Ecological Succession

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Succession is a key topic to understanding conservation and biodiversity. Ecological succession is the process by which an ecosystem changes over time and results in the formation of a stable community. There are two types of ecological succession, Primary and Secondary.

Primary succession:

This is when succession is started by the formation of totally new land. This may happen naturally or be caused by humans (Anthropogenic). New land is referring to a newly formed land mass such as a volcanic island. When first formed these consist of pure rocks. Plants (flora) can not live here and so no animal life (fauna) can live here. These islands are very inhospitable are identified mostly by a almost total lack of soil (see: Soils).

Over a period of time a thin layer of soil may form by the processes of weathering. Some bacteria and Lichens (Lichens) may already have already colonized the rocks by absorbing nutrients from the rocks. But it is not until this first weathering has formed the thin soil that succession really starts. At this point mosses and ferns are able to grow. These mosses and ferns dominate the area and the Lichens die.

Many of these early plants are Legumes (legumes) and this helps to fertilise the soil. When the soil becomes more fertile and thicker, due to humus (Humus) and more weathering of the Bedrock/regolith, other flora can colonize the area. As the plant life changes so does the fauna/animals that live in the area. The life present will change many times and we called these stages a seral stage (seral stage). The whole process for a particular ecosystem is known as its sere (sere).

Succession ends when a climax community is reached. A climax community is normally a forest ecosystem as trees are the most efficient at using sunlight. However in areas that have to low or to high amounts of insulation (insulation) may have different climax communities. They could be described as ecosystems that have reached the carrying capacity (carrying capacity) of their environment.

Secondary succession:

This is much the same as Primary succession except it occurs when the current seral stage (seral stage) is removed abruptly. This may be due to a natural disaster such as an earthquake or volcanic eruption, or by anthropogenic (Anthropogenic) effects such as deforestation and strip mining.

This time there is already soil and probably seeds present. This means the succession will happen more rapidly than primary succession. Wind blown plants that are tolerant to high levels of sun and grow fast called pioneer or fugitive species will colonise the area. These will then be replaced by herbaceous (herbaceous) plants, which will then be followed by bush like plants and trees if the ecosystem can support such flora.

These types of succession are known as autogenic (autogenic).

In some cases allogenic succession (allogenic succession) may occur. For example a lake may silt up (silt up) over time to eventually produce a terrestrial (terrestrial) environment. Autogenic succession may then occur on this new land.