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Succession   Definitions
 

Succession Definitions

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Brief overview of A2 Succession AQA

Brief overview of A2 Succession AQA

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    Succession   Definitions Succession Definitions Presentation Transcript

    • ECOLOGICAL SUCCESSION the orderly progression of a vegetation community, through a series of developmental stages, reaching equilibrium in a climax community.
    • Volcanic island
    • Forest fires in Australia
    • Abandoned parking area
    • Glacial retreat/moraine
    • Pioneer Species bare ground conditions favour pioneer plant species. Species which grow best where there is little competition for space and resources. (moss) moss are low growing, carpeting the ground and with little height. Mosses are unable to successfully compete for space amongst taller, dense ground cover. often have light seeds, which are easily transported by the wind. seeds which rapidly germinate and do not require dormancy. grow quickly, reproducing themselves before slow other slower- colonising species arrive to out compete them. often ‘opportunist’ species which are able to rapidly exploit a sudden new opening in ground plant cover.
    • QUICK QUESTION How would bare ground which has just started to be colonised by pioneer species differ after 2 years in: competition, soil structure, ground temperature and nutrient levels?
    • In the process of succession, the species present in an area will gradually change. Bare ground Two years later No plant competition for light, space, nutrients or water. Intense plant competition for space and other resources. Soil mobile and liable to erosion and loss. Soil bound by roots and plant cover A more extreme surface microclimate because the bare The plant cover provides a certain amount of ground soil both absorbs and reflects heat more than soil covered insulation from extremes of temperature. There are now in vegetation also a variety of microclimates within the vegetation. A drier environment because there is no plant cover to Plant cover and increasing humus levels help to retain hold moisture above ground and little humus to hold it in water. the soil. Lower nutrient levels in the soil. The nutrient levels in the soil will have increased.
    • environmental conditions on the same patch of ground are very different to the conditions when the first pioneers arrived. a variety of longer-lived, slower colonisers have displaced many of the species in the early pioneer community. plants are not the only colonisers. Herbivorous invertebrates which feed on those particular plant species have arrived. These then attract a range of carnivorous invertebrates to feed on them. larger herbivores such as rabbits and deer will also graze this area. the soil will be enriched as the dung is recycled by the dung-dwelling community. the simple food chains of the earliest pioneer stage, when few species were present, have developed into more complex foodwebs.        many, if not all of the environmental changes have been brought about by the communities living there. During the processes of living, growing and reproducing, species interact with and modify their habitat.  in 2 years, the biodiversity (variety of life) on the bare patch of ground has soared, as it has been colonised by fungi, plants and animals. The ecosystem has developed from a very simple one with few interactions, to a much more complex system with a staggering number of interactions going on between individuals, species and the habitat itself.  
    • Climax Community If left undisturbed, the area will pass through a number of further different successional stages, each with its own characteristic mix of species. All of n these different successional stages are known as a collectively as a sere. Each new community will be better adapted to the the changed environment which has been provided provided by the by the previous community. Eventually, a climax or ‘final’ community is reached. At reached. At this point, succession will not er further. Climax community is in a stable equilibrium with prevailing climate. Abiotic factors such as climate determine dominant species of that community. In the UK, this is most likely to be deciduous oak woodland.
    • Primary Succession is found on a new land surface or in water and various seral stages are passed through before climatic climax is reached. It is an orderly sequence of events where one community is replaced by another. Biomass is created via decomposition and provides more nutrients for the soil allowing for greater and variety of plants and animals to exist at each successive seral stage:
    • Secondary Succession if succession is halted before reaching dynamic equilibrium a secondary succession occurs. Interruptions include fire, disease, climate change and deforestation. more rapid - spores and seeds remain in soil. does not begin with pioneer species, but one of the subsequent successional stages. land alteration will mean some of the species in the climax community will be different.
    • Polyclimax If sub-climax is due to local variations in soil etc.
    • Plagioclimax If sub-climax is a consequence of human activity. Management practices of humans (burning, clearing and grazing of land, urban and transport developments).
    • Hydrosere Succession which starts in fresh water. A wetland, which is a transitional area between open freshwater and dry land, provides a good example of this and is an excellent place to see several stages of a hydrosere at the same time.
    • Halosere Succession which starts in salt water. A salt marsh
    • Lithosere Succession which starts on newly exposed rock surface. Examples, one left bare as a result of glacial retreat or volcanic eruptions.
    • Psammosere Succession which starts on sand surface. Sand dunes