SUCCESSION Learning Objectives 1 Distinguish between primary secondary

SUCCESSION

Learning Objectives 1. Distinguish between primary, secondary and deflected succession 2. Explain what a climax community is 3. Describe an example of primary succession resulting in a climax community

Once, most of England looked like this…. .

What is succession? • Ecosystems are dynamic • This means they can and do change • Species distribution does not necessarily remain constant over a period of time • Because organisms and their environment interact, a change in one affects the other • This can happen slowly or quickly • Succession is the term used to describe these changes in species or organisms in an area, over time

Primary Succession

Examples where primary succession may occur 1. Retreating glacier 2. Sand dunes 3. Volcanic eruption and lava 4. Land subsidence 5. Silt and mud at river estuaries

Pioneer Species

Features of pioneer species • Can colonise inhospitable environments • Vast quantities of wind-dispersed seeds or spores • No dormancy ir – we a f t o N • Are photosynthetic did all the hard work! • Can fix nitrogen • Tolerate extreme conditions • Not good at competing for resources

Stages of 1 o succession • • e. g. bare rock Pioneer plants colonise, e. g. lichens Weathering of rock sand or soil Lichens die decompose Community of small plants Mosses and ferns Continued erosion + organic matter from plants thicker layer of soil • Small flowering plants, e. g. grasses • Shrubs and trees (climax)

Climax community in equilibrium • Stable state • Balanced equilibrium of species • Few, if any, new species can replace those already established • Abiotic environment less hostile • Number and variety of habitats? • Biodiversity – when does it peak? • Food webs? • Biomass?

Animals in succession • Undergo similar series of successional changes • What are these determined by? • Normally a dominant plant and animal species in climax community

Secondary succession