ECEC - 5 Flashcards
what are the 3 main types of permanent wetland?
1) swamp
2) bog
3) fen
Telematic wetlands is broken down into permanent and seasonal wetland, what is a seasonal wetland and what is a telematic wetland?
- marsh
- telematic wetlands = Wet terrestrial ecosystems
what is the difference between swamp, bog and fen wetlands?
swamp = inundated (flooded) for most of the year
bog and fen = not inundated or for only part of the year
what type of ecosystem is a marsh?
a transition between an aquatic and terrestrial ecosystem
what is the definition of vegetation succession?
- A gradual, directional change in the composition of vegetation
- Populations of different plant species successively replace one another
- Usually accompanied by environmental change (either causing or resulting from succession)
what does allogenic mean?
(other made) = succession driven by environmental change
what does autogenic mean?
(self-made) = succession occurs when the vegetation itself induces environmental change, creates conditions conducive to its own replacement
what is primary succession?
surfaces not previously supported by vegetation
what is secondary succession?
surfaces that have previously supported soil and vegetation
what are the 2 main processes peat accumulate through?
1) Terrestrialisation – infilling of lakes and pools with mud and peat – has occurred widely
2) Paludification – the process by which once dry land gets wetter - Increased wetness may be induced by various influences (e.g impeded drainage caused by sea-level rise, increased precipitation)
- Responsible for the development of the largest areas of wetland in Britain
what are the 2 broad types of terrestrialisation?
1) Rooting (normal) terrestrialisation – water gradually shallows by the accumulation of mud and peat – allows progressive colonisation by species more suited to shallow-water conditions
2) Rafting terrestrialisation – open water becomes overgrown directly by a buoyant mat of peat – reduces the dependency of the succession on shallowing caused by the accumulation of mud and peat
for rooting terrestrialisation what are 2 ways the mud/sediment is deposited?
Autochthonous – organic muds deposited in the original place
Allochthonous – in washed sediments
what happens if rooting terrestrialisation occurs in a swamp?
shallowing permits establishment of immersive perennials
what happens if rooting terrestrialisation occurs in a fen?
surface ceases to be inundated
what is a fen woodland?
a fen surface which becomes increasingly dry and stable
what is raised bog?
- Acidic ombrotrophic peat accumulates above the level of the fen water table
- The bog mass Sphagnum is a key peat-forming species in bogs
describe rafting terrestrialisation
- Found in small sheltered basins
- Similar to rooting
- Swamp and fen phases develop by direct colonisation of open water
- Water body fills up top – downwards
what was it initially thought caused development of blanket bog, what is it and now what is known to cause it?
- ombrogenous formation (peat) which ‘blankets’ terrain
- Initiation of blanket bog initially considered driven primarily by suitable climatic conditions (wet and cool).
- However, blanket bog can be found with Neolithic artefacts.
- Some has developed over once cultivated land (e.g. Dartmoor)
- now considered much is initiated by forest clearance
what areas of Britain was blanket bog considered to be restricted to?
– restricted to oceanic regions with wet and cool climates (e.g. much of
western and northern Britain)
- however it was seen some once developed over cultivated land
what are features of water logged environments?
- oxygen deficient (hypoxic - reduction and anoxic - completely gone)
- 02 diffusion 20,000 times slower in water than air
- 02 has low solubility in water
- affects availability of 02, NO3, Mn, Fe, S
- anoxic environment + souce of potential toxins + acidic conditions = retard normal process of decomposition
what is one of the main reasons why peat accumulates?
retarded decomposition in water logged environments
what are the 3 main adaptations of plants with lack of oxygen in the rooting zone?
1) anaerobic respiration in roots
2) transport of oxygen to roots
3) release of oxygen into the rhizosphere (soil around roots)
describe the process of anaerobic respiration in the roots?
they accumulate the less toxic malic acid rather than ethanol however its not a long term adaption to waterlogging
describe the process of transport of oxygen to the roots?
– high tissue porosity provided by aerenchyma, cavities and channels, other special oxygenating structures (pneumatophores; stilt roots)
what are ppneumatophores?
upward growing roots e.g. mangroves take air directly into rooting systems
- roots have lenticels( raised pores) which also provide support for the plant
how does the process of releasing oxygen into the rhizosphere work?
- diffusion of oxygen out of the root, enzymic oxidation on the root surface creating a small zone of aerobic conditions immediately around root
– can also oxidise phytotoxins reducing toxicity and uptake by the plant - dead stems of reed in winter may function as snorkels
oxygenation can facilitate growth of other dryland species by oxidising surrounding soil
what are the 2 waterlogging problems for plants?
1) Oxygen deficiency for underground organs
2) Increased availability of soluble phytotoxins
in soil – especially Mn, Fe and S-
what other effects can plants with high rates of radial oxygen loss have?
- can sometimes oxidise the soil sufficiently well to permit the growth of others
- May facilitate growth of more ‘dryland’ species which could otherwise not grow in wet conditions
- An example of “facilitation”
- High rates of water movement (effectively oxygenating) can also facilitate the growth of some dryland species in wetlands
