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

Saltwort Frosted 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

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 GrasslandHeathland Acid mineral sand

Dune Scrub (often spinous!) Gorse Buckthorn Dog rose

Mixed Woodland Climax Man’s activities usually prevents this from developing

New embryo dunes are forming…. Back on the foreshore…..