What is succession? The series of predicable changes that occur in community over time.
· Changes cause older inhabitants to gradually die out and new organisms to move in causing more change.
Primary succession: the colonization of surfaces where no soil exists.
Examples: volcanic eruptions, lava flows, silt deposits, bare rock exposed when glaciers melt.
· First colonized by a pioneer species, usually a lichen (a combination of a fungus and an algae).
· As the lichens grow they break up the rock into soil.
· As the lichens die, they add nutrients and organic material to the soil.
· Other less hardy species can begin to colonize the area such as mosses, grasses, weeds and shrubs.
· The area finally reaches a mature, stable community that does not undergo further succession called the climax community.
· The type of climax community is usually dependant on the climate of the area.
· Climate is determined by the average precipitation and average temperature.
· Examples of climax communities are tropical rain forests, temperate grasslands, boreal forests, temperate forests or tundra.
Secondary succession: the colonization of a community after a disturbance of some kind changes the community without removing the soil.
Examples: forest fires, hurricanes, tornados, farming a field, floods
· After a disaster, the community will usually return to the original climax community unless there is a change in climate or the introduction of a non-native new species. Standard B1.40
· Sometimes random, unpredictable events may influence the path of succession.