The effect of habitat fragmentation and abiotic factors on fen plant occurrence
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The effect of habitat fragmentation and abiotic factors on fen plant occurrence Hester Soomers • Derek Karssenberg • Jos T. A. Verhoeven Pita A. Verweij • Martin J. Wassen
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Received: 4 May 2012 / Accepted: 22 November 2012 / Published online: 9 December 2012 Ó Springer Science+Business Media Dordrecht 2012
Abstract Human landscape modification has led to habitat fragmentation for many species. Habitat fragmentation, leading to isolation, decrease in patch size and increased edge effect, is observed in fen ecosystems that comprise many endangered plant species. However, until now it has remained unclear whether habitat fragmentation per se has a significant additional negative effect on plant species persistence, besides habitat loss and degradation. We investigated the relative effect of isolation, habitat size, and habitat edge compared to the effect of habitat degradation by including both ‘fragmentation variables’ and abiotic variables in best subsets logistic regression analyses for six fen-plant species. For all but one species, besides abiotic variables one or more variables related to fragmentation were included in the regression model. For Carex lasiocarpa, isolation was the most important factor limiting species distribution, while for Juncus subnodulosus and Menyanthes trifoliata, isolation was the second most important factor. The effect of habitat size differed among species and an increasing edge had a negative effect on the occurrence of Carex lasiocarpa and Pedicularis palustris. Our results clearly show that even if abiotic H. Soomers M. J. Wassen (&) Environmental Sciences, Copernicus Institute of Sustainable Development, Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, The Netherlands e-mail: [email protected] Present Address: H. Soomers Vereniging Natuurmonumenten, Regio Zuid-Holland en Zeeland, Stationsplein 45, 3013 AK Rotterdam, The Netherlands D. Karssenberg Department of Physical Geography, Faculty of Geosciences, Utrecht University, PO Box 80115, 3508 TC Utrecht, The Netherlands J. T. A. Verhoeven Ecology and Biodiversity, Faculty of Science, Utrecht University, PO Box 80058, 3508 TB Utrecht, The Netherlands P. A. Verweij Energy and Resources, Faculty of Geosciences, Copernicus Institute of Sustainable Development, Utrecht University, PO Box 80058, 3508 TB Utrecht, The Netherlands
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Biodivers Conserv (2013) 22:405–424
conditions are suitable for certain species, isolation of habitat patches and an increased habitat edge caused by habitat fragmentation affect negatively the viability of characteristic fen plant species. Therefore, it is important not only to improve habitat quality but also to consider spatial characteristics of the habitat of target species when deciding on plant conservation strategies in intensively used landscapes, such as fen areas in Western Europe and North America. Keywords Dispersal limitation Habitat area Habitat degradation Habitat edge Isolation Logistic regression
Introduction Over the last decades, human impa
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