Sand dunes

Question 1

How does an embryo dune form?

Answer 1

Plants growing at the back of the beach cause the wind to drop locally.
Sand carried by the wind falls at these points and begins to build small sand piles
This forms another more substantial wind break, encouraging more and more sand to be deposited.

Question 2

pH of an embryo dune?

Answer 2

Highly alkaline pH values(over 8) from the calcium carbonate in shell fragments

Question 3

How tall are embryo dunes?

Answer 3

No higher than a metre

Question 4

What species live in embryo dunes?

Answer 4

Sea twitch grass, sea rocket, sea couch grass

Question 5

How do plants in the embryo dune help develop?

Answer 5

They are salt tolerant. The stabilise the dune and decay to provide humus for plants in the next stage

Question 6

How do fore dunes form?

Answer 6

Embryo dunes that persist are colonised by sea couch grass and sea holly. The join together in a line to develop into fore dunes

Question 7

How are conditions more favourable in fore dunes?

Answer 7

Lower alkalinity as levels of calcium carbonate fall. Grass from the previous stage decomposed and formed humus

Question 8

How are plants in the fore dune adapted?

Answer 8

They are drought resistant. They can withstand burial by shifting sand and high salinity levels

Question 9

What helps fore dunes reach 5 metres?

Answer 9

Plants grow and trap more sand. The root system of Marram grass stabilises the dune

Question 10

What vegetation exists in yellow dunes?

Answer 10

Mostly marran grass. Others are mosses, lichens, sea holly and sea spurge

Question 11

How tall are yellow dunes?

Answer 11

5-10 metres

Question 12

Vegetation cover of grey dunes

Answer 12

Vegetation cover is almost 100% as moss and lichens fill spaces between plants while small shrubs such as brambles appear for the first time
- Humus darkens surface layers and a true soil forms

Question 13

What is less common on grey dunes?

Answer 13

Marram grass as less sand is blown on the dune and there is competition from other plants

Question 14

What plant takes advantage of the acidic soil in grey dunes?

Answer 14

Heathers

Question 15

How tall are grey dunes?

Answer 15

10 metres

Question 16

What is a dune slack?

Answer 16

They are found in between grey dunes and mature dunes where the water table reaches the surface and causes seasonal waterlogging and surface water

Question 17

What plants live in dune slacks?

Answer 17

Cotton grass, creeping willow

Question 18

How far away are mature dunes from the shore?

Answer 18

700 metres

Question 19

How is the water content and humus in mature dunes different than in grey dunes?

Answer 19

Much higher water content here. It is very low in grey dunes. More humus. Plants here succeed previous vegetation

Question 20

What plants are supported by the soil that develops on mature dunes?

Answer 20

Shrubs and trees including hawthorn.

Question 21

Salinity of embryo dunes

Answer 21

High salinity from frequent immersion in seawater

Question 22

Why is there a lack of nutrients in embryo dunes?

Answer 22

There is no humus

Question 23

What causes a lot of salt spray on embryo dunes?

Answer 23

High wind speeds

Question 24

Why is there rapid drainage on embryo dunes?

Answer 24

Sand doesn’t hold water well

Question 25

Salinity of fore dunes

Answer 25

Still high

Question 26

Alkalinity of yellow dune

Answer 26

Slighly alkaline

Question 27

How is the soil enriched in a yellow dune?

Answer 27

Droppings from rabbits and other small mammals

Question 28

Vegetation in a yellow dune

Answer 28

Greater plant diversity - 80% of sand surface is vegetated

Question 29

Why do yellow dunes have more nutrients?

Answer 29

A humus layer builds up from dead and decomposed plants. It traps water and nutrients

Question 30

Salinity of yellow dunes

Answer 30

Lower salinity

Question 31

Nature of soil in a grey dune

Answer 31

A true soil forms as humus darkens the surface layers