Environmental Engineering Reference
In-Depth Information
In Belgium, the total coverage of the association Violetum calaminariae
encompasses only 38 ha, almost exclusively of the secondary type (Graitson
et al.
2003
). The quality of the majority of these sites has deteriorated in the last
in many sites being overgrown by shrubs and trees. The impact of fertilizers
and atmospheric deposition of nitrogen on nutrient-poor grasslands has accel-
erated this process.
Immediate action in pragmatic site management is imperative to protect
remaining metallophyte vegetation in Europe; this must be given priority in
nature conservation. It is clearly possible to regenerate secondary and tertiary
sites as Raskin (
2003
) and Van der Ent (
2008
) have shown. Urgent action
towards protecting metallophytes is also necessary because of the ever-increasing
threat of extinction and the rapid decline in the number of sites. Today almost
nothing is left of the former distribution compared to 50 years ago.
Site management
Depending on metal concentrations in the soil, metallophytes can thrive on
primary sites for thousands of years, on secondary sites for perhaps hundreds
of years, and on tertiary sites for less after the cessation of mining activities.
Metallophytes on secondary and tertiary sites are relics of local historic land
use and dependent upon site dynamics. To sustain the metallophyte commu-
nities, ecological management is necessary. Without management, these plant
communities face extinction due to vegetation succession and substrate
attenuation.
Most sites are small-scale, but are habitats for highly endangered plants
and can therefore be classified as especially valuable for nature conservation
(Pardey
2002
). Conservation management of metallophytes is strongly linked to
maintaining sites with high metal concentrations in the soil. To conserve and
develop secondary sites, disturbance and mixing of topsoil/subsoil is necessary
to sustain concentrations of metals high enough to hinder the succession of
grasses and herbs. Because metallophytes are generally of very low productivity
and, hence, uncompetitive, eutrophication remains a serious threat. Site man-
agement includes mowing and removal of hay, and/or removal of the top layer
of soil to reduce nutrient loadings (especially P) in the system and retard
vegetation succession.
Environmental legal protection within Europe
In contrast to former times, metallophytes are protected by legislation Europe-
wide. This protection strengthens conservation and can contribute to the
restoration of metallophyte vegetation. Under the EU Habitats Directive
Annex I (Fauna-Flora-Habitat), heavy-metal vegetation is coded as 'Calaminarian
grasslands of the order Violetalia calaminariae' under Code 6130. This also
