SECONDARY SUCCESSION: CHARACTERISTICS AND EXAMPLES - BIOLOGY - 2025

A secondary succession is a type of ecological succession that has to do with the “recolonization” of a habitat after a major disturbance, natural or artificial, leaves it partially devoid of life.

Like primary successions, a secondary succession is an orderly and directional process that involves changes in a community over time; changes by means of which one community replaces another sequentially, until a new, completely stable one is established.

Secondary succession after a deforestation event. Grasses first colonized the space and later trees (Source: Tomasz Kuran aka Meteor2017 / CC BY-SA (http://creativecommons.org/licenses/by-sa/3.0/), via Wikimedia Commons)

However, this type of succession is distinguished from primary successions in that biological communities develop in sites where there are already pre-existing communities, that is, where the disturbance did not completely remove living nutrients from the environment.

Let us remember that primary successions almost always have to do with the colonization of natural environments that have been subjected to ecological disturbances that eliminate all forms of life in them.

In some scenarios, it could be said that a secondary succession is that phenomenon that follows a primary succession in cases of catastrophic ecological disturbances, although this is not usually true for disturbing events that are not followed by prior colonization of "simple" species..

Therefore, some secondary successions do not imply a prior primary succession and the study of these is very important for the understanding of many ecosystem dynamics.

Characteristics of the secondary succession

Secondary successions are responsible for most of the ecological changes in an ecosystem, since many biological communities are permanently in a state of secondary succession, since it is the replacement of a community established by different sets of animals and plants.

- It is a gradual process through which a community seeks to reach its "climax", that is, its most stable situation

- They can occur with or without the prior existence of a natural or artificial disturbance of the ecosystem

- In cases where such disturbances occur, secondary successions occur in strict dependence on the severity of these

- They also depend on the type and frequency of disturbance faced by an ecosystem, in addition to some abiotic and biotic factors

- They are faster processes than primary successions, since they do not merit the deposition of soil or organic nutrients in the substrate, but directly from the colonization of new species, either by dispersal of spores, eggs or seeds, etc.

- The establishment of one species and not another depends both on the dispersal limitations inherent to these and on the nutritional status of the substrates. That is, the composition of the species in a community that is established by secondary succession always depends on the type of environment in question.

- The assembly of the new communities depends, in turn, on the size of the habitat

- Some authors consider that secondary successions are the result of interspecific competitions between "pioneer" species and "late" species

- The stages of a secondary succession are similar to those of a primary succession, since in this one it is also found that a “pioneer” species colonizes the new environment and provides a “base” from which the new community can be formed.

- Generally, insects and grasses from adjacent ecosystems are the first to colonize the “cleared” area

- These first species are replaced by animals and plants with more complex needs and habits and this will happen as many times as necessary for the species composition to “stabilize”, as long as the area is not disturbed again.

Examples of secondary sequences

Some authors consider that secondary successions correspond to the events by which an ecosystem "revives itself" after a portion of it has been destroyed, either by a natural or artificial event (caused by man).

Examples of secondary succession events could include:

- The renewal of a forest after a fire, as long as the fire does not destroy the ecosystem in such a way that no trace of life remains

This succession occurs thanks to the fact that many seeds and roots of the trees in a forest remain on the ground or are buried in it and, once the disturbance stops (ceases), they can germinate and grow, causing the ecosystem to eventually return. to its initial state.

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Plants that regenerate in this way have a better chance of survival, since they do not initially compete with other plants, neither for resources nor for exposure to the sun's rays.

- The settlement of more complex life forms after a primary succession

When an ecosystem suffers some type of catastrophic disturbance, that is, when all living beings in an ecosystem are eliminated by some natural or artificial event of great magnitude, initially a primary succession occurs.

Primary successions consist of the settlement of species with few ecological requirements, usually autotrophic microorganisms, fungi, algae and mosses. These species tend to "prepare" the substrate for slightly more complex species, such as grasses, ferns, insects and other invertebrates.

The presence of such "primary" life forms further conditions the substrate of the ecosystem, allowing the colonization of secondary pioneer species, with much more complex requirements and behaviors.

These species are usually medium-sized (eventually large) shrubs and trees, small mammals, and a wide range of different animals. Pollinators and seed dispersers such as birds and a huge number of insects have a prominent participation.

Secondary successions are considered by many ecologists to be the "restoration" of an ecosystem to the closest shape to what the ecosystem was before the disturbance, and this involves different time scales for each particular site.

- Renewal of an ecosystem after a disease

A secondary succession can also occur in the context of illness. In this sense, we can consider a plant ecosystem in which a community of plants is affected by a bacterial or viral pathogen, for example.

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The negative effects of a disease can cause the total or partial death of members of the community, but they do not always imply the destruction of the soil or roots.

Therefore, the subsequent growth of plants that died, either by germination of their seeds or by activation of their roots, may signify a secondary succession event.

References

1. Chang, CC, & Turner, BL (2019). Ecological succession in a changing world. Journal of Ecology, 107 (2), 503-509.
2. Guevara, S., Purata, SE, & Van der Maarel, E. (1986). The role of remnant forest trees in tropical secondary succession. Vegetatio, 66 (2), 77-84.
3. Horn, HS (1974). The ecology of secondary succession. Annual review of ecology and systematics, 5 (1), 25-37.
4. Johnson, EA, & Miyanishi, K. (2010). Disturbance and succession. Plant disturbance ecology: the process and the response, 1-10.
5. Pandolfi, JM (2008). Succession.
6. Walker, LR, & Del Moral, R. (2003). Primary succession and ecosystem rehabilitation. Cambridge University Press.