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ENST200 > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

Soil pH impact on growth and functioning of soil organisms

A

-greatly influences root uptake availability of nutrients
-influences activity of microorganisms and type of vegetation
-affects mobility of pollutants in soil
-controls chemistry of soils and waters

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2
Q

Hydrogen ions

A

cause acidity

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3
Q

combination pH electrode

A

measuring soil pH with H+ selective glass electrode

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4
Q

how do soils become acid

A

addition of H+ ions from acid-forming processes
exchange of 2 H+ ions for a Ca2+ ion
Anions of acids –> leaching loss of Ca, Mg, K, and Na

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5
Q

Production of H+

A

carbonic acid from CO2
organic acid dissociation
oxidation of N and S
cation uptake
cation ppt

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6
Q

consumption of H+

A

carbonate input
organic anion protonation
reduction of N, S, Fe
anion uptake
cation weathering

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7
Q

role of Al in soil acidity

A

Al3+ ions have a tendency to hydrolyze
Al3+ combines with OH- leaving the H+ to lower the pH of the soil solution

a single Al3+ ion can release up to 3 H+ ions

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8
Q

bufferring capacity

A

ability of the soil to resist change in pH as a result of reserve and exchangeable activity

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9
Q

factors to consider when using lime

A

-plant’s soil pH preference
-soil properties
-initial pH
-soil buffering capacity
-amount of soil to be treated
-nature of liming material

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10
Q

human influenced soil acidification

A

-natural processes of acidification accelerated
-nitrogen amendments
-acid precipitation
-exposure of potential acid sulfate soils

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11
Q

acid rain

A

gaseous and particulate pollutants in atmosphere –> cloud water –> rain

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12
Q

effects of acid rain

A

weathers marble and structures
vegetation damaged from the top down

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13
Q

acid mine drainage

A

exposed pyrite reacts with water and oxygen to form sulfuric acid

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14
Q

acid soils are prominent in

A

humid climates with intense weathering and leaching

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15
Q

basic soils are prominent in:

A

arid climates with a lack of weathering or leaching

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16
Q

alkalinizing processes that consume H+ or produce OH-

A

-weathering of nonacid cations from minerals
-accumulation of nonacid cations
-production of base-producing anions
-excess anion uptake by roots

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17
Q

causes of soil salinity

A

-rainfall
-irrigation with poor drainage
-capillary rise followed by evaporation
-landforms
-de-icing salt
-salt water intrusion

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18
Q

major salts in soil salinity

A

cations
-sodium
-calcium
-magnesium

anions
-chloride
-sulfate
-bicarbonate
-carbonate
-nitrate

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19
Q

salt-affected soil impacts on plants

A

-toxicity of: sodium, boron, chloride, bicarbonate
-cation imbalance
-soil dispersion by sodium
-water stress

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20
Q

salinity

A

high total dissolved salts

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21
Q

sodicity

A

high exchangeable sodium

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22
Q

what makes (saline) sodic soil alkaline

A

-salts split water molecules into H+ or OH-
-carbonates
-bicarbonates
-carbonate and bicarbonate react with water to release hydroxyls
-solubility at high pH

