Ecology trip Flashcards
Where do sand dunes form?
above the intertidal zone where specialised plants trap sand and build dunes over time
When does sand dune formation begin?
when the tidal actions give rise to accretion of sands enclosed areas of the seashore either:
- directly in front of the existing shore or
- further out below the low tide line, often associated with the presence of a promontory (causing slowing of tidal currents)
What does wind action cause?
it causes dry sand deposition around emergent colonising plants (that slow windspeed) called Foreshore colonisers
Types of foreshore colonisers
- Cakile maritima (sea rocket)
- Atriplex spp (Orache)
- Salsola Kali (saltwort)
When does the first dune ridge appear?
appears as more sand is trapped by foredune colonisers
Types of foredune colonisers
- Elymus farctus (sand couch grass)
- Leymus arenarius (lyme grass)
- Ammophilia arenaria (marram grass)
- Honkenya peploides (sea sandwort)
What happens at the front of the dune system?
further tidal deposition of sand at foreshore leads to the appearance of a new dune ridge called foredune
What does the original dune become and what is it dominated by?
the original dune becomes a fixed dune ridge behind the foredune dominated by:
- Ammophilia arenaria (marram grass)
- Euphorbia paralis (sea spurge)
- Senecio jacobea (ragwort)
- Triplerospermum maritimum (mayweed)
- Taraxacum officinale (dandelion)
What happens as dunes age?
as they age and new foredunes form, older dunes change in their structure and vegetation
When dunes age to become the second fixed ridge, what species appear?
- Festura rubra (red fescue)
- Viola spp. (violets)
- Plantago martima (plantain)
- Lotus corniculatus (birdsfoot trefoil)
- Trifolium arvense (hare’s foot clover)
- Rhinathus minor (yellow rattle) hemiparasitic on other plants
Succession on sand dunes : primary succession
- the original first dune ridges are gradually pushed further inland in the succession
- soil organic matter and organic nutrients begin to increase
- the slightly acid nature of rainfall causes soil to become less alkaline
- fungi and bacteria become more widespread
What woody species appear in primary succession?
- Rosa spinosissima (Burnett’s rose)
- Salix repens (creeping willow)
Mature dunes/dune slacks develop between the older dune ridges are characterised by? what plants are present?
they are characterised by damp neutral soil and the presence of
- Alnus glutinosa (alder)
- Salix repens (creeping willow)
What is a mature dune system characterised by?
a range of different habitats of different ages
- generally lower fertility and water retention compared to terrestrial habitats
- occasional large mammals: hare, badger, fox, especially on coastal dunes rather than dune islands
What are the two ways spatial variation arises?
- succession: a dynamic process, giving rise to continuous localised change over time
- zonation: a form of stasis, where localised differences are permanent
Zonations occurs…
where two markedly different habitats converge e.g. the seashore
- at either extreme, characteristic species of each habitat predominate
- zonation between habitats tends to be stable
The intermediate zone
- usually has very few of the characteristic species
- often contains several uniquely adapted species
- spatial location may change
- this zone rarely changes into a new habitat
The intertidal zone
- aka the littoral zone is where land and sea meet, between high and low tides
- rich in nutrients and oxygen
- have hard (rocky shores) or soft (sandy, muddy shores) substrata and are influenced by factors like tidal range, slope and exposure
When are seashore organisms exposed to air?
when the tide goes out
- due to tide coming in and going out 2x a day, organisms at the top of the shore are exposed to air more often than those at the bottom
- resulting in a vertical zonation
What is the main reason for vertical zonation?
the varying ability of the organisms to withstand desiccation when the tide is out
