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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 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….