Vegetation Succession

1
Vegetation Succession
Sand Dunes
V A VANNET
2
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

3
Sand Dune Transect
4
The Foreshore
Salty
Blowing sand
Dry
5
Saltwort
Fleshy leaves store water
Low growing
Deep tap roots
6
Sandwort
Waxy leaves
7
Sea Rocket
Fleshy, waxy leaves
Tap roots
8
Frosted orache
Long tap roots
Mealy leaves are salt repellant
9
Couch grass
Withstands modest burial
Leaves prostrate
Tolerates salt
10
Saltwort
Frosted orache
Couch Grass
11
Embryo Dunes
Highest tide line
On shore winds
Scattered foreshore plants
Seaweed (humus)
Sand builds up
12
Level of built-up sand
13
Embryo dune
Frosted orache
14
Foredunes
Lyme grass (salt tolerant)
Couch grass (salt tolerant)
15
Mobile (yellow) dunes
Marram grass
16
Marram grass

• Cannot tolerate salt
• Thrives on being buried by sand
• Inrolled leaves
• Long tap roots
• Underground rhizomes stabilise dunes

17
Much bare sand hence yellow
18
Ragwort
Marram
19

• Less bare sand
• More humus
• Lower pH
• Less Marram
• More competitors

20
Fixed (grey) dunes
Other species dominate
Marram more sparse and weaker
21
Increasing floristic diversity
Harebells
Restharrow
Bedstraw
22
Parasol mushrooms
More humus and soil moisture
23
Why grey?
Lichens
24
Marram now very sparse
Ground cover almost complete
25
Dune slacks
Lower relief intersects water table
Main dune ridge
26
Phragmites reeds
27
Rushes
28
Seasonal slack
Creeping willow
Rushes
29
Main dune ridge
Slack
Cotton grass
Dune heath
30
Final stages of succession
Grassland
Heathland
Alkaline shell sand
Acid mineral sand
31
Dune Scrub (often spinous!)
Buckthorn
Dog rose
Gorse
32
Mixed Woodland Climax
Mans activities usually prevents this from
developing
33
Back on the foreshore..
New embryo dunes are forming.