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POLISH JOURNAL OF ECOLOGY
(Pol. J. Ecol.)
53
4
591–595
2005
Research note
Monika SPOREK, Agnieszka ROMBEL-BRYZEK
University of Opole, Department of Ecology and Nature Conservation,
Kominka 4, 45-035 Opole, Poland,
e-mail: [email protected]
WETLAND RESTORATION ENHANCES THE DEVELOPMENT OF
PROTECTED SPECIES IRIS SIBERICA L.  A CASE STUDY
ABSTRACT: The diminution of biological
diversity is widely observed throughout the world
in a variety of plant communities. Species protection itself is an insufficient form of preservation
of the Siberian Iris population. A serious threat
to this species is systematic diminishing of its typical habitat – Molinietum caeruleae plant community, i.e. Molinia meadows on calcareous, peaty or
clayey-silt-laden soils. Its maintenance is possible
only through conservation and restoration of the
plant communities in which it occurs.
KEY WORDS: Iris siberica, population
study, wetland
In Poland the Siberian Iris (Iris siberica
L.) is a plant under strict legal species protection, with a requirement for active conservation (Rozporządzenie... 2004). In the
Polish Red List of threatened plants it is labelled with signature V (Vulnerable) – which
means that the species is moderately declining (Z arzyck i and Sz el ąg 1992). A serious threat to this species is diminishing of its
typical habitat – Molinietum caeruleae Koch
1926 plant community, i.e. Molinia meadows
on calcareous, peaty or clayey-silt-laden soils
(Matuszk ie w icz 2001; D enisiu k 1995).
The Siberian Iris grows also in swamp alder
journal 4.indb 591
woods Ribo nigri – Alnetum, alluvial Alno –
Padion forests, and is exceptionally found in
mesotrophic parts of moist pine forests Molinio – Pinetum (Matus z k ie w ic z 1982).
Species protection itself is an insufficient form of preservation of the Siberian Iris
population. Its maintenance is possible only
through conservation of the plant communities in which it occurs. The Molinion alliance
can be found in Annex I to the Habitat Directive (Council Directive 92/43/EEC of 21 May
1992 on the Conservation of Natural Habitats
and of Wild Fauna and Flora; Council Directive 97/62/EC of 27 October 1997 adapting
to technical and scientific progress…). In
order to protect this plant associated areas
in which it grows should be included in the
net NATURA 2000 as Special Areas of Conservation (SACs). The European system of
habitat classification attributed code 6410
to Molinia meadows on calcareous, peaty or
clayey-silt-laden soils (Molinion caeruleae)
(Devillers and Devillers-Terschuren 1996;
Interpretation Manual of European Union
Habitats 2003).
Molinia meadows, where the Siberian
Iris occurs, are connected with extensive agriculture. These meadows, not fertilised or
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Monika Sporek, Agnieszka Rombel-Bryzek
sown, and mown once a year in late summer,
are conspicuous for their unusual floristic
value. The traditional form of management
favoured the development of a characteristic composition of species, which resulted in
a floristically rich and colourful plant community.
At present Molinia meadows are a rather
rare element of flora. Considering them as
non-agricultural sites, the cessation of the
traditional management, afforestation, and
the drainage are the main factors leading
to a reduction of their area and disappearance of the valuable plant species occurring
Table 1. Individual characters in the population of Iris siberica L. under study.
Value
Character
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Standard deviation
Variation coefficient
[%]
min
max
mean
Height
of flowering
plants
[cm]
25.5
129.0
77.27
17.8
23
Length
of inflorescence
[cm]
6.0
36.0
16.58
6.60
40
Number
of flowers
[number]
1.0
7.0
3.71
1.27
34
Length
of leaves
[cm]
26.0
89.0
52.18
13.82
26
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Wetland restoration…
here, not only the Siberian Iris. That is why
the World Conservation Union (IUNC) includes humid and wet meadows among the
most threatened habitats of Europe (D eni siu k 1995). Because of the elimination of
flooding, intensive land drainage, and changes to arable grounds (B ek ker 1989, G arc i a
1992), such habitats became extremely rare.
A considerable part of their characteristic
flora became classified as central European
species under protection (S chnitt ler and
Günt her 1999). In upper Rhine, as well as
in the valleys of the Elbe and Danube in Germany, a large scale restoration of wet meadows with a variety of their plant species has
been undertaken (Höl z er and O tte 2003).
