Keywords:
onshore barrier dunes
mowing
sod removal
vegetation
soil fauna
soil micromorphology
Location: The Netherlands, North Sea, province North
Holland
The Zwanenwater, province North Holland
The Zwanenwater reserve is a dune area, situated in the coastal
dunes of the northern part of the province North-Holland, covering
an area of 586 ha. In 1793, a sanddike was built, which connected
the mainland with two Wadden Islands, Oghe and Huisduinen. West
of this dike the area could develope as a polder. The area consists
mainly of two dunerows situated parallel to the coast with a big
humid valley between, in which two shallow lakes are located.
Since 1973 the Zwanenwater has been owned and managed by ‘Natuurmonumenten’,
the Dutch national society for nature conservation.
The study area is located south of Callantsoog, in a primary wet
dune valley. The groundwater level here is below the surface of
the sample plots, except for very rainy periods, but varies in
depth throughout the year. The dry area surrounding the dune slack
is occupied by heathland. Under the heath, soil of Gleyic Arenosol
is formed, the original sand is well-sorted and non-calcareous.
Monitoring
The vegetation in the dune slack has been mown since 1940, the
sod was removed from restricted areas in the slack at various
times in the past (1980, 1985, 1987 and 1991). The management
practices were set up to interrupt the succession and re-establish
early successional stages and natural, dynamic features, and to
give pioneer species a chance. To report the following ecological
changes, the vegetation, soil fauna and soil profile were monitored
over a period of 13 years. The monitoring began after the first
sod removing in 1980.
Results
The vegetation which has been mown since 1940, shows a pioneer
vegetation adapted to wet dune slack conditions. The same applies
to the soil micromorphology and the soil biota, the new species
that appear are particularly adapted to humid soil conditions.
Most of the characteristics of the soil micromorphology appear
to be restored after 8 years.
However, the three aspects are interdependent, this means, changes
of vegetation by management affect the soil micromorphology and
microclimate, both are responsible directly for water conditions
and indirectly for soil biota colonization.
The effect of the sod removal was more drastic. With respect to
vegetation, a number of pioneer species occur in sod-removal plots
only. Species diversity increased with time after sod-removal
as well as total cover and herb cover, but after 13 years the
diversity of sod-removal and control plots are the same, whereas
the cover has only reached 80 % of the control plots. Abundances
of microarthropods on sod removal plots are extremly low, the
re-colonization is in agreement with the age of the plots after
sod removal. There is generally an increase in soil development
with the age of sod removal, but even after 13 years the Ah horizon
is no more than a fraction of its original thickness.
During the 13 years of observation, neither the vegetation, nor
the soil fauna or soil profile have fully recovered. So the goal
to interrupt succession and re-establish pioneer species has been
reached.
Location of plots and profiles a to f in the Zwanewater dunes,
Callantsoog, the Netherlands
Legend:
a = original heath surface, b = mown heath surface;plot name
with sod removed in year: c: 1991, d: 1987, e: 1985 and f: 1980.
P = semi-pernamentpool; R = vegetation with Phragmites australis
and Carex spp.; DR = vegeation with Erica tetralix. PU = location
of the piezometer no. 2 of the Department of Environmental Research,
University of Utrecht
References
- Klomp, W.H. (1989): Het Zwanenwater: a dutch dune wetland
reserve. In: van der Meulen, Jungerius & Visser. Perspectives
in Coastal Dune Management. SPB Academic Publishing bv. The
Hague. The Netherlands. (BNd).
- Jungerius, P.D., H. Koehler, A.M. Kooijman, H.J. Muecher
& U. Graefe (1995): Response of vegetation and soil ecosystem
to mowing and sod removal in the coastal dunes ‘Zwanenwater’,
the Netherlands. Journal of Coastal Conservation 1: 3-16. (KJc95a).
- Vereniging Natuurmonumenten (1996): Complete Gids Natuur-
en Wandelgebieden in Nederland. Vereiniging Natuurmonumenten.
Graveland.
