Sand Dune Succession

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Transcript Sand Dune Succession

Vegetation Succession
Sand Dunes
V A VANNET
Plant Succession
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Evolution of plant communities
From pioneer species to climax vegetation
Related to change in the environment
Change brought about by the plants themselves
This change then favours new species
‘Plants are the architects of their own demise’
Sand Dune Transect
The Foreshore
Salty
Blowing sand
Dry
Saltwort
Fleshy leaves store water
Low growing
Deep tap roots
Sandwort
Waxy leaves
Sea Rocket
Fleshy, waxy leaves
Tap roots
Frosted orache
Long tap roots
‘Mealy’ leaves are salt repellant
Couch grass
Withstands modest burial
Leaves prostrate
Tolerates salt
Frosted orache
Saltwort
Couch Grass
Embryo Dunes
Highest
tide line
Scattered
foreshore
plants
On shore
winds
Seaweed
(humus)
Sand
builds up
Level of built-up sand
Embryo dune
Frosted orache
Foredunes
Lyme grass
(salt tolerant)
Couch grass
(salt tolerant)
Mobile (yellow) dunes
Marram grass
Marram grass
• Cannot tolerate salt
• ‘Thrives’ on being
buried by sand
• Inrolled leaves
• Long tap roots
• Underground
rhizomes stabilise
dunes
Much bare sand
hence ‘yellow’
Ragwort
Marram
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Less bare sand
More humus
Lower pH
Less Marram
More ‘competitors’
Fixed (grey) dunes
Other species dominate
Marram more sparse
and weaker
Increasing floristic diversity
Harebells
Bedstraw
Restharrow
Parasol mushrooms
More humus and soil moisture
Why ‘grey’?
Lichens
Marram now very sparse
Ground cover almost complete
Dune slacks
Lower relief
intersects
water table
Main dune ridge
Phragmites
reeds
Rushes
Seasonal slack
Creeping willow
Rushes
Main dune ridge
Slack
Dune heath
Cotton grass
Final stages of succession
Grassland
Alkaline shell sand
Acid mineral sand
Heathland
Dune Scrub (often spinous!)
Buckthorn
Dog rose
Gorse
Mixed Woodland Climax
Man’s activities
usually prevents this
from developing
Back on the foreshore…..
New embryo dunes
are forming….