Vegetation Succession Sand Dunes. Plant Succession Evolution of plant communities From pioneer...

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…..