Succession Flashcards
What is succession
The process by which an ecosystem gradually changes over time, biotic conditions change as the abiotic conditions change
What is primary succession
Happens on land that’s been newly formed or exposed eg where a volcano has erupted to form a new rock surface of sea levels dropped exposing a new area of land so no soil or organic material to start with
What is secondary succession
Happens on land that’s been cleared of all plants but where soil remains eg after a forest fire/deforestation
What is a pioneer species
First species to colonise an area, must be specially adapted to cope with harsh conditions
Steps involved in primary succession
-starts when a species colonise a new land surface eg seeds and spores blown in by wind and begin to grow(pioneer species)
-abiotic conditions are hostile eg no soil to retain water so only pioneer species able to grow as they’re specially adapted to cope with harsh conditions and break up the rock eg marram grass can grow on sand dunes as deep roots can get to water and tolerate salty environment
-pioneer species change the abiotic conditions as when they die microorganisms decompose their dead organic material(humus) forming a basic soil
-makes conditions less hostile eg basic soil helps to retain water meaning new organisms with different adaptations can move in and grow and these die and decompose adding more organic material so soil deeper and richer in minerals so larger plants like shrubs can grow in deeper soil which now retains even more water
-some new species may change environ so less suitable for prev species eg sand sedge stabilises sand through growth of underground stems making it less suitable for marram grass which needs constant sand reburial
Steps involved in secondary succession
-happens in same way as primary but as already a soil layer succession starts at a later stage meaning pioneer species are larger plants
-at each stage dif species better adapted for improved conditions move in and out-compete species already there so become dominant species in ecosystem
What is the final stage of succession
Climax community-when ecosystem supporting the largest and most complex community of plants and animals it can so in steady state
What is the climatic climax and example
The name for climax community for a particular climax eg in temperate climate as plenty of water and mild temps large trees grow however in polar not much water and low temps so shrubs grow instead as soil not deep and mineral rich enough
What is a plagioclimax and example
What climax community is called when succession is stopped artificially eg regularly mown grassy field won’t develop shrubs and trees
