Multiple effects of land-use changes impede the colonization of open water in fen ponds

Authors

  • Judith M. Sarneel,

    1. Ecology and Biodiversity Group, Department of Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands; Department of Aquatic Ecology, Netherlands Institute of Ecology, P.O. Box 50, 6700AB, Wageningen, The Netherlands
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  • Merel B. Soons,

    1. Ecology and Biodiversity Group, Department of Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands
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  • Jeroen J.M. Geurts,

    1. Aquatic Ecology and Environmental biology, Institute for Water and Wetland Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands; B-WARE Research Centre, Radboud University Nijmegen, Toernooiveld 1 6525 ED Nijmegen, the Netherlands
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  • Boudewijn Beltman,

    1. Ecology and Biodiversity Group, Department of Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands
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  • Jos T.A. Verhoeven

    1. Ecology and Biodiversity Group, Department of Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands
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  • Co-ordinating Editor: Martin Hermy

  • Sarneel, J. M. (corresponding author, j.sarneel@nioo.knaw.nl): Ecology and Biodiversity Group, Department of Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands; Department of Aquatic Ecology, Netherlands Institute of Ecology, P.O. Box 50, 6700AB, Wageningen, The Netherlands
    Soons, M. B. (m.b.soons@uu.nl); Beltman, B. (b.beltman@uu.nl) & Verhoeven, J. T. A. (j.t.a.verhoeven@uu.nl): Ecology and Biodiversity Group, Department of Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands
    Geurts, J. J. M. (j.geurts@science.ru.nl): Aquatic Ecology and Environmental biology, Institute for Water and Wetland Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands; B-WARE Research Centre, Radboud University Nijmegen, Toernooiveld 1 6525 ED Nijmegen, the Netherlands

Abstract

Question: Dutch fen areas have become embedded in intensively used landscapes, resulting in biodiversity loss. Hence, plant species that colonize open water inducing the formation of species-rich floating peat mats have disappeared. Despite many restoration efforts, they have not returned. Is natural succession towards floating mats impeded by site conditions, dispersal limitations or changed biotic interactions?

Location: Six Dutch fen reserves: De Deelen, De Weerribben, De Wieden, Westbroek, Molenpolder and Terra Nova.

Methods: In 62 fen ponds we determined plant species richness and expansion into open water. We related these to habitat quality (chemical composition of soil and surface water, pond morphology), dispersal potential (distance to remnant populations, likelihood of dispersal) and biotic interactions (presence of muskrats [Ondatra zibethicus L.] and the keystone species Stratiotes aloides).

Results: Factor analysis showed that plants expanded further into open water and bank vegetation had higher species richness in areas with older ponds and lower muskrat densities. Locally, high turbidity hampered colonization. Whenever the water was clear, colonization was higher in shallow ponds, and in deep ponds only if Stratiotes was present. Species richness was negatively correlated to nutrient availability in soil and positively correlated to hydrological isolation (decreased sulphate concentrations). We also found that species richness was higher in sheltered banks.

Conclusions: Multiple habitat characteristics (turbidity, water depth, nutrient and sulphate concentrations) and the influence of muskrats and Stratiotes all play a role in the lack of restoration success in Dutch fen ponds. Dispersal limitations seem to be overruled by habitat limitations, as colonization often fails even when sufficient propagule sources are present, or when connectivity is high.

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