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BIOL 208 > Nutrient Cycling > Flashcards

Nutrient Cycling Flashcards

1
Q

What is the Redfield Ratio?

A

106C:16N:1P
Elemental composition of our planet’s biomass

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2
Q

What do all nutrient cycles have in common?

A

Common elements have cycles that include biotic and abiotic pools
Elements that are required for the development, maintenance, and reproduction of organisms are called nutrients

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3
Q

Where is phosphorus limiting?

A

In aquatic ecosystems

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4
Q

What is phosphorus essential to?

A

Energetics, genetics, structure of living organisms
Is not abundant in the biosphere

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5
Q

What is the ultimate reservoir of phosphorus?

A

Rock

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6
Q

What does the phosphorus cycle look like?

A

Marine sediments -> sedimentary rocks -> incorporation into soils, via weathering -> available for active cycling

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7
Q

Where is nitrogen limiting?

A

In marine and terrestrial ecosystems

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8
Q

What is nitrogen essential in?

A

Key biomolecules including amino acids, nucleic acid, chlorophyll, and hemoglobin

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9
Q

What is the ultimate reservoir of nitrogen?

A

In the atmosphere in the form of N2 gas

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10
Q

How does nitrogen fixation occur?

A

Via specialized organisms, lightning, and industrial production of fertilizer is the primary avenue by which nitrogen can enter ecosystems

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11
Q

What is nitrogen fixation?

A

Energetically costly
Specialized bacteria enable N input into ecosystems

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12
Q

What is ammonification?

A

Release of nitrogen as ammonium (NH4+) following decomposition by bacteria and fungi
Excretion of ammonium by all organisms

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13
Q

What can ammonium be taken up by?

A

Bacteria and primary producers

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14
Q

What is nitrification?

A

Conversion of ammonium to nitrite and then quickly nitrate

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15
Q

What can directly take up nitrite/nitrate?

A

Bacteria and primary producers

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16
Q

What is denitrification?

A

Conversion of nitrate to nitrous oxide, then dinitrogen gas
This change in redox state allows bacteria to use this conversion, instead of oxygen, to break down organic matter
No uptake occurs during this process
Denitrification is the primary mechanism through which nitrogen is lost from ecosystems

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17
Q

Why is carbon important?

A

It is the backbone of all organic molecules

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18
Q

What do carbon gasses play a role in?

A

A critical role in controlling climate change

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19
Q

How is carbon removed from the atmosphere?

A

By photosynthesis

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20
Q

How is carbon returned to the atmosphere?

A

By respiration

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21
Q

What is decomposition?

A

The process by which organic matter is decomposed to CO2 by microbes and nutrients are release for uptake by primary producers

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22
Q

What is the production of organic material at the base of food webs tied to?

A

Nutrients via nutrient limitation

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23
Q

What controls the availability of nutrients?

A

The rate of nutrient regeneration by decomposition

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24
Q

What is the speed of decomposition controlled by?

A

Moisture, temperature, organic matter composition

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25
Q

How does moisture affect decomposition?

A

More moisture results in faster decomposition

26
Q

What does decomposition increase with?

A

Increasing evapotranspiration

27
Q

What is evapotranspiration?

A

A measure of the total amount of water that evaporates and transpires off of a landscape
Increases with increasing temperature and increasing precipitation

28
Q

How does organic matter composition affect decomposition?

A

Increases in nutrient concentrations are high relative to carbon in the organic matter being decomposed
Decreases when organic matter is tough or contains a lot of structural tissue

29
Q

What is nutrient cycling like in aquatic ecosystems?

A

Autotrophs tend to be short lived
Autotroph biomass removed by zooplankton at a higher rate than terrestrial autotroph biomass is being consumed by terrestrial herbivores
Greater proportion of autotrophs consumed by herbivores than by detritivores compared to terrestrial system

30
Q

What do boxes depict in the carbon cycle diagram?

A

Boxes depict pools of immobilized carbon
The larger the box, the more C is immobilized

31
Q

What are the C pools like in aquatic systems as compared to terrestrial systems?

A

C pools of autotrophs are smaller in aquatic systems, given higher relative consumption rate by herbivores

32
Q

Is carbon flow from autotrophs to herbivores larger in aquatic or terrestrial systems?

A

Slightly larger in aquatic systems

33
Q

What is the implication of a lower rate of consumption in terrestrial ecosystems for carbon?

A

There is relatively more carbon immobilized as detritus and detritivores

34
Q

How quick is the cycling of nutrients in aquatic ecosystems?