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23
Q

soil organisms major flows

A

energy, mineral nutrients, carbon

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24
Q

macrofauna

A

> 2 mm
earthworms, gophers, cicadas, ants

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25
mesofauna
0.2 mm - 2 mm mites, deer ticks, tardigrade
26
microfauna
< 0.2 mm nematodes, springtails, protozoa
27
soil flora
plants, plant roots, fine feeder roots and root hairs
28
lichens
some make nitrogen in the air usable to plants homes for spiders, mites, lice, other insects
29
cryptobiotic crust
dominated by cyanobacteria if crust is busted, soil will erode away
30
cryptobiosis
hidden life
31
microorganism ecosystem services
-capture N from air and convert to plant available form (nitrogen fixation) -decompose organic debris -produce growth-promoting and growth-inhibiting compounds -stabilize and mobilize metallic ions and colloids -serve as foundation of food chain
32
Chemoheterotrophs
biochemical oxidation and organic carbon
33
photoheterotrophs
solar radiation and organic carbon
34
chemoautotrophs
biochemical oxidation and carbon dioxide
35
photoautotrophs
solar radiation and carbon dioxide
36
ecological engineers
organisms that make major alterations to their physical environment and influence the habitats of many other oragnisms
37
abundance, biomass, and metabolic activity numbers influenced by:
-amount and quality of food available -physical factors -biotic factors -chemical factors
38
earthworms like
well drained soils lots of high N OM lots of Ca mulched soils
39
earthworms dislikes
sharp sandy soils very acid soils very wet or very dry soils shallow soils bare soils tillage
40
earthworms impacts
-incorporate OM -make burrows, channels -improve aggregation -excrete worm casts in or on soil -improve drainage, aeration, infiltration -enhance nutrient availability and cycling
41
epigeic earthworms
live close to surface and feed on plant litter
42
aneic earthworms
feed on plant litter and soil adn form early vertical burrows
43
endogeic earthworms
live at various depths in mineral soil horizons and feed on soil
44
termites
transport soil from depth to the surface, mixing and incorporating plant residues
45
nematodes
-when soil becomes too dry, they survive by coiling into cryptobiotic resting state -feed on fungi, bacteria, algae, or nematodes, protozoa, and insect larvae -stimulate cycling and release of plant available nitrogen
46
nematode control
-long rotations with non-host crops -use of genetically resistant crop varieties -soil fumigation with highly toxic nematocides -use of hardwood bark in container plantings -interplanting or rotating susceptible crops with plants like marigolds that produce root exudates with nematocidal properties
47
protozoa
mobile, single-celled creatures that capture and engulf their food thrive best in well drained soils and are must abundant in surface horizons most prey on bacteria
48
3 pools of acidity
active acidity salt-replaceable acidity residual acidity
49
active acidity
quantity of hydrogen ions that are present in the soil solution
50
salt-replaceable acidity
involving the aluminum and hydrogen that are easily exchangeable by other cations in simple unbuffered salt solution
51
residual acidity
can be neutralized by limestone or other alkaline materials but cannot be detected by the salt replacement
52
types of salt affected soils
saline saline sodic sodic
53
fungi dominate
acidic soils sandy soils fresh organic residue
54
soil fungi activities
-decomposers of organic materials -participate in nutrient cycling -hyphae stabilize the soil structure -some species compete by generating substances toxic to other fungi and bacteria -some species trap nematodes
55
mycorrhizal fungi benefits to plant
-enhanced nutrient uptake -generally all types can transport N and P -formation of soil macroaggregates -defense of plants
56
Eukaryotes
animal, plant, fungi, protists
57
prokaryotes
no nucleus surrounded by a membrane archaea and bacteria
58
coccus
round
59
bacillus
rodlike
60
spirillum
spiral
61
soil prokaryote metabolism
Aerobic, Facultative, or Anaerobic prefer pH 7-8 live almost anywhere some can fix nitrogen from air
62
symbiosis mutualism example of soil prokaryotes
rhizobia bacteria fix nitrogen in root nodules on legume plants
63
cyanobacteria
can photosynthesize fix atmospheric nitrogen into plant available tolerance to saline environment...form cryptobiotic crusts on desert soils
64
actinomycetes
-filamentous, branched bacteria -breakdown resistant compounds (cellulose, chitin, phospholipids) -important in composting -petrichor :)
65
conditions affecting growth of soil microorganisms
-organic matter requirements (competition) -oxygen, moisture, and temperature -exchangeable cations and pH
66
beneficial effects of soil organisms on plant communities
-organic matter decomposition -breakdown of toxic compounds in soil -inorganic transformation keeps levels of available Fe and Al in check (oxidation) -nitrogen fixation
67
beneficial effects of soil microorganisms
-decomposition or organic matter -inorganic mineral transformation -plant-microbe mutualism
68
harmful effects of soil microorganisms
-pathogenic activity -competition for nutrients -some mineral transformation -production fo toxins -competition for oxygen
69
practices that decrease diversity adn abundance of soil organisms
fumigants, nematicides, some insecticides, compaction, soil erosion, industrial wastes, heavy metals, plowing and tillage, monocropping, row crops, bare fallow periods, residue burning or removal, plastic mulches
70
practices that enhance diversity and abundance of soil organisms
balanced fertilization, lime on acid soils, proper irrigation, improved drainage/aeration, animal manures and composts, clean sewage sludge, reduced or zero tillage, crop rotations, grass-legume pastures, cover crops, mulch fallows, residue return to soil surface, organic mulches
71
ash
anything thats not oxygen and carbon that makes up plants
72
decomposition of organic compounds
fast to slow: -sugars, starches, and simple proteins -crude proteins -hemicellulose -cellulose -fats and waxes -lignin and phenolic compounds
73
R-strategists
opportunist organisms respond to food source when fresh residues are added once food source is eaten, their population declines
74
K-strategists
only slow growing steady populations remain when residues well stabilized
75
factors controlling rate of decomposition
-environmental conditions (sufficient soil moisture, adequate aeration, soil temperature, soil structure) -quality of the added residues as a food source
76
carbon nitrogen ratio of residue
if ratio exceeds 25:1, the microbes will have to scavenge to obtain enough N, depleting soils supply to soluble N, leading to N deficiency in plants C:N>30 --> likely to tie up N C:N<20 --> likely to release N
77
soil organic matter
-sequesters global C -fuels the soil food web -enhances soil physical properties -controls the cycling of most nutrients -a storehouse for sulfur, phosphorus, nitrogen
78
carbon in
-plant litter -animal wastes -imported bio-products -rhizodeposition -root residues
79
carbon out
-oxidation -removal C -erosion -organic C leaching out
80
increase SOM levels by
-soil conservation -green manures/cover crops -return/mulch of plant residues -controlled grazing -composts and manure -appropriate nitrogen levels -high plant productivity -year round and perennial vegetation
81
decrease SOM levels by
-erosion -intensive tillage -whole plant removal -high temperatures -overgrazing -dry soil conditions -high temperature/direct sun -fire -excessove mineral nitrogen -low plant productivity, especially roots
82
influence of OM on physical soil properties
-surface horizons dark brown or black colors -aggregation of soil -humus helps reduce cohesion and stickiness of clay -increases soil water retention
83
influence fo OM on chemical soil properties
-humus generally accounts for 50-90% of the CEC -humus colloids hold nutrient cations in easily exchangeable forms -functional groups produce pH buffering capacity -humic acids attack soil minerals and accelerate decomposition --> release nutrients -SOM can alleviate Al toxicity
84
Influence of OM on biological soil properties
-provides most of the food for the heterotrophic organisms

ENST200 (5 decks)

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