Ecological succession – primary, secondary and the plagioclimax
BiologyEcology & EnvironmentAges 17–18
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Sign in to playFast-forward hundreds of years on bare rock, ground left by a retreating glacier, a coastal sand dune, an abandoned field or a burnt forest: pioneers, grasses, shrubs, pioneer trees and climax woodland replace one another, with graphs of soil depth, humus, nitrogen, species richness and biomass. Choose grazing, mowing or controlled burning to hold the community at grassland or heath (a plagioclimax); stop the management or start a wildfire to see succession resume or begin again.
Lesson: Ecological succession: primary and secondary succession, climax communities and human management
What it shows
Succession is the sequence of changes in a community over time. Each stage alters the abiotic environment, deepening soil, adding humus and nitrogen and casting shade, which makes conditions better for the next species and worse for itself. Primary succession starts where there is no soil, such as bare rock, lava, glacial till or new sand; pioneer species like lichens and marram grass tolerate the harsh conditions. Secondary succession starts where soil remains, after fire or when farmland is abandoned, so it is much faster. Grazing, mowing or burning can stop succession at grassland or heath, a plagioclimax kept for conservation.
How to use
Pick a Starting point, then press Play or drag the Year slider to watch the landscape, soil strip and six graphs. Choose Human management, its Level and Start from year, then press Stop management to let succession resume. Press Wildfire now at any year to reset the community and see secondary succession.
Parameters you can change
- Starting point Bare rock – primary, Ground left by a retreating glacier – primary, Coastal sand dune – primary, Abandoned field – secondary, Forest after a fire – secondary
- Human management None, Sheep grazing, Mowing and scrub clearance, Controlled burning
- Management level Light, Moderate, Heavy
- Management starts in year 0–400 years
Questions to explore
- Why is succession on an abandoned field so much faster than on bare rock?
- How do pioneer trees change the environment so that their own seedlings can no longer grow?
- Why must grassland nature reserves be grazed or mown every year?
