Answered By: Steven Profit Last Updated: Oct 18, 2016 Views: 284
Below are partial entries from The Encyclopedia of Ecology and Environmental Management, Blackwell Science.
Primary Succession is most often defined as succession occurring on substrata that either have had no previous plant cover or that contain no organic matter. There is a problem with either definition. Succession is generally regarded as ‘primary’ when it occurs on a landslide where rock and subsoil, virtually free of organic matter, are exposed, despite the fact that before the landslide was formed the substratum was just beneath a developed soil carrying vegetation. Succession is also generally regarded as ‘primary’ where it occurs on the fresh deposits of meandering rivers or accreting salt marshes or mangrove swamps, despite the fact that some remains of animals, algae and microorganisms are present in the deposits. The essential point is that primary successions start with very little organic matter in the substratum or none at all, while secondary successions start with some kind of developed soil. (more)
This is Succession occurring where there has already been a plant cover, and there is some kind of developed soil. It is contrasted with primary succession. Secondary successions may be:
1. natural, for example after fire, flood or wind-blow in forests or woodlands, or after severe Drought, or following mound-building or scratching by animals in grassland; or
2. human-induced, for example on land that is no longer cultivated, grazed, mown or burnt, or in forests that have been clear-felled and abandoned.
Regeneration of late-successional vegetation may or may not be successional in nature. Human-induced secondary successions commonly contrast with natural internal successions in involving unnatural mixtures of species recruited from various natural habitats; for example, forest edges against cliffs, rivers and mires or swamps, and from the rocks, alluvia, mires and swamps themselves (Marks 1983). They also sometimes involve species introduced from other continents, as in case of some of the prominent annuals and biennials in the oldfield successions in North America. (See this entry here.)