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Ecosystem Function and Services > Ecosystem Processes > Flashcards

Ecosystem Processes Flashcards

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1
Q

What are the three types of diversity?

A

*Genetic
*Species
*Functional

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2
Q

What is genetic diversity?

A

The genetic variation within species, both geographically separate populations and individuals within single populations

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3
Q

What is species diversity?

A

Alpha (the species that exist in a sampling unit), beta (the variance between sampling units), gamma (the sum of all the species that exist in a specific area)

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4
Q

What is functional diversity?

A

The different types of functions in a community

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5
Q

What are the five big extinctions?

A

*Ordovician-Silurian Extinction = 440 mya
*Late Devonian Extinction = 364 mya
*Permian Triassic Extinction = 250 mya
*End Triassic Extinction = 200 mya
*Cretaceous-Tertiary Extinction = 65 mya

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6
Q

What are biodiversity hotspots

A

A biogeographic region with significant levels of biodiversity that is under threat from human habitation.

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7
Q

How can we measure species diversity?

A

*Species evenness
*Species richness
*Species dominance
*Diversity Indices: Shannon-Weaver Index and Simpson Index

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8
Q

Does increasing evenness cause greater diversity?

A

Yes

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9
Q

What are SADs?

A

Species rank abundance diagrams

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10
Q

What are the four formal models used to describe SADs?

A

*Geometric = least equitable distribution
*Log series = randomaly arranged
*Log-normal = intermediate curves
*Broken stick = most equitable distribution

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11
Q

What is SPACE?

A

Species-area relationships = bigger area equals more species

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12
Q

What are functional types in ecology?

A

Organisms showing similar responses to environmental conditions and having similar effects on the dominant ecosystem processes.

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13
Q

What is the Species richness-stability model?

A

When you increase richness, the stability of the function will also increase

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14
Q

What is the Rivet model?

A

Losing a few species may have minimal impact, but at a threshold, further species loss leads to a sudden collapse of ecosystem function.

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15
Q

What are the four ecosystem stability concepts?

A

*constancy - remaining unchanged
*Resistance - remaining unchanged despite disturbances
*Resilience - returning to a referential state after a disturbance
*Persistence - through time of populations

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16
Q

What is ecological collapse?

A

When an ecosystem suffers a drastic, if not permanent, reduction in organisms, it can result in mass extinction, usually precipitated by a disastrous event occurring on a short time scale

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17
Q

What is ecosystem resistance?

A

The ability of an ecosystem to respond to disturbance by resisting damage and recovering quickly

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18
Q

What is the tipping point?

A

The point at which ecosystems collapse (irreversible change) occurs

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19
Q

What causes ecosystem collapses?

A

*Natural events: asteroids, extreme weather, fire, disease, volcanic activity
*Man-made events: pollution, resource exploitation, agriculture, erosion

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20
Q

What caused the extinction of non-avian dinosaurs?

A

A 10km wide asteroid, creating a crater of 180km

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21
Q

What are the two types of tipping points?

A

*Catastrophic events, e.g., fire, draught, volcanic action
*Subtle events, e.g., climate change, pollution

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22
Q

How much of the world’s ice-free land have humans converted for agriculture and urbanisation?

A

43%

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23
Q

What are nutrients?

A

elements essential to the functioning of organisms

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24
Q

What are the four types of nutrients?

A

*Primary macronutrients
*Secondary macronutrients
*Tertiary macronutrients
*Micronutrients

