Ecological succession

Ecological succession is a process of change in the species structure of an ecological community over time. The time scale can be decades (for example, after a wildfire), or even millions of years after a mass extinction.

The community begins with relatively few pioneering plants and animals and develops through increasing complexity until it becomes stable or self-perpetuating as a climax community. The "engine" of succession, the cause of ecosystem change, is the impact of established species upon their own environments. A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment.

Types of Succession

Ecological succession can be of two different types: primary and secondary. Each refers to a different starting point.

• Primary succession occurs in essentially lifeless areas—regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier.
• Secondary succession occurs in areas where a community that previously existed has been removed; it is typified by smaller-scale disturbances that do not eliminate all life and nutrients from the environment.

Factors Influencing Succession

Several factors can influence ecological succession: life history traits, competition, environmental conditions, and disturbance.

• Life history traits are the characteristics of an organism that affect its rate of reproduction. Traits that affect the rate of development of a species, the number of offspring the species produces, the age at which the species begins to reproduce, and the lifespan of the species can all influence the rate at which ecological succession occurs.
• Competition is a major factor controlling the distribution and abundance of species. In many cases, competition between species for resources can determine which species survive and which are eliminated.
• Environmental conditions such as climate, soil type, the amount and frequency of rainfall, and the availability of light can all affect the rate at which succession occurs.
• Disturbance is a temporary change in environmental conditions that causes a pronounced change in an ecosystem. Disturbances can have profound immediate effects on ecosystems and can, accordingly, greatly alter the natural community.

See Also

• Climax community
• Pioneer species
• Ecological disturbance
• Ecosystem

References

Ecological succession Resources
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