Environmental Engineering Reference
In-Depth Information
metallophytes into the adjacent agricultural fields (Ernst
1974
). In the Harz
area, large dams have been constructed to avoid regular riverbank flooding
to the detriment of maintaining the alluvial heavy-metal vegetation (Ernst et al.
2004
). The alluvial tertiary sites of the Geul valley can be species-rich, but
originate from metal-ore dressing facilities.
Classification of European metallophyte vegetation
The heavy-metal content of soil is one of the most important edaphic factors
determining vegetation composition. Heavy-metal toxicity of the soil, as well as
low nutrient status, poorly developed soil structure and often water-restricted
conditions maintain open vegetation, retarding succession. Many sites also
harbour important populations of rare bryophytes, lichens and insects in
addition to metallophytes. Being immobile, plants can survive only by adapting
their physiological processes, and because metal tolerance is so specific, eco-
types of plants are restricted to individual sites, so-called 'local endemism'.
Heavy-metal plant communities of Europe are grouped within the vegetation
order of Violetalia calaminariae. Ernst (
1974
,
1976
) allocated alpine heavy-metal
vegetation to the vegetation alliance Galio anisophylli-Minuartion vernae with
Galium anisophyllum, Poa alpina, Euphrasia salisburgensis and Dianthus sylvestris and
in the Italian and Austrian Alps the hyperaccumulator Thlaspi rotundifolium
subsp. cepaeifolium and with the endemic Viola dubyana. In Western-central
and Western Europe heavy-metal vegetation belongs to the alliance Thlaspion
calaminariae with Arabidopsis (Cardaminopsis) halleri in addition to T. caerulescens
(see also Brown
2001
), and in Central Europe to the alliance Armerion halleri
(see also Dierschke & Becker
2008
). The heavy-metal vegetation types in the
Eastern Alps of Austria, Italy and Slovenia are included within the Thlaspion
rotundifolii (Punz & Mucina
1997
), although in Slovenia T. rotundifolium is substi-
tuted by T. praecox (Vogel-Miku
ˇ
et al.
2007
). In Scandinavia, Lychnis alpina is a
marker species for metallophyte vegetation (Ernst
1974
,
1990
; Brooks & Crooks
1979
; Nordal et al.
1999
). The Violetum calaminariae can be subdivided geograph-
ically in eastern and western areas with the blue flowering zinc violet (Viola
guestphalica) in the Violetum calaminariae westfalicum at Blankenrode (Germany)
its only site in the world, and the yellow flowering Viola lutea subsp. calaminaria
in the Violetum calaminariae rhenanicum. In the British Isles, Rodwell et al. (
2007
)
allocate the metallophyte vegetation as Festuca-Minuartia community to the
calaminarian grassland of the Violetalia calaminariae.
Classification of metallophytes
The following classification of metallophytes is adapted from Lambinon and
Auquier (
1963
):
