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General Ecology > Nutrient Cycling > Flashcards

Nutrient Cycling Flashcards

1
Q

What are dead zones like for most aquatic life?

A

hypoxic

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2
Q

How have dead zones changed in recent years?

A

nearly doubled in size

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3
Q

How are dead zones in terms of nutrients?

A

eutrophic due to excess N and P input from agriculture, livestock, suburban lawns, and sewage

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4
Q

What happens with algae in terms of dead zones?

A

algae growing in upper level diem sink to lower depths, and detrivores use up O2 as they decompose the dead cells

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5
Q

What ranges are there for dead zones?

A

40 km^2 to 22,000 km^2,

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6
Q

Where are dead zones in rivers

A

freshwater from river layers on top of salt water

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7
Q

Why do dead zones have vast ranges?

A

some effect of variation in water layer, but strong effect of nutrient input

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8
Q

What is the only long term solution for dead zones?

A

reducing nutrient inputs permanently

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9
Q

What are macronutrients?

A

most important to building biological molecules, present in high amounts

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10
Q

What are the macronutrients?

A

C, H, O, N, P, S

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11
Q

What form of macronutrients is used by primary producers?

A

inorganic (ex CO2)

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12
Q

What form of macronutrients is used by consumers?

A

organic (ex C, H, O, N, and S in proteins)

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13
Q

Where is N and S found?

A

in protein and nucleic acids

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14
Q

Where is P found?

A

in nucleic acids and lipids

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15
Q

What macronutrients do carbohydates have?

A

C, H, and O

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16
Q

What does decomposition (mineralization) release?

A

inorganic forms of nutrients from organic forms

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17
Q

What do nutrients cycle between?

A

organic and inorganic pools (internal flux)

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18
Q

What is external flux?

A

inputs from outside and exports to outside

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19
Q

What is the law of conservation of mass?

A

matter is neither created nor destroyed, all it does it cycle in and out of different forms (transformation)

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20
Q

What are the main pools in the forest carbon cycle?

A
  • atmospheric CO2
  • plant carbon
  • soil carbon
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21
Q

What are the main fluxes in forest carbon cycle?

A
  • photosynthesis (carbon fixation)
  • plant respiration
  • soil respiration
  • litter fall
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22
Q

What are micronutrients?

A

present in small amounts, essential to most life forms

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23
Q

What is Leibig’s Law of the Minimum?

A
  • the nutrient that is in lowest supply relative to its demand by an organism is its limiting nutrient
  • if nutrient is supplied in sufficient amounts, another nutrient will become limiting
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24
Q

How can limiting nutrient be identified?

A

experimentally via nutrient addition bioassays that add nutrients individually

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25
Q

What are the most often limiting nutrients?

A

N and P, often co-liminiting

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26
Q

What is a co-limiting nurtrient?

A

needed together with another nutrient to stimulate growth

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27
Q

Where is emphasis being placed on in terms of controlling lake eutrophication?

A

controlling non-point sources

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28
Q

What are the pools for forest phosphorous cycle?

A
  • soil inorganic P
  • soil organic P
  • plant P
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29
Q

What are the fluxes for forest phosphorous cycle?

A
  • plant uptake
  • soil organism immobilization
  • soil organism mineralization
  • litter fall
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30
Q

What does the size of each nutrient pool depend upon?

A

the fluxes among pools

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31
Q

What are pools like in mature forests?

A

generally have staple nutrient pools (in equilibtium)

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32
Q

What do sources do?

A

add nutrients to an ecosystem

33
Q

What are sinks?

A

locations where nutrients go when leaving an ecosystem

34
Q

What do anabolic reactions do?

A

building of complex biological (organic) molecules

35
Q

What do catabolic reactions do?

A

break down of complex molecules to simpler molecules

36
Q

How are anabolic and catabolic reactions linked?

A

via stoichiometry related to the ratios of atoms in molecules

37
Q

Why do nutrients cycle?

A

due to the Law of Conservation of Mass

38
Q

Why does energy flow>

A

due to first and second law of thermodynamics

39
Q

What are many fluxes in forest nitrogen cycle mediated by?

A

soil microbes (bacteria and fungi)

40
Q

What do microbes do when “feeding” on low quality (high C:N ratio) organic matter?

A

immobilize for NH4+ and NO3-

41
Q

What does impervious substrate mean?

