Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: alternative states

Sortuj według:

Ogranicz wyniki do:

Size-structured interactions and the dynamics of aquatic systems

Persson Lennart, Roos André M.

Polish Journal of Ecology

2006

Vol. 54, nr 4

621-632

Size variation within species as a result of individual growth and development over the life cycle is a ubiquitous feature of many aquatic organisms. We review the implications of this size variation for the dynamics of aquatic systems. Ontogenetic development results in differences in size dependent competitive abilities between differently sized individuals giving rise to cohort cycles that are qualitatively different from traditional predator prey cycles. Size-dependent interactions also mean that the type of interaction - competitive or predatory - changes over the life cycle as a result of an increase in size. At the intraspecific level, cannibalistic interactions may, depending on the life history characteristics of the cannibal, give rise to either equilibrium or cycles driven by a mixture of inter-cohort cannibalism and competition. In multispecies contexts, size variation and particularly food dependent growth lead to the presence of alternative states involving catastrophic collapses. These size-structured interactions have so far been mainly demonstrated for fish and cladocerans, but do have whole lake food web ramifications.

Subfossil remains of chironomidae from two shallow lakes representing extreme alternative states

Halkiewicz A.

Studia Quaternaria

2005

Vol. 22

45-49

The remains of Chironomidae in the recent sediments of macrophyte-dominated Lake Rotcze and phytoplanktondominated Lake Syczyńskie (Polesie Region) were analyzed in order to check their suitability for diagnosing the lake status according to the alternative equilibria concept and thus also the development of submerged vegetation. In both lakes chironomid capsules were predominated by phytophilous taxa but their relative abundance was higher in the phytoplankton-dominated lake. The percentage of pelophilous taxa in the lakes did not exceed 10%. The taxa richness of both phytophilous and pelophilous assemblages was higher in the macrophyte-dominated lake. Therefore I conclude that the presence of phytophilous forms, and even their prevailing contribution in the total chironomid numbers can not be sufficient to prove the existence of a macrophytic state of a lake. In order to put a proper diagnosis on the development of vegetation in the past, the detailed analyses of the qualitative and quantitative structure of both ecological assemblages is needed.