Ecological succession explained
After bare substrate forms or an established community is disturbed, organisms colonize, persist, replace one another, or coexist. Soil, seed banks, dead wood, nearby source populations, herbivores, fire severity, and chance can send similar sites along different trajectories rather than one predetermined ladder.
Scope: A worldwide overview of community change after new substrate, disturbance, or abandonment, emphasizing terrestrial examples and fire. Succession is presented as contingent assembly shaped by surviving legacies, dispersal, interactions, climate, and repeated disturbance—not a universal march through fixed stages toward one permanent climax. · Last updated
Primary and secondary are starting conditions
Primary succession is used for surfaces such as fresh lava or newly exposed sediment where soil and biological legacies are initially limited. Secondary succession follows disturbance of a previously occupied site and may retain soil, roots, microbes, seeds, standing trees, or dead wood. The boundary is useful but not perfect: disturbances vary continuously in severity, and different patches within one event can retain very different legacies. [1][2]
Arrival and interaction shape each trajectory
Colonists must reach a site, establish, and interact with residents. Early organisms can facilitate later arrivals by building soil or shade, inhibit them by monopolizing space, or simply tolerate them while environmental conditions change. Priority effects mean that arrival order can matter. Consequently, two nearby sites with similar climate may diverge because they retained different survivors or received different propagules. [1][4]
Fire does not always start the clock at zero
Fire effects depend on intensity, severity, season, fuel pattern, and the adaptations of local species. Some plants resprout from protected tissues, some seeds respond to heat or smoke, and surviving patches provide recolonists. In Yellowstone and other fire-adapted landscapes, post-fire mosaics create varied conditions rather than uniform devastation. Calling every burn a return to bare ground erases those living and physical legacies. [2][3][4]
There is rarely one final community
Older accounts often pictured succession as a fixed sequence ending in a stable climax. Modern evidence supports multiple pathways and continuing change: drought, browsing, invasive species, pathogens, climate trends, and repeated disturbance can alter direction or hold a site in a persistent state. Researchers describe trajectories with long-term plots, ages, soils, and historical evidence rather than assuming that a mature-looking forest is the inevitable endpoint. [1][3]
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Source-checked editorial guide. Last updated . This guide teaches identification and field skills; it is not a substitute for expert verification when it matters.