A

Higher herbivory rates leads to less autotroph biomass which leads to less detritus which leads to less detritivore biomass
Overall quicker cycling of nutrients

35
Q

How quick is the cycling of nutrients in terrestrial ecosystems?

A

Lower herbivory rates leads to more autotroph biomass which leads to more detritus which leads to more detritivore biomass
Overall slower cycling of nutrients

36
Q

What about nutrient cycling in streams?

A

Since the water in streams move, nutrient cycling doesn’t occur in a single stationary location leading to nutrient spiralling

37
Q

What is spiraling length?

A

The length of stream required for an atom of a nutrient to complete a cycle from release into the water column to re-entry into the benthic environment

38
Q

What is nutrient retentiveness?

A

The tendency of a stream to retain nutrients
Inversely related to spiraling length

39
Q

What does a longer spiraling length indicate?

A

Low nutrient retentiveness

Nutrient availability is low because nutrients transported downstream more quickly
Nutrient atom used few times before being washed downstream

40
Q

What does a shorter spiraling length indicate?

A

High nutrient retentiveness

Nutrient availability high because nutrients transported downstream more slowly
Nutrient atom used many times before being washed downstream

41
Q

What are macroinvertebrates?

A

Consume large proportion of algae
(available nitrogen)

42
Q

What happens when there is a high abundance of macroinvertebrates?

A

Speed up the nutrient cycling in streams
-faster nutrient cycling = greater primary production
Higher nutrient retention and decrease of downstream nutrient transport

43
Q

How do pocket gophers accelerate N-cycling and redistribute N?

A

High herbivory of vegetation in a local area
Decrease the N-flux to decomposers
Fix N in their body and release it back as excretions for local plant uptake
Bring n-rich soil to the surface

44
Q

What is the effect of large grazers on terrestrial ecosystems?

A

May increase primary productivity of the ecosystem through increased rates of nutrient cycling
Heavy grazing shifts composition of plants
Without large grazers, nutrient cycling occurs more slowly

45
Q

What happens when there is a long turnover of plant biomass?

A

Nutrients remain locked up in plant biomass

46
Q

What happens when there is a short turnover of plant biomass?

A

Nutrients do not remain locked up for long

47
Q

How do humans affect the nitrogen cycle?

A

We have converted massive amounts of nitrogen from the atmosphere reservoir to terrestrial reservoirs through the use of fertilizers

48
Q

What is the Haber process?

A

Artificial nitrogen fixation
Combines N2 gas and H2 gas using a metal catalyst under high heat and pressure to form NH3

49
Q

How have we doubled the amount of fixed nitrogen per year?

A

Through combustion of fossil fuels, the Haber process, and N-fixing crops

50
Q

What are some problems caused by too much nitrogen?

A

Acid rain
Methemoglobinemia

51
Q

What is acid rain?

A

Nitrogen oxides, produced by combustion, when combined with water vapor an acid is formed

52
Q

What’s a way we are reducing the amount of acid rain?

A

The use of catalytical converters

53
Q

What is methemoglobinemia?

A

Blue baby syndrome
Nitrates in drinking water can cause hemoglobin in blood to oxidize, reducing its capacity to carry O2
Infants have low levels of methemoglobin and cannot counteract hemoglobin oxidation

54
Q

What is the human influence on carbon cycles?

A

Atmospheric CO2 over the past 1000 years shows rapid increase starting in the 1800s

55
Q

Why does deforestation increase nitrate concentrations?

A

Mainly due to soil erosion.
Ecologists created a nutrient budget for the clear-cut watershed before it was cut and found that 90% of the nutrients were tied up in the soil
After the clear-cut, nitrate moved downstream

56
Q

What can regrowing vegetation act as?

A

A nutrient sink
Young, rapidly growing understory vegetation can act as a nutrient sink after a disturbance such as forest fire

57
Q

What are problems caused by acid rain?

A

Forest dieback
Decrease of pH in aquatic and terrestrial ecosystems
Corrosion of human infrastructure
Negative impacts on human health
Acid rain can impact areas distant from the origin

58
Q

How do large grazers increase the primary productivity of the ecosystem?

A

Through increased rate of nutrient cycling

59
Q

What else does heavy grazing do?

A

Shifts composition of plants

60
Q

What would happen if we removed grazers from the ecosystem?

A

More dead plant biomass allocated to the decomposition part of the food web
Dead plant matter tends to be broken down slowly, before nutrients are returned to the soil and available to plants
Slow nutrient cycling

61
Q

What would adding grazers to the ecosystem do?

A

This means more nutrients are flowing through the main part of the food web

BIOL 208 (32 decks)

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