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25
What are macronutrients?
The elements used in large quantities, e.g., carbon, hydrogen, Oxygen, and Nitrogen
26
What are micronutrients?
Needed in much smaller quantities, e.g., iron, magnesium, zinc
27
Under what conditions does the rate of carbon fixation control the demand for other nutrients?
Carbon fixation rate controls nutrient demand when all nutrients are freely available.
28
What does nutrient availability affect?
Primary productivity
29
What two nutrients can restrict carbon fixation?
Nitrogen and magnesium restrict the supply of chlorophyll or enzymes that catalyse carbon fixation reactions
30
What does the Gershmel model show?
Attempted to show differences between ecosystems regarding nutrients, transferred, and stored. He first considered it as a closed system.
31
What are the three things Gershmel believed the closed system consisted of?
*Biomass = Fallout pathway - flux between litter *Litter = Decay pathway - flux between soil *Soil = Uptake pathway - flux between biomass
32
What are the enviromental factors that control fluxes?
*Temperature *Light *Water
33
How does temperature control fluxes?
*Cold: deep litter layer due to slow decomposition, chemical reactions work slowly so organisms function more slowly, little vegetation due to slow growth *Warm: thin litter layer and soil due to rapid decomposition, abundant vegetation due to rapid growth
34
How does water control fluxes?
*Too much (Waterlogging): Low primary productivity due to low nutrient availability, slow decomposition due to lack of oxygen *Too little: slow or seasonal growth due to lack of water for primary producers, slow decomposition due to lack of water for decomposer organisms, temperature, and Water environmental factors meet.
35
What are four examples of ways nutrient cycles can gain from the outside?
*Weathering = Chemical elements are added to the soil from rock breakdown *Biological activity = Organisms like plants, bacteria, and fungi release chemicals such as organic acids *Precipitation and Dry Deposition = dust storms, atmospheric pollution *Agriculture = fertilisers
36
What are the two types of weathering?
*Physical = thermal expansion and wedging *Chemical = caused by oxygen, acids, and water
37
What are examples of ways nutrient cycles can lose nutrients?
*Runoff and leaching = floods, overland flow, flow through soil *Agroecosystems = human remove nutrients
38
What is the equation for Net Primary Productivity?
NPP = GPP – Respiration (R)
39
How do you measure plant gas exchange?
IRGA, which is an infra-red gas analyser
40
What is NEP?
Net ecosystem production.
41
What is the definition of NEP?
Describes the carbon balance of an ecosystem. For an ecosystem to be sustainable, NEP cannot be negative
42
How do we measure NEP?
*Directly by sequential biomass sampling *Indirectly with chambers *Directly with eddy covariance, measures over any land surface
43
What does photosynthesis effect?
The amount of evapotranspiration
44
What happens to photosynthesis during drier conditions?
It reduces photosynthesis by limiting carbon dioxide uptake through stomatal closure and by directly damaging the photosynthetic machinery within the plant.
45
What is an eddy covariance tower?
A meteorological instrument equipped with sensors to continuously measure the turbulent fluxes of gases (like carbon dioxide, water vapor, and methane) and energy between the Earth's surface and the atmosphere.
46
What is decomposition?
The breakdown of material, ultimately to CO2 of biologically derived origin, with the involvement of other substances and processes.
47
What is the main process of decomposition?
The bulk of organic material undergoes an enzymatic oxidation, this process is called respiration.
48
What is mineralisation?
The overall process of conversion of an element from organic to inorganic form as a result of microbial decomposition
49
What is immobilisation?
Conversion of an element from the inorganic to organic form in microbial tissues, thus rendering the element unavailable to plants.
50
What are the four breakdown mechanisms?
*Physical: fragmentation by: wet-dry, shrink-swell, hot-cold, animals, physical abrasion, leaching *Physico-chemical: oxidation by various means including photo-oxidation (generates free radicals which may attack a variety of molecules, although these are often only restricted to the surface of opaque materials) *Chemical: hydrolysis by acids, whether biotically created or abiotically, fragments and other metabolites may recombine by condensation reactions to give more stable compounds in the soil *Biological: ingestion and digestion but purely extracellular until small molecules, extracellular enzyme activity, oxidation
51
What are the primary sources of organic matter that contribute to litter?
Plant residues (Roots and shoots), fecal materials (livestock manures, sewage sludge), and animals.
52
