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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
Q

mesofauna

A

0.2 mm - 2 mm
mites, deer ticks, tardigrade

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26
Q

microfauna

A

< 0.2 mm
nematodes, springtails, protozoa

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27
Q

soil flora

A

plants, plant roots, fine feeder roots and root hairs

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28
Q

lichens

A

some make nitrogen in the air usable to plants
homes for spiders, mites, lice, other insects

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29
Q

cryptobiotic crust

A

dominated by cyanobacteria
if crust is busted, soil will erode away

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30
Q

cryptobiosis

A

hidden life

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31
Q

microorganism ecosystem services

A

-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

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32
Q

Chemoheterotrophs

A

biochemical oxidation and organic carbon

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33
Q

photoheterotrophs

A

solar radiation and organic carbon

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34
Q

chemoautotrophs

A

biochemical oxidation and carbon dioxide

35
Q

photoautotrophs

A

solar radiation and carbon dioxide

36
Q

ecological engineers

A

organisms that make major alterations to their physical environment and influence the habitats of many other oragnisms

37
Q

abundance, biomass, and metabolic activity numbers influenced by:

A

-amount and quality of food available
-physical factors
-biotic factors
-chemical factors

38
Q

earthworms like

A

well drained soils
lots of high N OM
lots of Ca
mulched soils

39
Q

earthworms dislikes

A

sharp sandy soils
very acid soils
very wet or very dry soils
shallow soils
bare soils
tillage

40
Q

earthworms impacts

A

-incorporate OM
-make burrows, channels
-improve aggregation
-excrete worm casts in or on soil
-improve drainage, aeration, infiltration
-enhance nutrient availability and cycling

41
Q

epigeic earthworms

A

live close to surface and feed on plant litter

42
Q

aneic earthworms

A

feed on plant litter and soil adn form early vertical burrows

43
Q

endogeic earthworms

A

live at various depths in mineral soil horizons and feed on soil

44
Q

termites

A

transport soil from depth to the surface, mixing and incorporating plant residues

45
Q

nematodes

A

-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
Q

nematode control

A

-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
Q

protozoa

A

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
Q

3 pools of acidity

A

active acidity
salt-replaceable acidity
residual acidity

49
Q

active acidity

A

quantity of hydrogen ions that are present in the soil solution

50
Q

salt-replaceable acidity

A

involving the aluminum and hydrogen that are easily exchangeable by other cations in simple unbuffered salt solution

51
Q

residual acidity

A

can be neutralized by limestone or other alkaline materials but cannot be detected by the salt replacement

52
Q

types of salt affected soils

A

saline
saline sodic
sodic

53
Q

fungi dominate

A

acidic soils
sandy soils
fresh organic residue

54
Q

soil fungi activities

A

-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
Q

mycorrhizal fungi benefits to plant

A

-enhanced nutrient uptake
-generally all types can transport N and P
-formation of soil macroaggregates
-defense of plants

56
Q

Eukaryotes

A

animal, plant, fungi, protists

57
Q

prokaryotes

A

no nucleus surrounded by a membrane
archaea and bacteria

58
Q

coccus

A

round

59
Q

bacillus

A

rodlike

60
Q

spirillum

A

spiral

61
Q

soil prokaryote metabolism

A

Aerobic, Facultative, or Anaerobic
prefer pH 7-8
live almost anywhere
some can fix nitrogen from air

62
Q

symbiosis mutualism example of soil prokaryotes

A

rhizobia bacteria fix nitrogen in root nodules on legume plants

63
Q

cyanobacteria

A

can photosynthesize
fix atmospheric nitrogen into plant available
tolerance to saline environment…form cryptobiotic crusts on desert soils

64
Q

actinomycetes

A

-filamentous, branched bacteria
-breakdown resistant compounds (cellulose, chitin, phospholipids)
-important in composting
-petrichor :)

65
Q

conditions affecting growth of soil microorganisms

A

-organic matter requirements (competition)
-oxygen, moisture, and temperature
-exchangeable cations and pH

66
Q

beneficial effects of soil organisms on plant communities

A

-organic matter decomposition
-breakdown of toxic compounds in soil
-inorganic transformation keeps levels of available Fe and Al in check (oxidation)
-nitrogen fixation

67
Q

beneficial effects of soil microorganisms

A

-decomposition or organic matter
-inorganic mineral transformation
-plant-microbe mutualism

68
Q

harmful effects of soil microorganisms

A

-pathogenic activity
-competition for nutrients
-some mineral transformation
-production fo toxins
-competition for oxygen

69
Q

practices that decrease diversity adn abundance of soil organisms

A

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
Q

practices that enhance diversity and abundance of soil organisms

A

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
Q

ash

A

anything thats not oxygen and carbon that makes up plants

72
Q

decomposition of organic compounds

A

fast to slow:
-sugars, starches, and simple proteins
-crude proteins
-hemicellulose
-cellulose
-fats and waxes
-lignin and phenolic compounds

73
Q

R-strategists

A

opportunist organisms respond to food source when fresh residues are added
once food source is eaten, their population declines

74
Q

K-strategists

A

only slow growing steady populations remain when residues well stabilized

75
Q

factors controlling rate of decomposition

A

-environmental conditions (sufficient soil moisture, adequate aeration, soil temperature, soil structure)
-quality of the added residues as a food source

76
Q

carbon nitrogen ratio of residue

A

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
Q

soil organic matter

A

-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
Q

carbon in

A

-plant litter
-animal wastes
-imported bio-products
-rhizodeposition
-root residues

79
Q

carbon out

A

-oxidation
-removal C
-erosion
-organic C leaching out

80
Q

increase SOM levels by

A

-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
Q

decrease SOM levels by

A

-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
Q

influence of OM on physical soil properties

A

-surface horizons dark brown or black colors
-aggregation of soil
-humus helps reduce cohesion and stickiness of clay
-increases soil water retention

83
Q

influence fo OM on chemical soil properties

A

-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
Q

Influence of OM on biological soil properties

A

-provides most of the food for the heterotrophic organisms

ENST200 (5 decks)

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