Zeegerst (Hordeum marinum Huds.) op Noord-Nederlandse vastelandskwelders

In the Netherlands Hordeum marinum approaches the northwestern fringe of its area. It has strongly declined and is now considered an endangered species. Sofar its ecology and sociology had only been investigated in the SW of the country. There it mainly occurs on salty sites inside the dikes and is often accompanied by Parapholis strigosa and Puccinellia distans subsp. distans. In the N of Friesland and the NW of Groningen along the Wadden Sea the authors recorded Hordeum marinum in a range of localities in salt-marshes in the Puccinellia maritima belt in lower parts of the grassy marsh and in somewhat larger numbers in the Festuca rubra belt higher on. However, its main occurrence is on the summer embankments which are only reached by the flood at storm surges. Halophytes play a minor part in this belt; lower on, Agrostis stolonifera is prominent, higher on Lolium perenne. Locally Hordeum marinum itself may dominate over one or more square meters. Generally its habitat can be characterized as a short turf, mostly grazed by sheep (which avoid Hordeum because of its bristles), on a flat or somewhat sloping, even surface, with dicots usually keeping in the background. Outside the grazed area it may appear in disturbed sites. In its pattern of occurrence Hordeum marinum does not show a clear correlation with other annuals, though it is fairly often accompanied by Polygonum aviculare and Spergularia salina.