Keywords:

onshore barrier dunes, island barrier dunes, tourism, dune paths, thatching, vegetation, soil fauna

Contact:	Gerd Weidemann, University of Bremen, UFT, D-28334 Bremen; e-mail: gweidem@uni-bremen.de
	Niels Christiansen, klitplantør, Blåbjergvej 50, Houstrup, DK-6830 Nørre Nebel

Location:	North Sea Coast, Denmark, S-W-Jutland, Houstrup Strand
	Baltic coast, Denmark, Sjælland, Køge Bay
	North Sea Coast, Germany, Spiekeroog

 

Houstrup Strand
Houstrup Strand is a large beach and dune area at the south-western coast of Jutland, Denmark, 30 km north of Blåvands Huk and part of the almost continuous coastal dune strip along the Danish North Sea coast. Tourism is the main economic basis of the whole region. It concentrates on the coastal zone. While holyday houses mostly are remote from the beach parking places are situated just behind the dunes. As a result a web of trampling paths between dune and beach and in the dunes has developed. Vegetation and soil fauna in the centre of a path, at its margin, and in adjacent undisturbed vegetation of white, grey and brown dune, respectively, has been studied.

Køge Bay
Køge Bay Seaside Park is an artificial dune landscape 15 km south of Copenhagen consisting of two offshore barriers with beach and dunes. Vegetation of a moderately trampled path on an Ammophila dune has been studied.

Spiekeroog
The East Frisian island of Spiekeroog is one of the dune islands bordering the German Wadden Sea. Vegetation and soil fauna of moderately frequented paths through white, grey and brown dune, respectively, have been studied.

Effects of human trampling on vegetation
Various dune plants are adapted to withstand injury depending on their habit of growth, position of the growing point and its ability to regenerate. The results of the investigations show a decrease of the vegetation cover of the paths depending on trampling intensity and vegetation type.Moderate trampling may increase spatial heterogeneity and thus increase species number as a result of changed competition pressure: species suffering from competition in untrampled situation may profit from trampling which suppresses sensitive but competitive species. This may especially occur at the path margins. Therefore, low levels of trampling may be acceptable to maintain species diversity while heavy trampling decreases species diversity and plant cover and promotes wind erosion when bare soil is left.

Effects of human trampling on soil fauna
Soil fauna is also dramatically reduced in the centre of trampling paths. This may be caused by increased bulk density and the associated loss of pore space and by decreased plant cover, which would result in changed microclimate at soil surface and soil humidity. Collembola communities show reduced density and species number. Small euedaphic species are dominant. Densities of Collembola and predatory mites (Gamasina) ares raised above that of adjacent undisturbed vegetation at the path margins in yellow and brown dune. - The analysis of the collembolan fauna as to species and life form composition is recommended to monitor the soil state, e.g. during regeneration after compaction.

Management measures
To prevent soil erosion by wind, which may lead to large blowouts, dune paths with more or less destroyed vegetation are either covered with conifer branches to keep people away from further using them and leave time for regeneration. Strongly frequented path are thatched with hay, straw or wood chips.

Effects of path thatching on dune vegetation
The thatching material often contains seeds and it contains nutrients. As a consequence the path margins become heavily eutrophied, as can be seen from the darker green colour of the plants and by the masty growth of many species, typical dune species as well as allochthonous species.Furtheron, at Houstrup Strand 30 species of plants normally not found in coastal dunes were found along a main path over the white dunes between parking place and beech. But they did not spread into the adjacent dune area but remained restricted to the path margins presumably due to the better adaptation of dune plants to the habitat under normal competition. Where the influence of wind and salt spray is reduced due to the distance from the sea, thatching with hay and straw should be avoided to prevent the introduction of allochthonous plant species.

References

• Anthonsen, U.V. (1995): The influence of human trampling on the vegetation on artificial dune and coastal grassland in Denmark. In: Salman, A.H.P.M., H. Berends & M. Bonazountas (eds.): Coastal Management and Habitat Conservation: 427-438; EUCC, Leiden, The Netherlands (PCB96)
• Voigt, A. (1997): Anthropogene Veränderungen von Küstendünen: Untersuchung von Trampelpfaden unter besonderer Berücksichtigung der Springschwänze (Collembola, Insecta). - Diploma Thesis, University of Bremen, FB 2., 59 pp.
• Koehler, H., H. Harder, J. Meyerdirks & A. Voigt (1996): The effect of trampling on the microarthropod fauna of dune sediments. A case study from Jutland. In: Jones, P.S., M.G. Healy & A.T. Williams (eds.): Studies in European Coastal Management: 221-231. Samara Publishing Ltd., Cardigan
• Voigt, A. & G. Weidemann (1998): Tourist Paths - Impact on vegetation and soil fauna. - In: Ovesen, C.H. (ed.): Coastal Dunes - Management, Protection and Research: 91-95;National Forest and Nature Agency & Geological Survey of Denmark and Greenland, Copenhagen.