Our research were focused on the study
of population dynamics and biometrical
analysis of the Siberian Iris (Iris siberica
L.). A meadow situated on foothills in
the southern part of Poland (Kaczawskie
Foothills, 51º27’ N, 16º20’ E) was selected
as the study area. The whole complex of
meadows extends to an area of 100 ha
being crossed with numerous drainageditches. Nie w i adoma (1997) mentions
that before the drainage performed in
1992, the highest abundance of Siberian
Iris in the region and one of the highest
in Poland was noted in this area. Due
to drainage of the habitat the Siberian
Iris population survived only in the eastern part of the meadow, covering an area
of about 20 ha. In 1997 Nie w i adoma
(1997) recorded 280 clumps. However in
the year 2001 – 1064 clumps of Siberian
Iris were found in this area. This means
that since 1997 the population increased
almost four times. Moreover, the clumps
were growing mostly along drainageditches. The most probable reason of such
a considerable increase in numbers of the
Siberian Iris was an improvement of moisture conditions. In 1994 the cessation of
agricultural management of the meadows
by a local state-owned agricultural farm
took place, as well as the maintenance of
drainage-ditches. It caused an increase in
soil moisture which in turn resulted in the
expansion of the Siberian Iris population.
This is in accordance with the observations of Cabała and others (C ab ał a et al.
1996), who pointed at high requirements
journal 4.indb 593
593
of Siberian Iris in relation to moisture
conditions of habitat.
For analyses of individual features five
clumps were chosen at random. They comprised 133 blooming individuals and 566
without flowers. The share of young plants,
not blooming (in vegetative phase) in the
population was 81%, while in the case of
blooming individuals (in generative phase) –
only 19%; so the proportion between phases
was 4:1.
The biometrical analysis comprised only
blooming individuals. All the measurements
were taken in a period of full blooming of
the studied population, i.e. in the second
half of June. The following individual
features were measured to the nearest 1 cm:
the height of plants (of the inflorescence
shoots) and the length of inflorescences. All
flowers in each inflorescence were counted.
Additionally, the length of 10 leaves chosen
at random from each previously selected
clump was measured.
Based on the biometrical measurements
one can state that the individuals of studied population were in good condition. The
measured values of plant height ranged from
25.5 to 129.0 cm (Table 1). A large number
of shoots exceeded 1m, and the number of
flowers in an inflorescence was 4, on average. The mean length of inflorescences of the
studied population was 17 cm. It seems that
not only the density of clumps in the study
area (~ 20 ha) increased since 1997 but the
individual status of plants indicates favourable conditions for their growth.
The soil samples were taken from
the rhizosphere layer i.e. from a depth of
20–30 cm in the close vicinity of clumps.
The obtained values of pH ranged from 4.73
to 5.80. The soil was qualified as slightly
acidic to acidic (Gli ńsk i 1999). Lub ow icka (1984) states that the optimum range
of pH for Siberian Iris is between 5–7. According to Cabała and others (C ab ał a et al.
1996) this species prefers slightly acidic soils,
whereas Fij ał kowsk i (1994, 1995) gives
pH value 6.6. Hence, the obtained results are
consistent with these data, however, it seems
that slightly acidic soil is more favourable
for the growth of Siberian Iris; it is indicated
by the greater height of individuals in such
places.
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Monika Sporek, Agnieszka Rombel-Bryzek
Beside the Siberian Iris two other rare
plant species were also found, that is the
Broad-leaved Marsh Orchid (Dactylorhiza
majalis (Druce.) Soo.), and the Common
Gladiolus (Gladiolus imbricatus) – both species are strictly protected by the Polish law
(Rozporządzenie… 2004).
The conclusions from the research are:
– Due to land melioration of humid and
wet meadows carried out in the 90’s, the population of Iris siberica L currently occupies
only 1/5 of the previous habitat (~20ha).
– However the natural conditions for this
type of habitat (Molinietalia), (light acidity,
higher humidity) even on such a small area
resulted in the increase of Iris siberica density
and good condition of individuals.
– It seems that even insignificant wetland
patches in the rural area with extensive agriculture, may be adequate to support refugees
of many species as presented on the example
of Iris siberica L.
– Molinietum caeruleae i.e. Molinia
meadows on calcareous, peaty or clayeysilt-laden soils are hot spot of biodiversity
in the landscape of Poland, and species Iris
siberica L. can be used when selecting protected areas.
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(Received after revising July 2005)
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