The effectiveness of ditch banks as dispersal corridor for plants in agricultural landscapes depends on species’ dispersal traits William F.A. van Dijk a,⇑ , Jasper van Ruijven a , Frank Berendse a , Geert R. de Snoo a,b a Nature Conservation and Plant Ecology Group, Department of Environmental Sciences, Wageningen University, PO Box 47, 6700AA Wageningen, The Netherlands b Institute of Environmental Sciences, Leiden University, PO Box 9518, 2300 RA, Leiden, The Netherlands article info Article history: Received 30 August 2013 Received in revised form 18 December 2013 Accepted 6 January 2014 Keywords: Agroecology Agri-environment scheme Agrobiodiversity Grassland Riparian buffer strip abstract The effectiveness of agri-environment schemes (AES) in enhancing biodiversity in agricultural landscapes is still strongly debated. In the Netherlands, one of the most widely implemented AES is the management of ditch banks to enhance plant species diversity. Previous research has shown that this type of AES has not led to increases in plant diversity. However, this work also showed that the success of this type of AES may depend on the presence of source populations in the surrounding areas. In this study we investigated if species-rich nature reserves can act as seed sources for agricultural ditch banks under AES and whether this function of nature reserves differs among plant species with different dispersal capacities. We used data collected by farmers over a 10 year period to analyse trends in species richness of target plants and in different dispersal groups in ditch banks under AES at different distances from nature reserves. Our results demonstrate that nature reserves can act as species rich sources in agricultural landscapes and that adjacent AES ditch banks can facilitate the colonisation of the surrounding agricultural land- scape. However, the suitability of ditch banks as corridors depends on the dispersal capacity of a species. Particularly water-dispersed species clearly spread from nature reserves into the surrounding agricul- tural landscape along ditches. In contrast, species without adaptations to disperse over long distances do not show these spatiotemporal patterns. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction For decades, biodiversity has been declining in agricultural areas worldwide due to intensification of agriculture and the aban- donment of species-rich areas under extensive agricultural man- agement (Foley et al., 2005; Stoate et al., 2009; Strijker, 2005). This trend is not expected to halt in the upcoming decades (Tilman et al., 2001), despite international agreements like the Convention on Biological Diversity (CBD), which attempts to enhance global sustainable development in farming systems (Balmford et al., 2005). In Europe, the decline in biodiversity on farmland has been particularly strong in countries in the lowlands of north-western Europe, such as The Netherlands (Donald et al., 2001; EEA, 2009; Geiger et al., 2010; Stoate et al., 2009). Measures implemented in Europe to halt the decline in biodiversity on farmland include the creation of nature reserves in which extensive agriculture takes place to conserve biodiversity, and agri-environment schemes (AES), which are designed to restore biodiversity on farmland. These schemes serve two important functions in the protection of biodiversity. First, they increase the area of land under manage- ment to conserve biodiversity. Second, land under AES may act as corridors or stepping stones in the landscape to connect frag- mented nature reserves (de Snoo et al., 2012; Donald and Evans, 2006; Geertsema et al., 2002; van Dorp et al., 1997). However, AES in Europe vary widely in their effectiveness in actually increas- ing biodiversity (Berendse et al., 2004; Feehan et al., 2005; Kleijn et al., 2006, 2011; Kuiper et al., 2013; Peach et al., 2001; Wilson et al., 2007). In the Netherlands, a substantial part of AES is focused on plant-species richness in ditch banks. Over the last decades, most plant species of former species-rich meadows have been dri- ven back to field margins and extensively managed nature reserves (Geertsema et al., 2002; Kleijn et al., 2001). AES focused on these plant species include the management of the outermost metre of ditch bank of pastures, where no fertiliser or ditch sludge may be deposited (DLG, 2000). The most important indicator to monitor the effect of this AES is the richness of plant species of ditch banks. Previous research in the Netherlands has shown that although AES ditch banks on average contained more species than non- AES ditch banks, no further increase in the number of species in AES ditch banks was found after longer periods of AES (Blomqvist et al., 2009; Kleijn et al., 2001, 2004; van Dijk et al., 2013a). Expla- nations for these disappointing results include soil nutrient status that did not reach sufficiently low levels, high productivity and 0006-3207/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biocon.2014.01.006 ⇑ Corresponding author. Tel.: +31 317 484471; fax: +31 317 419000. E-mail addresses: william.vandijk@wur.nl (W.F.A. van Dijk), jasper.vanruijven@ wur.nl (J. van Ruijven), frank.berendse@wur.nl (F. Berendse), snoo@cml.leidenuniv. nl (G.R. de Snoo). Biological Conservation 171 (2014) 91–98 Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon