The effect of human trampling on a sand dune ecosystem dominated by Empetrum nigrum.
The influence of trampling was studied on the outer dune heath of Skallingen, southwest Jutland. The total number of passages and the period of time over which trampling occurred were varied independently, on areas that had either received fertilizer applications or were unfertilized. There was a linear relationship between the depth of the paths and the number of passages. 2560 passes lowered the soil surface by 28 mm. The width of paths increased with increasing numbers of passages. The paths were slightly deeper when trampled on a single day than when trampled over a period of 4 months. Relative cover of the vegetation was reduced with increasing numbers of passages; after 200 passages cover was 50%. This low carrying capacity is suggested to be the consequence of reduced vigour of the dominant species Empetrum nigrum, although it is not reflected in frequency measurements of this species. The frequency of four species E. nigrum, Festuca rubra, Ammophila arenaria and Veronica officinalis was largely unaffected by 150 passages but only two species, Empetrum nigrum and Hypnum cupressiforme, survived 2560 passages. Addition of fertilizer only slightly increased plant cover on the paths but tended to produce a vegetation dominated by grasses.