Question: Can lichen diversity of an earlier succession stage be restored in dune grassland after fire in a region with high nitrogen deposition?
Location: Calcium-poor coastal dunes in the Wadden district, The Netherlands.
Methods: We sampled dune grassland by using a large continuous transect of 4 m × 4 m blocks on both a south slope and a west slope. The sampling was conducted in the lichen-rich Violo-Corynephoretum in 1966, in the vegetation dominated by tall graminoids in 1990 and in the recovering vegetation for eight years after a wildfire in 1993. Vegetation succession in the blocks is visualised in stacked bar graphs and ordination diagrams (DCA). In 1966 relevés were made within the blocks, and from 1990 until 2001 permanent quadrats were studied.
Results: Between 1966 and 1990 the lichen-rich open grassland became dominated by tall graminoids and developed partly into a dwarf-shrub heath, resulting in a severe loss of lichen diversity. After the fire a lush vegetation of tall graminoids with an abundant moss cover developed. In 2001 the vegetation was still very different from the lichen-rich vegetation in 1966.
Conclusions: Fire alone will not change dunes dominated by tall graminoids into open lichen-rich grasslands in an area with high aerial nitrogen deposition. After fire, additional intervention is recommended, such as large-scale clearing of the burned vegetation and actively promoting deposition of sand, either blown in from foredunes, from re-activated blow-outs or artificially brought to the site.
Abbreviations: L = Light; N = Nitrogen; NMDS = Non-metric multidimensional scaling; PQ = Permanent quadrat; R = Acidity reaction; RD = Rijks-Driehoeksmeting; VC = Violo-Corynephoretum.