Sand Dunes

Question 1

What is Vegetation Succession?

Answer 1

The evolution of plant communities at a site over time - from pioneer species to climax community

Question 2

What is psammosere?

Answer 2

The name for the succession of vegetation which takes place on a sand dune.

Question 3

What are pioneer species?

Answer 3

The first plants to colonise an area of bare ground (e.g. marram grass)

Question 4

What is a climax community?

Answer 4

A community of plants which have reached a steady state. The end point of “succession” (e.g. deciduous woodland)

Question 5

What are the key ingredients necessary for dune formation?

Answer 5

• large, flat beach
• large tidal range
• plentiful supply of sand
• onshore wind
• an obstacle
• vegetation

Question 6

Why is a large,flat beach and large tidal range necessary for dune formation?

Answer 6

• exposed large amounts of sand allowing it to dry it out - must be dried out to be picked up and transported by the wind

Question 7

Why is a plentiful supply of sand necessary for dune formation?

Answer 7

Need a large accumulation of sand for dunes to form

Question 8

Why is onshore wind necessary for dune formation?

Answer 8

• blowing and transporting all sand in one direction - all sand accumulates in one place

Question 9

Why is an obstacle necessary for dune formation?

Answer 9

• gives sand something to build up around initially - sand can’t build up around itself, needs an obstacle it’s going to hit and start formation

Question 10

Why is Vegetation necessary for dune formation?

Answer 10

• acts as an anchor to the sand - supports and anchors dunes in place

Question 11

Formation of Sand Dunes Overview

Answer 11

• dunes for typically on large flat beaches where there must be a supply of sand, a means of transporting it (wind), and somewhere for it to be deposited more quickly than it’s eroded

Question 12

Formation of Sand Dunes - Stage 1 (Strandline/obstacle)

Answer 12

• dunes begin to form beyond the Strandline of the beach where sand dries out between low and high tide and debris (such as driftwood and seaweed) that collects on the beach, acts as an obstacle and sediment begins to build up

Question 13

Formation of Sand Dunes - Stage 2 (Embryo Dunes)

Answer 13

• over time, and embryo dune develops, which may become vegetated by pioneer species such as marram grass
• marram grass is adapted to the dry, salty, windy conditions of the back shore
• vegetation stabilises the dunes in two ways. Firstly, the roots bind the sand together, and secondly the above ground vegetation traps particles of sand as they are blown over the beach

Question 14

Formation of Sand Dunes - Stage 3 (yellow and fore dunes)

Answer 14

• eventually several embryo dunes will coalesce (join together) to create foredunes and yellow dunes
• these dunes have a distinctive form; the windward side is gently sloping and shaped by wind movement. The leeward side faces away from the shore and is steeper and unstable
• distinctive crest and slack formation

Question 15

Formation of Sand Dunes - Stage 4 (Grey Dunes/Slacks)

Answer 15

• grey dunes are fixed dunes which have been fully colonised by vegetation and may eventually develop into a climax community of health land or woodland
• depending on the height of the water table, areas between dunes may be damp or even contain standing water