Environmental Engineering Reference
In-Depth Information
3.
V
EGETATION OF
A
LKALI
M
ARSHES
Alkali marshes are generally species-poor habitats characterised by the dominance of tall-
growing salt-tolerant monocot species (like
Bolboschoenus
spp.,
Schoenoplectus
tabernaemontani
or
S. littoralis
). In stands formed on moderately alkali soils
Phragmites
australis
is generally dominant. In most cases a second vegetation layer is typical, consisting
of
Agrostis stolonifera
,
Eleocharis uniglumis
and
Puccinellia limosa
. Alkali marshes harbour
several salt-tolerant plant species like
Acorellus pannonicus, Aster tripolium
spp
.
pannonicum, Atriplex litoralis, Cirsium brachycephalum
and
Chenopodium chenopodioides
(Eliáš et al. 2012). In spring, when permanent water cover is typical several aquatic plant
taxa, such as
Batrachyum
spp.,
Hydrocharis morsus-ranae
,
Lemna
spp.,
Salvinia natans
and
Utricularia
spp. are present in alkali marshes. Generalist wetland species (like
Alisma
spp.
,
Carex
spp.
, Eleocharis palustris, Epilobium tetragonum, Iris pseudacorus, Lycopus
spp
.,
Lythrum virgatum
and
Mentha aquatica
) which can tolerate moderate salt concentrations are
also typical (Borhidi et al. 2012). Decrease in salt content supports these generalist species
and the dominance of
Phragmites australis
, leading to the transformation of alkali marshes
into non-alkali wetlands. Alkali marshes show a highly mosaic pattern, due to the uneven
pattern of the salt accumulation in the soil and water supply (Valkó et al. 2014a). This highly
diverse mosaic pattern of alkali marsh habitats considerably increases the landscape-scale
species and habitat diversity. Patches of alkali marshes usually co-occur with alkali meadows
(with
Alopecurus pratensis, Beckmannia eruciformis
and
Glyceria fluitans
ssp.
poiformis
;
Deák et al. 2014), freshwater marshes (with
Glyceria maxima
,
Phragmites australis
,
Shoenoplectus lacustris
and
Typha
spp.) and in some cases open alkali swards with
Puccinellia
spp. Based on their site characteristics and dominant species four major types of
pristine alkali marshes, can be distinguished.
3.1. Pristine Alkali Marshes
3.1.1. Schoenoplectus Marsh
Schoenoplectus
marsh is characterised by shallow water cover between spring and mid-
summer and by high salinity. The dominant species is
Schoenoplectus tabernaemontani
. The
second layer is generally formed by
Eleocharis uniglumis
.
Schoenoplectus
marsh is a species-
poor plant association harbouring only a few subordinate species, such as
Agrostis
stolonifera, Sparganium erectum
and
Symphytum officinale
(Figure 1).
3.1.2. Bolboschoenus Marsh
This widespread alkali marsh is characterised by a shallow water cover and high salt
content both in the soil and in the water. It dries out early in the year, even before mid-
summer.
Bolboschoenus
marsh form dense stands in alkali marsh systems and in the shoreline
of sodic lakes as well. The dominant monocot species are
Bolboschoenus
spp. (Hroudová et
al. 2009). Other typical species with lower cover scores include
Agrostis stolonifera, Lycopus
spp.,
Rumex palustris
and
Epilobium tetragonum
(Figure 2)
.