A

inputs from atmospheric sources and weathering of soil inorganic materials could be balanced with outputs in stream water

42
Q

What did the Hubbard Brook watershed experiment study?

A

the effect of deforestation on the N cycle by comparing 2 watersheds

43
Q

What did deforestation do in Hubbard brook experiment?

A

reduced plant uptake, increased microbial mineralization and nitrification, and much NO3- was leached from the soil

44
Q

What losses were high as a result of deforestation in Hubbard Brook experiment?

A

aluminum and calcium

45
Q

What happened to stream pH in hubbard brook experiment?

A

pH dropped years following deforestation

46
Q

What is acid rain produced by?

A
  • NOx produced by soil bacteria and burning of fossil fuels
  • SOx emissions
47
Q

What pH does acid rain have?

A

around 4

48
Q

What happens in acid rains in terms of ions?

A

H+ ions from acid raid displace positively charged ions causing leaching from the soil

49
Q

What does caustic acid rain do?

A

“burns” foliage and causes direct harm to plants and mobilizes toxic Al, thus poisoning plants

50
Q

What is main plant uptake in aquatic ecosystems done by?

A

algae and rooted macrophages

51
Q

What happens to N in aquatic ecosystems?

A

organic and inorganic N is moved downstream in streams and tends to sink in lakes and oceans

52
Q

Where does N cycle occur in thermally stratified bodies of water?

A

may occur primarily in upper layer (epilimnion) unless thermal mixing with the lower layer (hypolimnion) occurs

53
Q

What does mixing do?

A

bring nutrients back up to surface

54
Q

Where are most accurate assessments of nutrient budgets made?

A

in defined watersheds with impervious substrates (bedrock)

55
Q

What can be used to calculate retention and storage rates when assuming other losses are minimal?

A

inputs via atmosphere and outputs via streamflow

56
Q

What does nutrient budget ignore?

A

internal cycling

57
Q

What can mitigation of nutrient retention problems in urban environments be mitigated by?

A

animal waste control, street sweeping, fertilizer reduction, retention ponds

58
Q

What can retention ponds reduce?

A

direct run off, allowing time for processes such as denitrification and leaching to groundwater to reduce inputs to streams

59
Q

Can modified nutrient budgets accurately calculate storage rate?

A

no

60
Q

How can modified nutrient budgets be calculated?

A

using only focal inputs and stream outputs (ignoring natural inputs)

61
Q

What kind of loop are global biogeochemcial cycles?

A

closed loops

62
Q

What do pre-historic global phosphorous cycle shows?

A

balance among atmospheric, oceanic, terrestrial, and geologic components before humans altered it by making phosphorous fertilizers

63
Q

What exchange dominates in ocean carbon cycle?

A

atmospheric exchange vs surface and deepwater exchange

64
Q

What is the largest carbon pool?

A

oceanic reserve

65
Q

What exchange is in terrestrial carbon cycle?

A

photosynthesis inputs vs plant and soil respiration and fire outputs

66
Q

How does litterfall influence exchange?

A

between aboveground and soil carbon pools

67
Q

What has burning of fossil fuels increased?

A

atmospheric carbon (CO2)

68
Q

What does the International Panel on Climate Change examine?

A

several future scenarios
- increasing affluence, regionality, green growth

69
Q

In IPCC scenarios, when are carbon emissions highest and lowest?

A

highest with Regionality and lowest with Green Growth

70
Q

Where does most excess carbon end up?

A

atmospheric pool

71
Q

Since elevated CO2 is associated with higher greenhouse effect, what is expected to happen in all scenarios of IPCC?

A

global temp rise

72
Q

What are negative feedback cycle and example

A
  • dampen initial change
  • effect of elevated CO2 plant growth
73
Q

What is prositive feedback cycle and example?

A
  • amplify initial change
  • effect of elevated CO2 on decomposition rates or fire frequency/intensity
74
Q

What is the largest N pool?

A

atmosphere

75
Q

What has Haber-Bosch process allowed for?

A

production of NH3-based fertilizers from atmospheric N2

76
Q

What has also increased bioavailability of N in terrestrial and atmospheric systems?

A

crop N-fixation and increased burning

77
Q

How is acid rain resulting from SOx partly solved?

A

by cap and trade of SOx emission from major fossil fuel burners, particularly coal-fired electrial generating plants

78
Q

What may mitigation of excess nutrients involve?

A

modeling scenarios whereby various costs and benefits can be estimated

General Ecology (24 decks)

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