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Coastal Environments Processes and Management > 6: Mangroves > Flashcards

6: Mangroves Flashcards

1
Q

What are 4 adaptations of mangrove vegetation that makes them suitable mangrove environments?

A

1 root structure

  1. breathable roots
  2. vivipary and proagule seed dispersal
  3. Salinity tolerance
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2
Q

What are vivipary and propague seeds? How does this aid their survival and dominance in mangrove environments?

A

They are seeds that have started to grow before they disperse from the plant . This means that they can stick to the ground once they fall which gives them greater resistance against tides so they can get a foothold and they can also root quickly in to the ground once this has happened as they are already fairly matured

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3
Q

Where are mangroves located usually and outline the Australian difference?

A

They are typically located in the tropics but in Australia they strangely stretch further towards the poles.

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4
Q

Where did mangrove species first derive from? What happened once they left this area?

A

Central Pacific - once the species dispersed further from this area either East or West they developed in to two very dissimilar species

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5
Q

What was the name of mangrove species that dispersed west?

A

Indo-West Pacific

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6
Q

What was the name of the mangrove species that dispersed east?

A

Atlantic East Pacific

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7
Q

Which area has the highest diversity/concentration of mangrove species?

A

Indonesia

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8
Q

What happens to mangrove species diversity with latitude?

A

Decreases

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9
Q

Why is the mangrove species diversity in the south hemisphere much greater?

A

Because there is more ocean and less land

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10
Q

What is the limit of the southern hemisphere mangrove distribution and why?

A

Corner Islet, after this is the Bass Strait which features too cold water temperatures

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11
Q

What forms in mangroves and why?

A

Zones of different species due to different tolerances of salinity, fluidity and oxygen concentrations

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12
Q

What distinguishes mangroves in N. Australia?

A

They are usually a lot thicker and taller at the front when it progrades outwards and forward

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13
Q

How to describe saltmarshes in relation to mangroves and why?

A

Cousins - they are usually found in more temperate regions (e.g. Tasmania)

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14
Q

What are the rough 6 zones of mangrove zonation?

A

Bare mudflats, seaward amrgins, Rhizophora, Transition, Tidal Flat, Salt Flat

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15
Q

What allows the identification of different mangroves’ zones?

A

Compiling images of mangroves at highest 10% of high tides and lowest 10% of low tides. This enables identification of composites from which spectral signature can be inferred and used to define the vegetation and therefore zones of the mangrove

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16
Q

What is the role of tides in mangrove environments?

A

Bring sediment/material to the mangroves at high tide. When at high tide and following the retreat of the tide line they deposit the material at high tide

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17
Q

What effect does the sedimentation at high tide have upon the mangrove environment?

A

Progradation at upper sections of the mangrove and relative subsiding of the lower sections of the mangrove.

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18
Q

What are the 8 physical factors that affect the development of mangroves over time, in order of bigger to smaller timescales of operation?

A 
Tectonism
Eustatic sea level
Ocean circulation
Steric sea level
channel migration
floods and storms
waterbody mixing
tides
19
Q

What are the 7 biological factors that affect the development of mangroves over time, in order of bigger to smaller timescales of operation?

A 
Evolution
Mangrove life history
competition
epidemic disease
propagule viability
Organism interactions
Microorganisms
20
Q

What spatial factors affect the distribution of species in mangrove environments?

A

Dominance of freshwater/saltwater

Differing amount of fluvial/marine deposition

21
Q

Outline the likely mangrove setting in lagoon environments?

A

Lagoons do not have an inlet and so the tidal range is limited. This also means that the substrate is thinner as there is no repeat pattern of deposition. This simple environment also means there is likely to be homogeneous vegetation

22
Q

Outline the likely mangrove setting in fringe environments

A

Opposite to lagoon. They have a good access to tidal variation and so the supply of sediment to the substrate is fairly consistent meaning the mangroves become fairly strong

23
Q

Outline the likely mangrove setting in island environments

A

They are basically to exposed to the coastal tidal variation because of their low elevation and so the mangroves are overwhelmed meaning they cannot develop well

24
Q

Which area was found to have a set of additional unique factors affecting the distribution/environment of mangroves?

