Sand dunes - Psammosere PDF

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Summary

Sand dunes formation...

Description

Sand dunes - Psammosere Embryo dune formation - Seeds are blown by the wind or washed in by the sea - Poor rooting conditions due to: drought, strong winds, salty sea water immersion and alkaline conditions - Wind moves sand in the dunes and allows rainwater to soak through quickly - Strong onshore winds blow sand above the high water mark and push sand inland through saltation - Lyme and marram grass grow to stabilise the sand - They are adapted to the conditions that surround the dunes - Colonising species - Adds nutrients to soil Embryo and foredune conditions - pH 7 - Poor water retention - High water mark - Low organic matter (0.1%) - Sand - alkaline - Seaweed deposits humus Embryo and foredune plants - Sandwort / saltwort - Sea rocket - Sea couch - Frosted orache - Adaptations: waxy leaves, deep tap roots, prostrate habit, high salt tolerance) Yellow dune formation - Plants trap and grow with sand, which binds sand to roots - The humus created by decaying pioneer plants creates more fertile growing conditions, and the soil becomes less alkaline as pioneer plants grow and trap rainwater - Less original plants can now grow and start to shade out the pioneers - As plants colonise the dunes, sand disappears and dunes change colour – from yellow to grey Yellow dune conditions - pH 6.5 - Organic matter = 0.23% - Reduced wind speeds as above tides - ‘Soil’ less alkaline and higher water retention - Some humus forming - Surface sand blown away, however, replenished quickly

Grey dune conditions

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Become more mature as humus and bacteria from plants and animals added to the soil Support more vegetation e.g. lichens, heaters, mosses, gorses Little mobile sand Sand no longer accumulating pH 5-6 Organic matter = 1% Higher humus content High water retention Closed vegetation community

Dune slack (plants) - Bog cotton - Flagins - Rushes - Phragmite reeds - More species associated with wetland areas Heath/moorland Climax - Water tolerant plants grow here - Slacks can occur - water table exposed - Climax community develops - Soil can support larger and more diverse vegetation...