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The Seashore

Sand Dunes

Fixed (grey) Dune

When sand is mobile and accretion significant marram growth is actually stimulated by sand-burial and this pioneer species dominates. Unfortunately marram sows the seeds of its own downfall, behind the main fore dune ridge (created and stabilised by marram) wind speeds decrease and so does accretion. This favours the growth of other species, especially red fescue grass (Festuca rubra), and marram begins to die out.

Now we have a stable or fixed dune community and the biodiversity increases as the abiotic factors that were so extreme in the mobile dunes ameliorate. Water retention of the substrate increases, nutrient status of the ‘soil’ improves and the impact of salt spray and wind scour decrease.

The nature of the fixed dune community is extremely variable depending on the pH of the substrate and activities of grazing animals, especially rabbits.

If there is a lot of shell sand present the conditions will be alkaline and a diverse community of species will develop

Click the link to go to alkaline grey dune

If there is little shell sand present the conditions will be acidic and a community of fewer species will develop

Click the link to go to acid grey dune

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