Psammosere
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In geography, a psammosere is a sand sere - an environment of sand substratum on which ecological succession occurs. Most common psammoseres are sand dune systems.
In a typical succession on a sea-coast psammosere, the organisms closest to the sea will be salt tolerant species such as littoral algae and glasswort. Progressing inland the succession is likely to include meadow grass, sea purslane, and sea lavender eventually grading into a typical non-maritime terrestrial eco-system. Psammoseres graduate until they reach a climatic climax which ultimately leads to the growth of oak trees. As you move away from the high water mark there are many characteristic features that change and help you determine the natural succession of the dunes. For instance, the saturation rate slows down as you move inland from the HWM as the land is more compact and has better soils rather than sand which is seen at the start of the dune formation. The land is less acidic with closeness to the climatic climax as there are fewer shell pieces in the soil. The shell pieces are slightly acidic[citation needed] and prevent any substantial vegetation growth. As the quality of the soil improves and it has a more neutral pH it provides the foundation for increased growth and instead of basic marram grasses and heather there are ample conditions for such trees as birch and ash to survive.
In an idealised coastal psammosere model, at the seaward edge of the sand dune the pH of the soil is typically alkaline/neutral with a pH of 7.0/8.0 particularly where shell fragments provide a significant component of the sand. Tracking inland across the dunes a podsol develops with a pH of 5.0/ 4.0 followed by mature podsols at the climax with a pH of 3.5 - 4.5.
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