Transcript Sand Dune Succession - Clydebank High School

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
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 Embryo Dune
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
Lyme Grass
Embryo dune
Frosted orache
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
Marram
grass
Lyme grass
(salt tolerant)
Couch grass
(salt tolerant)
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
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….