ECOLOGICAL SUCCESSION: TYPES, STUDIES AND EXAMPLES - BIOLOGY - 2025

Ecological succession is the process of gradual substitution of plant and animal species in a community, which causes changes in its composition. We could also define it as a pattern of colonization and extinction in a certain place by multiple species. This pattern is characterized by being non-seasonal, directional and continuous.

Ecological succession is typical of communities controlled by “dominance”, that is, those in which some species are competitively superior to others.

Figure 1. Primary succession. Source: By Rcole17, via Wikimedia Commons

In this process, an "opening" is produced as a result of a disturbance, which can be seen as a clearing in the forest, a new island, a dune, among others. This opening is initially occupied by an "initial colonizer", who is displaced over time because he cannot maintain his presence in the place.

Disturbances usually give rise to the appearance of a sequence of species (entering and leaving the scene), which can even be predicted.

For example, early species in a succession are known to be good colonizers, grow and reproduce rapidly, while later species (which enter later) are slower in growth and reproduction, and tolerate less resource availability.

The latter can grow to maturity in the presence of the early species, but eventually end up excluding them due to competition.

Types of succession

Ecologists have distinguished two types of succession, namely: primary succession (occurring in sites without pre-existing vegetation), and secondary succession (occurring in sites with established vegetation).

A distinction is also often made between autogenous succession, which is driven by processes that operate within a particular location, and allogeneic succession, which is driven by factors external to that location.

Primary succession

Primary succession is the process of colonization of species in a place that does not have pre-existing vegetation.

It occurs in sterile inorganic substrates generated by sources of disturbance such as volcanism, glaciation, among others. Examples of such substrates could be: lava flows and pumice stone plains, newly formed sand dunes, craters caused by a meteor impact, moraines and exposed substrates after the retreat of a glacier, among others.

Figure 2. Lava flows are colonized once they cool down in the first step of an ecological succession. Source: By Jim D. Griggs, HVO (USGS) staff photographer http://pubs.usgs.gov/dds/dds-80/, Public Domain, https://commons.wikimedia.org/w/index.php? curid = 326880

During primary succession, species can arrive from distant locations.

The process of succession usually occurs slowly, because it is necessary for the first settlers to transform the environment, making it more favorable for the establishment of other species.

For example, soil formation requires the decomposition of rocks to occur initially, the accumulation of dead organic material, and subsequently the gradual establishment of soil microorganisms.

Secondary succession

Secondary succession occurs in sites with established vegetation. This occurs after a disturbance disrupts the dynamics of the established community, without completely eliminating all individuals.

Among the common causes of disturbance that can lead to a secondary succession, we can mention: storms, fires, diseases, logging, mining, agricultural clearing, among others.

For example, in cases in which the vegetation in an area has been partially or completely eliminated, with the soil, seeds and well-developed spores remaining in good condition, the process of colonization of new species is called secondary succession.

Ecological succession studies

Henry Chandler Cowles

One of the first to recognize succession as an ecological phenomenon was Henry Chandler Cowles (1899), who studied dune communities of various ages on Lake Michigan (USA), making inferences about successional patterns.

Cowles observed that the further one got from the lake shore, the older dunes were found with dominance of different plant species among them.

Subsequently, deep controversies arose in the scientific field regarding the concept of succession. One of the best known controversies has been that of the scientists Frederick Clements and Henry Gleason.

The Clements-Gleason controversy

Clements suggested that an ecological community is a superorganism, where species interact and support each other, even altruistically. In this dynamic, there is therefore a pattern of community development.

This researcher introduced concepts such as "beings" and the "climax community". The beings represented intermediate stages in the succession, while the climax was the stable state that was reached at the end of the succession process. The different climax states were the product of the numerous environmental regimes.

For his part, Gleason defended the hypothesis that communities simply developed as a consequence of the responses of each species to a series of physiological restrictions, specific to each particular location.

For Gleason the increase or decrease of a species in a community did not depend on the associations with other species.

This individualistic view of community development sees it simply as a collection of species whose individual physiological requirements allow them to exploit a particular place.

Who was right?

In the short term, Clements' vision was widely accepted in the scientific community, however, in the long term, Gleason's ideas have appeared to be more accurate in describing the process of plant succession.

Ecologists such as Whittaker, Egler, and Odum have participated in this discussion that has resurfaced throughout the development of community ecology.

Today, more recent models such as those of Drury and Nisbet (1973), and those of Connell and Slatyer (1977), are added to this discussion, contributing new visions to the old debate.

As is often the case in these cases, it is most likely that neither of the visions (neither Clements', nor Gleason's) is entirely wrong, and both are somewhat true.

How are ecological successions studied?

