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PARENT SESSION
Tuesday, August 8, 1:30-5:00 pm
COS 39 - Community ecology II: community dynamics and change
L-3, Lobby Level, Cook Convention Center
Presiders: K Beard and Y Wang

Habitat modification at different scales.

van Wesenbeeck, Bregje*,1, van de Koppel, Johan1, Bertness, Mark2, van der Wal, Daphne1, Herman, Peter1, Bakker, Jan3, Bouma, Tjeerd1, 1 Netherlands Institute of Ecology, Yerseke, The Netherlands2 Brown University, Providence, Providence, RI, US3 Rijks Universiteit Groningen, Groningen, The Netherlands

ABSTRACT- Feedbacks between organisms and the environment are a very general principle in ecology. Nevertheless the impact of feedbacks between organisms and the environment on community structure and ecosystem development is not always clear. Especially, because on different scales different feedback mechanisms are at work. Here we examine the impact of feedbacks between species and the environment from local scales to landscape scales on transitions between salt marshes and tidal flats. Our main aim was to investigate the importance of interactions between organisms and a-biotic variables in delaying ecosystem development. We found that scale-dependent feedback restricted tussock expansion at the edge of establishing Spartina tussocks. Secondly, transplantation experiments showed that sediment reworking by lugworms inhibited invasion of small Spartina seedlings on the mudflat. Finally, experiments showed a biomass threshold for Spartina settlement, which suggests that alternative stable states are present at the salt-marsh/tidal flat interface. Surprisingly, image analysis showed that salt marsh pioneer zones are not stable when considered on longer timescales. Still, these systems have potential for catastrophic shifts which should be taken into consideration for adequate restoration and management of salt marshes and patchy systems in general.

Key words: positive feedback, community ecology, intertidal habitat

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