Practice question

Secondary succession occurs where a community previously existed and a disturbance removes organisms without eliminating all soil and biological legacies. Forest regrowth after fire, abandoned agriculture, storm damage, or logging are common examples. Remaining seed banks, roots, spores, microbes, soil structure, and nutrients accelerate recovery compared with primary succession. Primary succession starts on newly exposed or sterilized substrate with little or no developed soil, as on fresh lava, glacial till, or bare rock. “Autogenic” and “allogenic” describe causes of successional change rather than whether prior life existed. Autogenic change is produced by organisms themselves, such as shading or soil modification; allogenic change is driven by external forces such as sediment deposition or climate. Either type of driver can influence a secondary sequence. The retained ecological memory is the tested distinction: because the site formerly supported life, colonists do not need to build an ecosystem entirely from mineral substrate. This usually makes secondary recovery faster, although severe disturbance, isolation, or invasive species can redirect it.