A

Australia

25
Q

What affected mangroves at the (1) global scale; (2) environmental setting; (3) hydrology and topography?

A

global scale = temperature
environmental setting = geomorphic type
hydrology and topography = ecology

26
Q

What were the 3 scales that Colin proposed for affecting mangrove environment and associated factors to these scales?

A 
Macro = climate and sea level change
Meso = Hydrodyanmics and sedimetn supply
Micro = Geomorphic processes and biologic processes
27
Q

What were some examples of things in the macro scale for things affecting mangrove environments?

A

Climate = temperature, precipitation and storms

Sea level = SLR and subsidence

28
Q

What were some examples of things in the meso scale for things affecting mangrove environments?

A

Hydrodyanmics = inundation and salinity

Sediment supply = inorganic and organic material

29
Q

What were some examples of things in the micro scale for things affecting mangrove environments?

A

Geomorphic processes = accretion, nutrient addition, autocompaction, shrink/swell
Biological = above-ground biomass production, below-ground biomass production, decomposition

30
Q

What is the tidal frame?

A

The difference betweent eh highest astronomical tide and the mean neap tide in relation to occupation over the substrate (vertically or translated laterally)

31
Q

What section of the tidal frame is usually occupied by mangroves?

A

Half plus a bit extra towards inland (this half is usually the more inland section from just before the highest astronomical tide mark and a bit before the mean sea level mark

32
Q

What is the name given to the area that the mangrove environments occupy?

A

Available accommodation space

33
Q

What is the total accommodation space?

A

Where material/sediment is deposited from the influence of tides (this includes the available accommodation space)

34
Q

What makes the total accommodation space so suitable for mangrove environments as opposed to just the underlying substrate?

A

The realised accommodation space is composed of sediment that is softer which is easier for mangroves species to occupt

35
Q

What is the realised accommodation space?

A

The area where vegetation can grow and because the deposited material is softer it increases the available accommodation space

36
Q

What happens to the available accommodation space with the knowledge that the tides have deposited softer substrate? What does this mean for vegetation on mangroves?

A

It gets bigger and so the vegetation can now grow further out towards the sea

37
Q

What happens to the tidal frame and therefore all the different accommodation space categories in light of sea level rise?

A

Vertical range of the tidal frame shifts upwards. This causes the accommodation spaces to shift or extend further inland depending upon the condition of the realised accommodation space (deposited material above the substrate_

38
Q

What happens to the state of the realised accommodation space due to SLR and why?

A

It extends further inland and this then also means that it receives more organic material due to vegetation life cycles

39
Q

What are the 8 ways that the available accommodation space can increase due to SLR?

A 
Eustatic SLR
Deep subsidence
Tectonism
Hydrological changes along estuaries
Organic matter decomposition
Root zone collapse
Substrate compaction or consolidation
40
Q

What happened to sea level around Australia around 8 and 6 ka?

A

At 8ka it started to rise slightly and then by 6ka it stabilised a bit but then continued to rise abit

41
Q

What happened to mangroves in Australia in light of the sea level changes that took place?

A

At 8ka the sea level is not high enough and so there is no sediment and therefore no suitable mangrove environments. But then at 6ka it has risen sufficiently so that sedimentation can occur. Mangroves start to occur as vegetation is supported. But SLR is too much and so eventually the sedimentation becomes too much as well resulting in the many mangroves becoming uplifted too much to form floodplains. Mangroves are forced to the interior of valleys.

42
Q

What has enabled us to see how the environment changed its sedimentation rate and therefore species changed from those seen in mangroves to floodplains? Which paper was this found in btw and which area does it apply to?

A

Sediment cores. Woodroffe et al. (1985) in Northern Australia

43
Q

What happens to vegetation at the three stages of SLR in northern Australia? (in Woodroffe et al. 1985)

A

Firstly there is a lot of low elevation species (Rhizophora) then species diversification occurs as SLR due to Rhizophora being outcompeted in a range of environments that are not all ideally suitable to that species. As sedimentation continues the mangrove retreats back to the shoreline as more inland areas are no longer inundated by tides as they are too high. Instead saline flats form behind the mangrove

Coastal Environments Processes and Management (14 decks)

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