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Vegetation Succession
Sand Dunes
Plant Succession
• 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 the strand line
Blowing sand
Salty
Dry
Saltwort
Fleshy leaves store water
Deep tap roots
Low growing
Sandwort
Waxy leaves
Sea Rocket
Fleshy, waxy leaves
Tap roots
Frosted orache
‘Mealy’ leaves are salt repellant
Long tap roots
Couch grass Embryo Dune
Leaves prostrate
Withstands modest burial
Tolerates salt
SaltwortFrosted orache
Couch Grass
Embryo Dunes
Scattered
foreshore plants
Seaweed (humus)
On shore winds
Sand builds up
Highest tide line
Level of built-up sand
Frosted orache
Embryo dune
Lyme Grass
Embryo Dune
• Sand Couch and Lyme Grass
• Grow side roots laterally
• Underground Stems – rhizomes…this stabilizses the sand.
• Can tolerate occasional immersion in water.
• Sea rocket also found here.
•
Foredunes
Couch grass (salt tolerant)
Lyme grass (salt tolerant)
Marram grass
Fore Dune
• Higher humus content
• Lower salt content.
• Marram grass becomes a key plant in stablizing the dunes.
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• Deep roots anchor the
grass in the sand.• Can align with wind
direction to reduce moisture loss
Much bare sand hence ‘yellow’
Yellow dune
• Marram grass, ragwort.
• Humus and soil acidity increased.
• Marram grass suited to the conditions
• Dry conditions.
Ragwort
Marram
• Less bare sand• More humus• Lower pH• Less Marram• More ‘competitors’
Fixed (grey) dunes
Marram more sparse and weaker
Other species dominate
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
Main dune ridge
Lower relief intersects water table
Phragmites reeds
Rushes
Seasonal slack
Rushes
Creeping willow
Main dune ridge
Slack
Dune heath
Cotton grass
Final stages of succession
Alkaline shell sand
Grassland Heathland
Acid mineral sand
Dune Scrub (often spinous!)
Gorse
BuckthornDog rose
Mixed Woodland Climax
Man’s activities usually prevents this
from developing
New embryo dunes are forming….
Back on the foreshore…..
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