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Extremstandorte und Strategienvielfalt - ein Beispiel aus amazonischen Überschwemmungswäldern

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons56855

Parolin,  Pia
Working Group Tropical Ecology, Max Planck Institute for Limnology, Max Planck Institute for Evolutionary Biology, Max Planck Society;

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Citation

Parolin, P. (2002). Extremstandorte und Strategienvielfalt - ein Beispiel aus amazonischen Überschwemmungswäldern. Phyllodrom Journal, Tagungsband 2002, 34-48.


Cite as: http://hdl.handle.net/11858/00-001M-0000-000F-DE09-7
Abstract
How diverse are extreme sites? How diverse can the species be, and their adaptations and life strategies? How specialized do the species have to be, which ecological amplitude can / must species on extreme sites possess? The term extreme site is used without a clear definition in literature. This paper gives a definition and aims at answering the questions mentioned above with the help of examples, which are focussed on the ecology of trees. A definition of the term ,extreme site' can be found in relation to Larcher' s biological concept of stress: extreme sites are thus sites where one or more factors of the local setting of environmental factors are under- or overrepresented to an extent that the organisms inhabiting it can live there only with the formation of special adaptations. Such sites generally may be found in polar or alpine deserts, dry deserts or inselbergs which normally are not colonized by trees. Ecosystems with extreme factors where trees dominate, e.g. gallery forests in arid zones or mangroves along tropical coasts, normally show a low diversity of species and growth strategies. Amazonian floodplains also show all characteristics of extreme sites. A very long uninterruted period of flooding with a high amplitude, rapid changes of water level, anoxic conditions in the rhizosphere, high sedimentation in Várzea, lack of nutrients in sediment-poor Igapó, high mechanical stress and even drought lead to difficult conditions for growth of all organisms living in this ecosystem. Nevertheless, Amazonian floodplain forests have a very high diversity of species and life strategies, also within the phanerophytes. This diversity may result from the fact that this extreme site has only a reduced number of factors representing stress for the trees, and the regular disturbances may even represent a driving force for resistance and adaptive evolution. The high complexity of the system and the short but regular occurrence of factors enhancing tree growth allow the formation of highly diverse survival strategies. The species are seldom highly specialized - most have high ecological amplitudes. In these floodplains, specialization is low enough to allow the trees to react to changing environmental conditions, and is high enough to allow a high diversity along the hydric and edaphic gradient.