Successions that develop into new outcrops of land (for example an island emerged by volcanism) typically take hundreds of years. On the other hand, the lifespan of a researcher is limited to a few decades. So it is interesting to ask yourself the question of how to approach the investigation of successions.

One of the ways that has been found to study successions has been the search for analogous processes that take shorter times.

For example, the study of surfaces of certain walls in rocky coastlines, which can become bare and be repopulated by colonizing species after periods of years or decades.

Chronoseries or Substitution of Space for Time (SFT)

It is called chronoserie (from the Greek khronos: time) or "substitution of space for time" (SFT for its acronym in English), to another form commonly used in the study of successions. This consists of the analysis of communities of different ages and spatial locations, arising from a single disturbance event.

The main advantage of the SFT is that long observation periods (hundreds of years) are not required to study a sequence. However, one of its limitations implies not being able to know exactly how similar the specific locations of the studied communities are.

Effects attributable to the age of the places could then be confused with effects of other variables associated with the locations of the communities.

Examples of the study of successions

Use of a chronoseries in the study of a primary succession

An example of a chronoseries is found in the works of Kamijo and his collaborators (2002), who were able to infer a primary succession in the basaltic volcanic flows of Miyake-jima island in Japan.

These researchers studied a known chronosequence of different volcanic eruptions dated 16, 37, 125, and more than 800 years old.

In the 16-year-old stream, they found that the soil was very sparse, lacked nitrogen, and vegetation was almost absent, except for a few small alders (Alnus sieboldiana).

In contrast, in the oldest plots, they recorded 113 taxa, including ferns, herbaceous perennials, lianas, and trees.

Figure 3. The Castanopsis sieboldii tree is a representative of terminal succession in temperate forests on volcanic islands in Japan. Source:

They then reconstructed the process of succession that occurred, stating that in the first place the nitrogen-fixing alder colonized the naked volcanic lava, facilitating the subsequent entry of the cherry tree (Prunus speciosa), of medium succession, and the laurel (Machilus thunbergii), of late succession. Later a shady mixed forest was formed, dominated by the genera Alnus and Prunus.

Finally, the researchers suggested that the replacement of Machilus by the Shii (Castanopsis sieboldii) long-lived tree occurred, and in whose wood the well-known Shii-take fungus usually develops.

Study of secondary successions

Secondary successions are frequently studied making use of cultivated fields that have been abandoned. In the USA many studies of this type have been carried out, because the exact date on which these fields were abandoned is known.

For example, the well-known ecologist David Tilman has found in his studies that there is a typical sequence in the successions that occur in these old fields:

1. Annual weeds first colonize the field.
2. Perennial herbaceous plants follow.
3. Later trees of early succession are incorporated.
4. Lastly, late succession trees such as conifers and hardwoods enter.

Tilman finds that the nitrogen content in the soil increases as the succession progresses. This result has been confirmed by other studies conducted in abandoned rice fields in China.

Is there always succession?

We have argued from the beginning of this article that ecological succession is typical of communities controlled by "dominance", but it is not always this way.

There are other types of communities that are called "controlled by the founders." In this type of communities, a large number of species are present that are equivalent as primary colonizers of an opening created by a disturbance.

These are species well adapted to the abiotic environment resulting from disturbance and can hold their place until death, since they are not competitively displaced by another species.

In these cases, chance is the factor that defines the species that predominate in a community after a disturbance, depending on which species can reach the opening generated first.

References

1. Ashmole, NP, Oromí, P., Ashmole, MJ and Martín, JL (1992). Primary faunal succession in volcanic terrain: lava and cave studies on the Canary Islands. Biological Journal of the Linnean Society, 46 (1-2), 207–234. doi: 10.1111 / j.1095-8312.1992.tb00861.x
2. Banet AI and Trexler JC (2013). Space-for-Time Substitution Works in Everglades Ecological Forecasting Models. PLoS ONE 8 (11): e81025. doi: 10.1371 / journal.pone.0081025
3. Kamijo, T., Kitayama, K., Sugawara, A., Urushimichi, S. and Sasai, K. (2002). Primary succession of the warm-temperate broad-leaved forest on a volcanic island, Miyake-jima, Japan. Folia Geobotanica, 37 (1), 71–91. doi: 10.1007 / bf02803192
4. Maggi, E., Bertocci, I., Vaselli, S. and Benedetti-Cecchi, L. (2011). Connell and Slatyer's models of succession in the biodiversity era. Ecology, 92: 1399-1406. doi: 10.1890 / 10-1323.1
5. Pickett STA (1989). Space-for-Time Substitution as an Alternative to Long-Term Studies. In: Likens GE (eds) Long-Term Studies in Ecology. Springer, New York, NY.
6. Poli Marchese, E and Grillo, M. (2000). Primary succession on lava flows on Mt. Etna. Acta Phytogeographica Suecica. 85. 61-70.