotion through
Organic farming
Cultivation of crops that develop this (legumes, corn, potato, sunflowers)
Continuous soil cover
Mild soil tillage practice
102
Give some examples of ecosystem engineers
Earthworms, termites, prairie dogs
103
How do earthworms effect soil properties?
ingest and excrete topsoil
Affect soil structure and soil nutrient availability by mixing of organic and mineral fractions and stimulating decomposition of organic
increases nutrient availability
104
Describe patterns of earthworm biomass distribution.
Most in temperate pastures, then other forests and prairies, then taiga
Less landuse = more worms and more soil consumption
Earthworms correlate with glaciation location
105
How do termites and mounds modify soil?
Sandy, stuck together by mucus that termites produce
Water availability higher because mucus (helps with water and organic matter retention)
Termites bring plants and litter through channels, digested, and N and P enriched in area
Abandoned termite mounds can become islands of high soil fertility
Greater availability of P, K, Ca, and H2O retention capacity
Once abandoned islands begin growing trees and vegetation lasts longer
106
How do prairie dogs impact soil?
Tunnel system and mounds
pH higher closer to entrance
