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BI2135: Ecology > Ecosystem Processes > Flashcards

Ecosystem Processes Flashcards

1
Q

What are the 3 subsystems of an ecosystem?

A

The herbivore subsystem, the plant subsystem and the decomposer subsystem.

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2
Q

What % of NPP is above ground in forests?

A

10%

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3
Q

What % of above ground NPP in forest enters the herbivore subsystem?

A

5%

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4
Q

What % of NPP is above ground in grassland?

A

Up to 50%

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5
Q

What % of above ground NPP in grassland enters the herbivore subsystem?

A

25%

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6
Q

What makes up humin?

A

Soil components not soluble in alkali.

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7
Q

What makes up humic acids?

A

Soil components soluble in alkali and insoluble in acid.

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8
Q

What makes up fulvic acids?

A

Soil components soluble in alkali and soluble in acid.

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9
Q

Why is humus important?

A

Acts as a nutrients pool, maintains soil structure and provides water holding capacity.

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10
Q

What are the 4 main processes in decomposition?

A

Leaching + volatilisation.
Comminution.
Non-enzymatic chemicals.
Catabolism.

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11
Q

Define leaching.

A

Water passing through/over resources and the subsequent removal of nutrients.

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12
Q

Define volatilisation.

A

The evaporation of oils, waxes and resins. Only significant in certain plant matter.

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13
Q

Define comminution.

A

The breaking up of resources into smaller parts.

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14
Q

What are some examples of non-enzymic chemical processes?

A

Cellulose oxidation by sunlight.
Weakening of chain bonds by UV.
Degradation by weak acids.

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15
Q

What organisms perform catabolism?

A

1-15% is invertebrate based; the majority is microbial.

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16
Q

How can you estimate decay rate?

A

By measuring: weight loss, density change, O2 consumption, CO2 evolution etc.

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17
Q

What factors affect decay rate?

A

Temperature.
Water regime.
Actual evapotranspiration.
Resource quality.

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18
Q

How does temperature affect decay rate?

A

Higher temperatures result in higher decay rates but there is a ceiling.

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19
Q

How does water regime affect decay rate?

A

Highest decay rate occurs when the water regime is balanced.

20
Q

How does resource quality affect decay rate?

A

Lignins + polyphenols inhibit enzyme activity. Phosphorus + nitrogen increase resource quality.

21
Q

How does the C:nutrient ratio change as decay proceeds?

A

It changes to favour nutrients - CO2 is lost as decay proceeds.

22
Q

How does nitrogen content inhibit decay?

A

High and low nitrogen content inhibit decay. High nitrogen content means microbes don’t need to decay as much litter.

23
Q

When are nitrogen and phosphorus released during decay?

A

As a result of invertebrate grazing and mycelial antagonism (conflict between fungi).

24
Q

What is the most oxidised form of carbon?

A

CO2

25
Q

What is the most reduced form of carbon?

A

CH4

26
Q

What is the most oxidised form of nitrogen?

A

NO3-

27
Q

What is the most reduced form of nitrogen?

A

NH4+

28
Q

Define annamox.

A

Oxidisation of ammonium to dinitrogen gas.

29
Q

What are nitrogenases and where are they produced?

A

Enzymes produced by cyanobacteria that reduce nitrogen to ammonia.

30
Q

What is the function of nitrate reductase?

A

To reduce NO3- to NO2-.

31
Q

Define primary productivity.

A

Rate at which biomass is produced per unit area by plants.

32
Q

Define gross primary productivity.

A

The total fixation of energy by photosynthesis.

33
Q

Define autotrophic respiration.

A

The proportion of energy fixed by photosynthesis that is lost by respiration.

34
Q

Define net primary productivity.

A

The difference between GPP and Ra - the actual rate of production of new biomass available for heterotrophic organisms.

35
Q

What are the 2 opposing processes that drive the organic carbon cycle?

A

Photosynthesis and respiration.

36
Q

Describe the latitudinal trend in primary productivity.

A

Higher latitudes have lower mean primary productivity. This somewhat reverses underground.

37
Q

Define autochthonous organic matter.

A

Organic matter produced by photosynthesis within an ecosystem’s boundaries.

38
Q

Define allochthonous organic matter.

A

Organic matter imported from outside the ecosystem.

39
Q

What is the production/biomass ratio?

A

The rapidity with which living material can replace itself.

40
Q

Define net ecosystem productivity.

A

The difference between GPP and total ecosystem respiration.

41
Q

Give examples of factors that limit productivity.

A

Inefficient use of solar energy.
Water availability.
Temperature.

42
Q

What is a constitutive plant defence?

A

A defence always present in the plant.

43
Q

What is an induced plant defence?

A

A defence produced or mobilised to where a plant has been injured.

44
Q

What is the carbon nutrient balance model (CNBM)?

A

The theory that the carbon-nutrient status of plants (determined by resource availability) controls the allocation of secondary metabolites.

45
Q

What are feeding inhibitors?

A

Compounds in plants that control decomposition rate.

46
Q

Define turnover time.

A

The period of time during which certain materials remain within a particular system.

BI2135: Ecology (15 decks)

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