Disturbance and Succession:
Ecological or natural succession: When one biotic community gradually giving way to second, the second
perhaps to third, and even third to fourth, etc. This is a phenomenon of transition.
Primary succession: If an area has not been occupied previously.
Secondary succession: When area has been cleared by fire or by humans and then left alone, the
surrounding ecosystem may gradually re-invade the area, not at once, but through a series of stages.
Aquatic succession: When lakes or ponds gradually get filled and taken over surrounding terrestrial
ecosystems.
Nonequilibrium theory of ecosystem structure (changing): Given dynamic succession, if any one or more
physical factors of environment are shifted, portion of biotic community, may again be pushed into a
state of flux (flowing, changing), which certain species, that are stressed by the new condition, die out,
and other species, that are better suited to these conditions, thrive and become more abundant.
Third principle of ecosystem sustainability: The size of consumer population in ecosystems is maintained
such that overgrazing, and other forms of overuse, do not occur.
Resilience: The tendency of ecosystem to recover from disturbance, through a number of processes,
known as resilience mechanisms (e.g. succession after a fire).
Fourth principle of ecosystem sustainability: Ecosystems show resilience when subject to disturbance.
Biodiveristy of species: There is a great importance on maintaining biodiversity. The most stable
population equilibria (plural of equilibrium) are achieved by a diversity of natural species. Simple
systems, especially monocultures (one species), are inherently unstable. Most or all succession depends
on preservation of biodiversity.
Fifth principle of ecosystem sustainability: Ecosystems depend on biodiversity.