Succession Flashcards
Define succession
the directional change in community structure and composition over time
Define primary succession
the colonisation of previously unvegetated areas (e.g. post-glaciation, volcanic eruption)
Define secondary succession
the colonisation of previously vegetation areas (e.g. after a fire, abandonment of an agricultural field)
What factors effect a disturbance regime?
intensity, frequency, and spatial extent of a disturbance
Give an example of a large-scale catastrophic disturbance
Crown fire in Yellowstone park 1988
Give an example of a less severe disturbance
ice storm (large extent but low intensity) and windthrows (trees breaking)
Give an example of rocky shore succession
bare rock - bacteria - green seaweed - limpets/periwinkles - brown seaweed
Describe Frederic Clements’ concept of a ‘superorganism’
studying a plant community as an organic entity - growing, maturing and dying as if it is a single organism, consider species interactions most important
Describe Henry Allen Gleason’s ‘individualistic’ concept of succession
the dynamics of a community can only be understood as the sum of the dynamics of the component species, consider change events and environmental conditions most important
Describe an experiment which provided evidence against Clement’s superorganism concept
Robert Whittaker showed that theres gradual change in species composition as elevation increases
What 2 hypotheses did Frank Egler propose in 1954 related to predicting succession?
that there is relay floristics (similar to clement’s idea of a climax community) and an initial floristic composition
Give an example of testing the intermediate disturbance hypothesis
(Sousa) Observing dominance of algae on boulders of varying sizes - smaller boulders are disturbed most frequenty, so fewer are dominate by Ulva compared to medium sized boulders, which have the most species on average. Large boulders are disturbed least frequently, with few species dominated by dominant Gigartina.
