Sand dune succession is a well-studied example of primary succession, found on coasts such as Studland in Dorset. Dunes further inland are older, so walking away from the sea is like moving forward in time through the seral stages.1. Embryo dunes. Near the strandline, pioneer plants such as sea rocket and sand couch grass colonise bare sand. They tolerate salt spray, drying out and shifting sand. Their roots trap blown sand, forming small dunes.2. Yellow dunes. Marram grass becomes dominant. It grows upwards through accumulating sand, and its deep roots and rhizomes bind the sand. Its leaves roll up, reducing water loss. As it dies, humus starts to form, but the sand is still yellow because there is little humus.3. Grey dunes (fixed dunes). Further inland the sand is stable and humus darkens it. Mosses, lichens and flowering plants such as lady's bedstraw and bird's-foot trefoil grow. Bird's-foot trefoil has nitrogen-fixing bacteria in its root nodules, adding nitrates to the soil. Marram grass declines because it is outcompeted.4. Heath and scrub. The soil is deeper and holds more water. Heather, gorse and shrubs such as hawthorn grow. Rain leaches ions from the soil, making it more acidic.5. Woodland. Given enough time, pine, birch and then oak may form the climax community.
Along a transect inland, soil pH typically falls, while humus content, water retention, species diversity and plant height increase. Students often investigate this by recording percentage cover and soil properties at intervals along the transect.
Along a transect inland, soil pH typically falls, while humus content, water retention, species diversity and plant height increase. Students often investigate this by recording percentage cover and soil properties at intervals along the transect.