Restoration possibilities of dry grasslands afforested by pine: the role of seed bank and remnant vegetation

Szabó, Anna and Ruprecht, Eszter (2018) Restoration possibilities of dry grasslands afforested by pine: the role of seed bank and remnant vegetation. Tuexenia, 38. pp. 405-418. ISSN 0722-494X (In Press)

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Abstract

Stipa-dominated steppe-like dry grasslands represent a great nature conservation priority in Romania and in the whole European Union. In Romania, due to their low productivity, many sites had been afforested by pines or black locust trees at the end of the 1950’s in order to raise economic value and to hinder landslides on the steep slopes. Economic expectations did not live up, thus afforested sites will increasingly be targeted for grassland restoration, especially in protected areas of the Natura 2000 network. We analysed seed bank and aboveground vegetation in a 40-year-old black pine plantation site established on a former dry grassland near Viișoara (Transylvanian Lowland), and compared to that of an adjacent intact dry grassland stand. In both stands, eight 5 m × 5 m plots for soil and vegetation analysis were established. Inside each plot, six cylinder-shaped soil cores of 4 cm diameter and 10 cm depths were drilled; soil samples from the same plot were subsequently mixed up. Soil sampling was carried out in early spring, 2008. We analysed seed densities and composition in soil samples using the seedling emergence method. In addition, we recorded percentage cover of plant species in the plots in June. We wanted to find out on what extent we can rely on the soil seed bank and remnant vegetation, if active interventions are planned to restore a grassland stand in the place of a pine plantation. In total, 293 seedlings belonging to 51 species have emerged from soil samples. Seed density in the soil seed bank of the pine plantation was substantially higher (3500 ± 2059 seeds m-2, 0–10 cm) than that of the intact grassland (1360 ± 469 seeds m-2, 0–10 cm). Our results showed that the seed bank of the plantation site, although not specifically species rich, may still contain a considerable amount of target species. In addition, we found strong populations of grassland species in the understory of the plantation as remnants of the former vegetation, which, together with seeds in the seed bank can ensure a good starting point to a successful natural regeneration after tree removal. Due to the presence of ruderal species in the seed bank and shrubs in the aboveground vegetation, light restoration measures comprising weed- and shrub control are necessary following the complete removal of trees. We propose the re-introduction of grazing in order to ensure the spontaneous regeneration by propagule transport to restoration sites.

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