successional

Successional is an adjective relating to succession, the gradual process by which the species composition and structure of an ecological community change over time. Successional dynamics typically follow a disturbance or the creation of new habitat, leading to a series of commonly recognized stages from early pioneers to later, more stable communities.

Ecological succession is often categorized as primary or secondary. Primary succession occurs on sites where no soil or organisms previously existed, such as newly formed lava flows or retreating glaciers. Secondary succession follows disturbance that leaves the soil intact, such as fire, logging, or agricultural abandonment. Within these broad categories, communities pass through stages that may include pioneer species, mid-successional assemblages, and late- or climax-successional communities, though exact trajectories vary by system and context.

The mechanisms driving successional change include facilitation, where early species modify the environment to aid later ones; inhibition, where existing vegetation hampers new arrivals; and tolerance, where later species tolerate limited resources until competition shifts. Competing ecological models—historically the deterministic, progress-oriented view of a climactic endpoint and the more contingent, niche-based perspective—recognize that multiple trajectories are possible, and disturbances can alter or reset successional progress.

In applied contexts, successional concepts guide restoration and land-management efforts. Managers may aim to steer ecosystems toward a desired successional stage, use active interventions to accelerate or slow progression, or rely on natural succession as a low-maintenance pathway. The study of successional patterns also employs tools such as chronosequences, which compare sites of different ages to infer temporal dynamics.