Ecological succession

Under succession (Latin succedere " move up ", " follow " ) is understood in ecology and botany which ( based on natural factors ) temporal sequence of plant or animal communities ( biocenosis ) at one location. This gradual development of leads from a disturbed or altered initial stage, in extreme cases, the vegetation-free soil ( " initial stage " ) through various stages to a climax community. In colloquial language are areas which have been used earlier and left since then for a longer period itself, referred to as succession areas. Succession is then often equated with bush encroachment.

Expiration

A succession takes place in all ecosystems. The starting point is newly created (eg exposed rock surfaces, fresh sand dunes), impaired ( eg forests after forest fire or storm damage) or used (eg meadows, heaths ) habitats. But also in natural habitats can occur succession when to change the living conditions (eg climate change ). Follows the community as in this case passive gradually changing environmental conditions, one also speaks of allogenic succession. The community itself represents a significant cause and a drive for the rest of succession dar. Established communities such location factors can change themselves, eg by soil formation ( pedogenesis ) or the silt of a lake caused by dead plant litter of reed species. Newly added species can facilitate the colonization of other species, or they may displace ( by competition ).

The understanding of the succession can be, for example, in landscape planning and nature conservation apply when it comes to the disturbed balance of nature - as the basis of life for the people - to restore and secure the long term.

The assumption of a ( single ) Ecological balance to which ecosystems would develop towards after interference by succession, was placed in ecology by empirical studies in question and is of recent models and dynamic multiple equilibria given way.

Regressive succession

In addition to the above-described "normal " (or " progressive" ) succession to a highly organized " climax community ", it may even, in exceptional cases come to a backward " regressive " succession, in the highly developed communities through a simple structured to be replaced. This is for example the case when, after a forest destruction (eg after forest fire ) the ground has been so disrupted or eroded that development then takes place in a completely different direction and not the initial state, but a simple structured community (such as a bush or a rock Heide) follows.

Succession ( botany )

In botany can be distinguished:

• "Primary" Succession: This is an on newly created, nonliving habitats.
• "Secondary" Succession: The starting point is already populated and altered by the occurring species habitats here. These may be existing vegetation inventories, such as succession from meadow to forest near abandonment. But even in barren locations ground developments are here already expired (eg organic matter content, nutrient enrichment) and in the soil is usually a seed bank ( seed bank ) available.

In the case of succession to unbewachsenem ground following sequence is typical:

Initial stage, consequential stages, climax

In the initial stage of pioneer species develop the unpopulated area. Is it arose due to a disturbance by humans or due to human use, one also speaks of substitute communities. Types of such pioneering companies must have effective mechanisms for remote distribution feature (eg wind spread seeds). Often they have unlike types of Klimaxgesellschaften a greater tolerance to extreme location factors. In the initial stage and in early stages of succession species prevail with high reproductive potential, r- strategists (named after the reproduction factor r in the logistic equation ) before. r- strategists reproduce rapidly and in large numbers. Over time, migrate further species that spread slowly and displace the most competitive weak pioneer species. The pioneer species also change the location factors, such as through the accumulation (accumulation ) of nitrogen, other nutrients and humus, change water balance and climate, the impact on soil (see pedogenesis ) and on the fauna ( all the animal species).

Due to the change in location factors are now again in other species able to colonize the altered habitat. These types are more demanding (climate, water, nutrients, etc.) and have higher productivity. In consequence stages, therefore, the K- strategists put more and more ( named after the habitat capacity K in the logistic equation ) by. K- strategists proliferate less, so they have fewer offspring. However, these have a higher assertiveness in survival and displace the pioneer species. The new species in turn change the location factors, and the process goes on, a next, more demanding and more productive society accepts the regiment.

The climax is reached when the species composition no longer or only changed very slightly. Classic is assumed that the climax also has the highest production of biomass which is available on a site. The climax utilized its resources most effectively ( would be even more useful free resources, they might even be utilized by adventitious species. Thus the succession would go further, the endpoint was not reached ).

Klimaxgesellschaften / Klimaxstadien

The climax concept in botany goes back to Frederic Edward Clements. In its original version, he walked out of a uniform for each climate zone plant community that would eventually prevail at sufficiently long development time, everywhere and at all locations ( " Monoklimax "). In the modern environmental specialist discussion, the term is usually used with a modified perspective and meaning. In general, it is believed that very different locations would not completely leveled ( " Polyklimax "). In addition (eg cyclic ) changes are also accepted in the climax as a possibility. The climax vegetation corresponds to (largely) the changes introduced by the botanists Reinhold Tüxen concept of " potential natural vegetation ". ( Difference: Permanent Location changes in the course of succession are not considered). According to the prevailing view, the climax vegetation is except for extreme and exceptional locations a largely closed forest in Central Europe. On most sites it is a plant species-poor ( Book ) forest. Only on special locations to find other Klimaxgesellschaften. Moore usually form high moors as climax stage; High mountainous regions, cotton turn form other Klimaxstadien. Other exceptions are, inter alia azonal forest communities, such as riparian forests, swamp forests.

It should be noted, however, that some companies are subject to a natural dynamics (eg floodplains with regular floods ). Here is the climax vegetation is never reached under certain circumstances due to this ( natural ) disturbances. It will also discuss ongoing clearings in Klimaxwald due to ( natural) disturbance by large herbivores (see Megaherbivorenhypothese ).

See also: Potential natural vegetation.

Mosaic cycle theory

The mosaic cycle theory (also mosaic - cycle concept ) goes back to Kurt Michael Zukrigl and has been touted in recent decades, notably by Hermann Remmert. It is based, instead of a uniform Klimaxstadiums of a mosaic-like structure, exist in a wide variety of successional stages next to each other.