Vegetation and coast stabilisation Flashcards
How are sand dunes made?
Wind blown sand stabilised by plant succession
What is the first stage of plant succession?
Bare ground is gradually colonised by plants called ‘pioneer species’
What is the second stage of plant succession?
Pioneer species modify the environment by binding sand or mud with their roots and add nutrients when they die and decay
What is the third stage of plant succession?
Creeping plants with leaves keep moisture in the sand/ mud, these changes allow other species to colonise
What is the fourth stage of plant succession?
The new plants modify the environment by providing shade and improving the soil
What is the fifth stage of plant succession?
As the environment changes, different species colonise until it becomes stable
What is the sixth stage of plant succession?
The final community to colonise is the climatic climax community (trees)
Describe embryo dunes
Small scattered patches of marram grass which are largely self-seeded or growing from rhizomes up to 3m long. Only pioneer species can cope with the adverse conditions
Describe mobile (yellow) dunes
Some large areas are bare, moving sand but greater cover of marram grass
Describe semi-fixed (grey) dunes
Smaller patches of bare sand tinted grey with many plants besides marram grass
Describe fixed dunes
Almost complete vegetation cover, marram grass is sparse in isolated clumps before ultimately disappearing whilst many other species are present
Describe dune slacks
Sand becomes eroded so the water table can be reached so forms a damp depression prone to flooding in the winter. Large numbers of rabbits keep the vegetation short but cause damage in blow-outs where bare sand is exposed
Describe climax
Sand dunes generally develop into shrub and then woodland
What are halophytes?
Plants that can tolerate saline (salty) conditions
What are salt marshes?
Areas of flat, silty sediments that accumulate around estuaries or lagoons
Where do salt marshes develop?
- In sheltered areas where deposition occurs
- Where salt and fresh water meets
- Where there are no strong tides or currents to prevent deposition or accumulation
As mudflats develop (1) tolerant plants such as eelgrass begin to colonise and (2) the land. Halophytes such as (3) slow down (4) to trap more mud and silt. As sediment accumulates the surface becomes (5) and (6) start to colonise
Salt Stabilise Codgrass Tidal flow Drier Different plants/ sea asters
What are creeks?
Created by water flowing across the estuary at low tide to divide up the salt marshes
