Article (refereed) -postprint Eco-hydrological Requirements of Dune Slack Vegetation and the Implications of Climate 1

ion, afforestation, urbanisation (Grootjans et al. 1998; Martinez et al., 2004; Provoost 106 et al., 2011), nitrogen deposition (Jones et al., 2004; Plassmann et al., 2008; Sival and 107 Strijkstra-Kalk, 1999) and from grass and scrub encroachment or exotic species invasion 108 (Martinez et al., 2004). In addition, changes in evapotranspiration due to vegetation change or 109 management will affect the water balance (Davy et al. 2010; Ford et al. 2012). An emerging 110 threat is climate change, which may shift the biogeographical range of dune slack species, but 111 which also alters the dune environment. Changes in precipitation and temperature affect 112 groundwater levels directly by altering the delicate balance between rainfall and 113 evapotranspiration, which controls recharge. Sea-level rise or shoreline erosion act indirectly 114 on groundwater levels by altering water table gradients (Clarke and Sanitwong Na Ayutthaya, 115 2010; Saye and Pye, 2007). Modelling of groundwater trends for dune slacks in a sand dune 116 system in north west England based on long term records, predicted a substantial lowering of 117 water levels of 1 to 3 metres over the next 90 years (Clarke and Sanitwong Na Ayutthaya, 118 2010). Physiological adaptations typical of plants growing on humid calcareous substrates 119 can make them less resilient to rapid habitat changes (Bakker et al., 2007; Grootjans et al., 12