What is a key characteristic of litter composition?
Litter is comprised of varying proportions of different organic compounds.
53
How does the breakdown of different organic compounds in litter interact within the soil?
Their breakdown interacts in various ways, involving the interactions and release between different soil pools.
54
What factor can lead to low decomposition rates in organic matter?
Decomposition rates can be low if the availability of Nitrogen in organic matter is low. The carbon to nitrogen ratio is a good indicator of the relative decay rate.
55
What is photo-oxidation?
A chemical process where a material is oxidized (loses electrons) through the combined action of light and oxygen.
56
How can substrates differ at a molecular level?
Substrates may have different molecular sizes, solubilities, and chemical constitutions.
57
What might need to happen to larger molecules before they can be used in cellular metabolism?
Other molecules may need to be depolymerised or reduced in molecular size to enter into cellular metabolism.
58
What are the challenges associated with the breakdown of cellulose, hemicellulose, and lignin/lignin-like molecules?
May be high molecular weight and intermixed so that their breakdown is complex, their surface availability may be restricted by other substrates within a solid matrix. Thus their breakdown rates may be slow, and in the case of lignin, partial.
59
What is the potential energy contribution of lignin breakdown to microorganisms?
Lignin breakdown may contribute little energy to a microorganism (fungi). Lignin breakdown may be a rate-limiting step, its fragments and similar molecules then may condense to form and accumulate new soil organic matter.
60
How does the composition of different plant parts influence decomposition?
Different plant parts contain quite different amounts of sugars, celluloses, hemicellulose, and lignin (and other substances).
61
In ecosystems, which organisms achieve most of the OM breakdown?
Microorganisms, .e.g., fungi are the most rapid to colonize into substrates using their hyphae to penetrate and enter the substrates
62
What are the two types of fungi involved in decomposition?
Basidiomycota and Ascomycota
63
From which group of fungi are the main categories of breakdown borrowed?
The main categories of breakdown are borrowed from the wood-degrading fungal types comprising the white rot, brown rot, and soft rot types.
64
What are white-rot fungi characterised by?
Their ability to rapidly and completely decompose lignin. This requires energy, usually by co-metabolism of sugar molecules from hemicellulose and cellulose breakdown. It is an aerobic process.
65
What are brown rot and soft rot fungi characterised by?
They slowly and partially decay lignin in order to get the macromolecules. This destabilises the lignin mechanically and chemically alters it.
66
How can temperature influence decomposition?
Temperature affects microbial activity rates. Global warming, the greening of the tundra, and the loss of ancient soil organic matter are examples of temperature-related changes.
67
How does moisture content in the soil impact decomposition?
Moisture affects water availability for microbial activity and the aerobic status of the soil (influenced by drainage and plowing).
68
What are some effects of low soil pH on decomposition and soil organisms?
Low pH reduces microbial activity, as microorganisms have optimal pH ranges. It can also lead to the solubilization of heavy metals like Aluminum and result in a lack of earthworms.
69
What is occlusion?
The physical protection of organic matter within soil aggregates or bound to mineral surfaces, which can slow down decomposition.
70
How does the size of organic matter particles affect their decomposition?
The size of particles influences the surface area available for microbial attack and thus affects decomposition rates. Smaller particles generally have a larger surface area to volume ratio, potentially leading to faster initial decomposition.
71
How can air availability impact decomposition?
Aeration status, ploughing, and drainage
72
What is the primary purpose of the Tea Bag Index (TBI)?
To measure the decomposition rate of organic matter in different environments.
73
What two types of commercially available tea bags are typically used in the TBI?
Green tea (representing easily decomposable compounds) and rooibos tea (representing more recalcitrant compounds).
74
What is the TBI process?
Known weights of green and rooibos tea bags are buried at a specific depth for a set period, then retrieved, cleaned, dried, and re-weighed to determine weight loss.
75
What does a higher stabilization factor (S) indicate about the decomposition process in a given environment?
A higher S indicates that a larger fraction of the organic matter is not easily decomposed, suggesting slower overall decomposition.
76

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