Succession dynamic ecosystems Succession is the gradual directional change of a community over time

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Succession dynamic ecosystems Succession is the gradual directional change of a community over time Slide 2 There are two types of succession: Primary successionSecondary succession Here the starting point is bare ground Here a community is damaged and the soil is left plants then colonise (e.g. a woodland has been felled). The END POINT of both types of succession is the climax community Slide 3 Succession on sand dunes Nearest the sea, only a few species can colonise the sand. Why? Sand constantly moves High salt concentration freely draining soil soil has a low nutrient status Slide 4 Succession on sand dunes Very specialised species live in this area, they are called PIONEERS These species are show xeromorphic & halophytic characteristics Sea rocket (Cakile maritima) Sea holly (Eryngium maritimum) Slide 5 Sea holly.. pioneer species Latin name: Eryngium maritimum of sand dunes Slide 6 These PIONEER species give way to other species as you move in land Couch grass (Agropyron junceiforme) This species has widespread roots, this helps in two ways Stabilise the substrate Absorb all available water Slide 7 The quality of the substrate improves in two ways as you move back through the dunes 1. Nutrient levels increase 2.Water retention improves This is due to: Death & decay of animals Decay of seaweed Decay of plant material A skeletal soil begins to develop Slide 8 These species further improve the edaphic conditions This makes the substrate more hospitable, encouraging other species. Marram grass (Ammophila arenaria) These species are still XEROPHYTIC Slide 9 Marram grass (Ammophila arenaria) Large network of roots, leading to dune developement Marram produces shoots along its stem, ensuring that it is never covered with sand This can lead to large sand dune systems Slide 10 Dunes at this stage are called yellow reflecting how little organic matter the substrate contains The substrate will turn to grey as the levels of dead material increases Slide 11 The species to follow next in the succession, are N fixers Restharrow (Ononis repens) Birds foot trefoil (Lotus corniculatus) These add N to the soil Slide 12 As Nitrogen levels increase, other species become more common A common one is Red Fescue (Festuca rubra) These species stabilise the substrate further Slide 13 http://bcs.whfreeman.com/thelifewire/conte nt/chp55/55020.html http://ecoplexity.org/node/219 www.youtube.com/watch?v=vNHnwHaSol Awww.youtube.com/watch?v=vNHnwHaSol A

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