Investigations on long-term persistence of <i>Corynephorus canescens</i> populations in a large restoration area in an alluvial landscape (NW Germany)

Abstract

Open sand vegetation on inland dunes is among the most endangered vegetation types of Central Europe. Weakly competitive pioneer species with subatlantic distribution, such as the grey-hair grass (Corynephorus canescens), are the first colonizers. In two restoration areas in the border zone of meanders of the Hase river (Ems land, NW Germany), in part formerly under intensive agricultural management, Corynephorus pioneer vegetation (Spergulo vernalis-Corynephoretum canescentis) has been established by restoration measures. Newly created dune areas (''neodunes'') with low soil-nutrient conditions were created, inoculated and extensively grazed mainly by cattle (seldom horses). Inoculation was implemented by the transfer of mown and raked plant material from a target area (nature reserve area nearby). Ten years after the restoration measures C. canescens is still growing on all inoculated sites of the new dune systems and on old dune fragments, but the plant communities differ. A new settlement of C. canescens was observed on one open sandy site near the river. Differences in coverage of open sand, humus content of substrate as well as number and composition of competing plant species influence the vitality of Corynephorus individuals and the size of their populations. The tufts vary in frequency, size, vitality and number of dispersal units. With regard to these parameters the inoculated newly created dune areas differ significantly from the old dune fragment and the site with new spontaneous settling. The size of the tufts is correlated with the number of inflorescences and dispersal units. Tuft size corresponds to current growing conditions. Long-term persistence depends on a complex interacting network of several factors. High individual phytomass guarantees successful dispersal by influencing the numbers of inflorescences and diaspores. Long-term persistence of C. canescens populations in the complex of the new dune systems cannot be ensured under the current conditions (e. g. competition with other plant species, relatively high humus accumulation, lack of stronger dynamics). A higher grazing impact should enhance re-dynamization.