Dune Succession Jinshan

Succession The evolution of plant communities at a site over time - from pioneer species to climax vegetation At each stage of the succession the plant community alters the soil and microclimate, allowing the establishment of another group of species One community of plants is therefore replaced by another as the succession develops Eventually a climax community is reached where the vegetation is in a state of equilibrium with the environment and there is no further influx of new species

Dune names

Embryo Dunes Smallest of the dunes and the youngest Closest to the sea Little or no vegetation due to frequent inundation by the sea

Fore Dune Pioneer stage of succession Called pioneer stage as pioneer plants start the succession process Species such as sand couch grass. Lyme-grass and Marram grass are salt tolerant which allows them to grow so close to the sea Pioneer species help to start to stabalise the dunes

Yellow Dune This dune is bigger than the fore dune Marram grass dominates due to its fast growing ability and deep root system Other species sand sedge, sea holly and portland spurge Called the yellow dune as vegetation is patchy and you can see patches of yellow sand

Grey Dune Dunes now have almost continuous plant cover Developing humus layer from decaying vegetation helps to retain moisture Called grey dune due to developing soil layer (although very thin) Marram grass ends here and other colonizing species such as gorse, braken and heather

Climax vegetation No new species added when you reach this stage and community stays stable for long periods Vegetation said to be in equilibrium with the environment The noticeable increase in biodiversity levels off

Equilibrium Once the ecosystem reaches climax vegetation, the dune system is said to be in a steady state equilibrium. Before this it is said to be developing over time and maintained by stabilizing negative feedback loops. What does it mean to be developing over time? What do you think are the negative feedback loops in this system? What evidence would you expect to see in a system that has the characteristics of developing and one which has reached steady state equilibrium?

Plan an IA!! In pairs, brainstorm what characteristics of a dune system you could measure to see if there was evidence of succession taking place. Think about how you might go about measuring each characteristic

Virtual field trip - Jinshan We are going to walk along a dune system taking note of the changing vegetation with increasing distance from the sea. You should make a note of the following: Distance from sea % vegetation cover Number of plant species Soil pH reading Soil colour

A transect along a dune system pH reading: 7.8 0m

10m – sea couch pH reading: 7.8

20m marram grass pH reading 7.6

30m pH reading 7.5

40m pH reading 7.0

50m pH reading 6.9

60m – sea spurge pH reading; 6.5

70m red fesue pH reading: 6.0

80m moss, bracken pH reading: 5.5

90m - gorse pH reading: 5.0

100m – thistles, brambles, trees pH reading: 4.8

Dune profile measurements Distance 3 6 9 12 15 18 21 24 Height 0.5 1 2 4 7 27 30 33 36 39 42 45 48 51 8 10 16 54 57 60 63 66 69 72 75 78 19 17 13 81 84 87 90 93 96 99 102 5

Data presentation Using the data you have collected draw four graphs and then evaluate your findings: A graph to show how vegetation cover changes with increasing distance from the sea A graph to show how the types and number of species changes with distance from the sea A graph to show changes in soil pH readings A graph to show the dune profile Q. Is there any evidence of succession? Negative feedback loops or a developing steady state equilibrium?