Last reviewed: May 2026
The succession sequence on Baltic dunes
Vegetation succession on Baltic coastal dunes follows a broadly predictable sequence, though the pace and precise composition of each stage vary with local conditions — wave exposure, fetch, groundwater depth, and the history of disturbance at any given location. The sequence moves from a bare sand beach through embryonic dune, mobile foredune, semi-fixed dune, fixed grey dune, and eventually to dune heath or dune woodland, depending on conditions.
Each stage in this sequence alters the environment in ways that make it less hospitable to pioneer species and more hospitable to the next stage's community. Pioneer annuals modify sand surface temperature and add minimal organic matter. Grasses produce root systems and litter that begin genuine soil formation. Heath and woodland communities eventually create shaded, humus-rich conditions where the original pioneers could no longer survive.
Upper beach and embryonic dune flora
The upper beach above the storm tide line carries a sparse assemblage of highly stress-tolerant annual and perennial species. On the Polish Baltic coast, this zone typically includes sea rocket (Cakile maritima), prickly saltwort (Salsola kali), and sea sandwort (Honckenya peploides). These plants establish from seed deposited with wrack material or windblown from adjacent dune communities.
Their contribution to dune formation is indirect but meaningful. By creating surface roughness, even scattered plants reduce wind speed at the sand surface, causing localised sand deposition that raises small mounds — the embryonic dune stage. These mounds provide the slightly elevated and sheltered conditions in which Ammophila arenaria can establish from seed or vegetative fragments.
Habitat type 2110
Embryonic shifting dunes are classified as Annex I habitat 2110 under the EU Habitats Directive. On the Polish coast, these habitats are typically narrow and discontinuous, subject to frequent disturbance from storm overwash. Their presence is a prerequisite for the foredune formation process to begin.
Fixed dune communities: grey dune flora
Once sand mobility declines behind an established foredune crest, a quite different plant community develops. Fixed grey dunes — named for the cryptogam crust of lichens and mosses that covers much of the bare ground — support a diverse assemblage of mostly perennial species adapted to well-drained, nutrient-poor, and often acidic conditions.
On the Polish coast, the fixed grey dune community characteristically includes sand fescue (Festuca arenaria, also F. polesica in eastern sections), sand sedge (Carex arenaria), stonecrop (Sedum acre), wild thyme (Thymus serpyllum), and several species of lichen from the Cladonia genus. The lichen-dominated surface between vascular plant tussocks is particularly important for reducing erosion by rain impact and, when dry, by wind.
Grey dune habitats (Annex I type 2130) are considered one of the most species-rich dune vegetation types in northern Europe. Their richness reflects the combination of low nutrient availability, variable moisture, and long-term stability that allows many slow-growing specialists to persist without competitive exclusion by fast-growing grasses.
Carex arenaria and its network role
Sand sedge (Carex arenaria) deserves particular mention as a structural component of transitional and fixed dune communities on the Polish Baltic coast. Unlike most sedges, Carex arenaria spreads by a monopodial rhizome that grows in a straight line through sand, producing aerial shoots at regular intervals. This architecture makes it effective at rapidly colonising bare sand patches within otherwise vegetated dune terrain.
Where Ammophila arenaria begins to senesce on stable surfaces, Carex arenaria often moves into the gap, maintaining surface cohesion at a stage when the primary pioneer is declining. The two species can coexist at intermediate sand mobility levels, with Ammophila dominant where sand input is regular and Carex dominant on more stable surfaces.
Rhizome network
Carex arenaria rhizomes can be traced across fixed dune surfaces for many metres, forming a network that binds the upper sand profile even where aerial shoot density appears sparse. In studies of dune surface cohesion in northwestern Europe, the combined rhizome mass of Carex arenaria and Festuca species has been found to contribute substantially to erosion resistance on semi-fixed dune surfaces.
Dune heath communities
At the inland extent of the dune succession, where soil development is most advanced, heath communities dominated by heather (Calluna vulgaris) and crowberry (Empetrum nigrum) replace the open fixed-dune grassland. On the Polish Baltic coast, this transition is visible in the inland sections of Słowiński National Park and on older dune ridges along the Pomeranian coast.
Dune heath (Annex I habitat 2140 — decalcified fixed dunes with Empetrum nigrum) represents the climax of the succession in areas where groundwater remains below root depth and the substrate remains predominantly sandy. Where groundwater is closer to the surface, the succession can diverge toward dune slack communities with characteristic wetland species.
Dune slack vegetation
Between parallel dune ridges, deflation hollows and inter-dune depressions known as slacks develop wherever the land surface drops close to or below the water table. Dune slacks support a distinct and often highly specialised vegetation type. On the Polish coast, slacks within dune systems support creeping willow (Salix repens), marsh orchids (Dactylorhiza spp.), grass of Parnassus (Parnassia palustris), and various rush and sedge species.
Slack vegetation contributes to dune stability not through direct sand binding at the surface but through the moisture retention and organic matter accumulation it drives. A well-vegetated slack raises overall dune system resistance to deflation by maintaining elevated groundwater levels that prevent desiccation of the sand surface in surrounding areas.
Non-native species and management
The native dune flora of the Polish Baltic coast faces pressure from several introduced species. Sea buckthorn (Hippophae rhamnoides), though native to some coastal areas further east, has been extensively planted for erosion control on the Polish coast and has spread beyond planted areas, forming dense thickets that displace open dune communities. Its nitrogen-fixing root nodules alter soil chemistry in ways that favour competitive grasses over the nutrient-limited specialists of grey dune habitat.
Japanese rose (Rosa rugosa) is another widely naturalised species on Polish coastal dunes, introduced for ornamental purposes and erosion control. It forms dense, thorny thickets on fixed dune surfaces, outcompeting native shrubs and suppressing the low-growing species typical of grey dune communities. Management efforts within Słowiński National Park and other protected areas have focused on mechanical removal of established sea buckthorn and Rosa rugosa from areas where grey dune habitat conservation is a priority.
