What is an Ecosystem? An ecosystem is a community of plants and animals and the physical environment in which they live. What are the components of an Ecosystem? Non-Living Environment Living Environment There are two main Coastal Ecosystems: (i) Sand Dunes and (ii) Salt Marshes
SUN ROCK SOIL AIR WATER ANIMALS VEGETATION How do elements of an ecosystems interact & affect each other?
What is the process of succession? Ecosystems undergo change through time and overtime the sequence of vegetation on a site changes – this is called SUCCESSION . Succession is changes in vegetation overtime in response to changing physical conditions. Ecological succession on previously un-vegetated sites, such as on sand dunes, mudflats and salt marshes is known as PRIMARY SUCCESSION.
Succession occurring in:
a Sand Dune Ecosystem – is known as a psammosere
a Salt Marsh Ecosystem – known as a halosere
Initially conditions are very harsh – only certain species survive ( pioneer species ) Over time the physical environment becomes more favourable to plant growth (with changes in soil, water availability etc.) As this occurs vegetation becomes more diverse, taller and more woody in character with an increase in biomass Eventually the Climax Community is reached (that best suited to the conditions) – often a particular tree species that becomes dominant THE PROCESS OF SUCCESSION Important – the focus of succession is CHANGE OVER TIME Back
PLANT SUCCESSION - A SUMMARY PIONEER COMMUNITY The first plants to colonise an area – e.g. in a Salt Marsh Ecosystem – halophytes such as Salicornia are the first to colonise as they can tolerate the saline environment. CLIMATIC CLIMAX (Natural Vegetation) The vegetation that is best adapted to the environment it is in (in balance with the soils and climate of the area) SERAL STAGES (temporary conditions which develop over time) PLANT SUCCESSION PRISERE (the complete chain of events from pioneer to Climax Community)
SAND DUNE SUCCESSION - PSAMMOSERES
How do Sand Dunes Develop? Sand Dunes are an important deposition feature formed by the wind (aeolian processes). They develop where: (i) There is a strong on-shore wind (ii) There is a large supply of sand (iii) There is a large inter-tidal range so that large areas of sand regularly dry out
The wind moves sand dried out at low tide inland by
Strong shear force: as wind blows over the surface
Ballistic impact: from other sand grains
2 . An obstacle (e.g. driftwood) will halt saltation and result in deposition and the accumulation of sand which will begin to pile up around the obstacle 3 . Pioneer Plants (e.g. Marram Grass) can tolerate the harsh conditions and begin to colonise the area – this breaks up the wind and encourages further deposition and growth of the dunes. The roots begin to stabilise the dune. A Simple Sequence of Sand Dune Formation and Saltation
4. Another dune forms on the seaward side of the original dune – this shelters the original dune – causing a change in the environmental conditions – other types of vegetation begin to colonise. 5 . A sequence of dunes form (oldest inland) and the environmental conditions continue to change due to the change in vegetation 6. The number and diversity of plant species on the dune increases – eventually the climax community is reached.