1. Department of Biology, Ecosystem Management Research Group; University of Antwerp; Universiteitsplein 1C B-2610 Wilrijk Belgium
2. Department of Biology, Plant and Vegetation Ecology Research Group; University of Antwerp; Universiteitsplein 1C B-2610 Wilrijk Belgium
3. VITO, Unit Environmental Modelling; Boeretang 200 B-2400 Mol Belgium