Keywords:
mainland dune
coastal dune heath
organic matter
nutrients
fire
Contact: Peter Vestergaard, Botanical Institute,
University of Copenhagen, Øster Farimags-gade 2 D, DK 1353
Copenhagen, Email: peterv@bot.ku.dk
Location: Denmark, North Sea Coast, Hansted reserve
The Hansted Reserve
The Hansted reserve in NW Jutland includes 3399 ha of sand dunes,
dry and moist dune heath, oligotrophic fens and dune lakes on
a former seabottom, which has been above sea level since the Stone
Age.
On August 11 and 12 in 1992, lightning caused a fire which burnt
an area of approximately 175 ha with an average size of approximately
400 m x 3.5 km. Mainly three types of heath were destroyed and
investigated: dry dune heath, dominated by Empetrum nigrum
and mosses; moist dune heath, dominated by Empetrum nigrum,
Vaccinium uliginosum and mosses; wet heath, dominated by
Erica tetralix and Molinia coerulea.
Observation
In December 1992 an investigation into the effects of the fire
on the vegetation and subsequent revegetation processes was initiated
by the Department of Plant Ecology, University of Copenhagen.
The study was mainly based on permanent plots in the burnt area
and reference plots in unburnt vegetation and focused partly on
the loss of organic matter and the minerals N, P and K, caused
by the fire, partly on the processes of vegetational succession
after the fire.
Results
The total amount of organic matter as well as the content of N,
P, and K decreased significantly in all heath types after burning
in the order: moist heath > dry heath > wet heath. The absolute
and relative losses of the three elements decreased in the order
N > K > P. The losses were caused during the fire by volatilization
and transport of ash by the smoke, as well as after the fire through
erosion, leaching or windblow. Based on the magnitude of the total
loss of organic matter and minerals from the burnt heath and on
estimated rates of atmospheric deposition it is estimated, that
for reestablishment of the former conditions a regeneration time
between 6 (replacement of K in wet heath) and 333 years (replacement
of P in moist heath) is needed, depending on the focused heath
type as well as on the content. In summer 1995 the burnt wet heath
already appeared almost as luxuriant as in the unburnt area, while
the moist and the dry heath were far behind.
Perspective
Nowadays, dune heaths are threatened by spread of the alien Pinus
mugo and management by fire could be an appropriate tool to
maintain dune heath vegetation. In this context the results of
this study point out the importance to carry out burning treatment
in heathland only under controlled conditions. It is especially
important to choose the optimum combination of wind, dry aboveground
biomass and moist ground, to retain sufficient amounts of nutrients
as well as living seeds and below-ground plant parts, to ensure
a fast recovery of the vegetation.
The study continues
Since 1992 the soil and species composition in the permanent plots
and within the burnt area in total has been recorded most years.
The development will be followed in the coming years in order
to achieve knowledge of the succession processes in a large, varied
dune and dune heath area after a fire.
Hansted reserve
References
- Vestergaard, P. & V. Alstrup (1996): Loss of organic
matter and nutrients from a coastal dune heath in northwest
Denmark caused by fire. Journal of Coastal Conservation 2: 33-40.
EUCC. Opulus Press Uppsala. Sweden. (KJc96a)
