Understanding Ecosystem Dynamics: Communities and Succession

Ecosystem Fundamentals

An ecosystem is defined as the set of living beings that inhabit an environment, the physical-chemical factors of that environment, and the interactions that develop between them.

Ecological Communities

Communities are sets of populations of different species that occur together in space and time and interact with each other.

Ecological Succession

In any ecosystem, there is a progression towards the acquisition of a series of successively more stable states, which we call succession. These sequences occur over long periods and are often irreversible, leading to ecosystem maturation. As maturation increases, the rate of ecosystem changes slows down, as more efficient regulatory mechanisms develop in relation to a situation of greater complexity.

Types of Succession

• Allogeneic Succession: Occurs when species changes result from geological, physical, and/or external chemical changes.
• Autogenic Succession: Occurs on land that has just been laid bare, without gradual changes in abiotic influences. This type is further distinguished into primary and secondary succession.

Primary Succession

Primary succession develops from bare ground, such as on newly formed lava fields or areas exposed by glacier retreat. In the latter case, the substrate is first colonized by mosses, lichens, and some shallow-rooted herbaceous species that alter soil conditions, enriching it in nitrogen.

Secondary Succession

Secondary succession occurs when vegetation has been eliminated in whole or part, but the soil remains well-developed and conserves a good number of seeds and spores.

Climax Community

Whether primary or secondary succession, the final stages tend towards a balance. This balance becomes maximal and stable if individuals that die are replaced by young of the same species. This stable community is called the climax community, and it is determined by the physical characteristics of the medium.

Ecologists consider every ecosystem perceived as being in balance with external conditions, and unable to increase its biomass, as a climax ecosystem.