AND BÉLA TÓTHMÉRÉSZ

Alkali grasslands are included in the Natura 2000 Habitats Directive as Pannonic salt steppes and salt marshes (1530) priority habitats. They harbour a unique flora and fauna; thus, conservation and restoration of their biodiversity is of a high priority. Technical restoration is often necessary to mitigate the negative landscape-scale effects of agricultural crop production and to increase the area occupied by grasslands. Recovery of grassland vegetation can be facilitated by sowing seeds of target species. Low-diversity seed mixtures provide a cost-effective measure, as they are easily formulated and applied in large-scale grassland restorations. Between 2004 and 2008 a total of 760 ha of former croplands were sown with low diversity seed mixtures of appropriate species to restore basic alkali grasslands in Hortobágy National Park, East-Hungary. The seed mixture contained seeds of Festuca pseudovina and Poa angustifolia. After soil preparation seed mixtures were sown at a rate of 25 kg/ha in October. The sown fields were mown once a year. To follow vegetation changes, two 25 m2 sampling sites per field were established after sowing. To assess the effect of mowing on the vegetation, one sample site in each field was not mown after the third year. Biomass was sampled in the permanent plots to monitor vegetation changes. The rapidly Recovery of Alkaline Grasslands using Native Seed Mixtures 183 developing perennial cover effectively suppressed short-lived weeds in the aboveground vegetation, but allowed the preservation of their soil seed banks. We found that the high levels of biomass production typical of alkali grassland restorations in former croplands are beneficial for the suppression of short-lived weedy forbs, but might hamper the immigration of characteristic alkali grassland species. We stress that a long-term post-restoration management program is essential for sustaining recovered grassland biodiversity. This could be accomplished by mowing in the first few years, and later by extensive grazing by cattle and sheep. The latter management practice also supports the establishment of characteristic alkali grassland species