Variability and Evolution, 1993, Vol. 2/3: 103–112
ANDRZEJ NIENARTOWICZ, JADWIGA WILKON-MICHALSKA
Institute of Biology,
Nicholas Copernicus University, Torun,́ Poland
THE APPLICATION OF NUMERICAL ANALYSIS TO COMPARISON OF ECOLOGICAL AMPLITUDES OF HALOPHYTIC
SPECIES1
NIENARTOWICZ A., WILKON-MICHALSKA J. 1993. The application of numerical analysis to comparison of
ecological amplitudes of halophytic species. Variability and Evolution, Vol. 2/3: 103-112, Figs. 4, Adam
Mickiewicz University, Faculty of Biology, Poznan.´
Abstract. Detrended correspondence analysis of Polish halophytic communities revealed
environmental salinity as the main gradient in their structural differentiation. The quantitative
occurrence of 20 halophytes along this gradient has been computed and compared. The
possibility of infraspecific differentiation of these species was considered on the basis of their
position on a two dimensional ordination diagram and of their environmental amplitude patterns.
Key words: clinal variation, correspondence analysis, environmental gradient, halophytes,
ordination
Introduction
Description of the habitats is frequently needed as a basis for hypotheses and
further research in the study of behaviour of halophytic species in relation to important ecological factors. According to Haeck et al. (1985) such descriptions could
be based on a number of existing phytosociological tables covering most of the
1 Study
carried out within the Project CPBP 04.10.01
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plant communities occurring in saline habitats. Every such table with its synoptic
information on the species composition of the plant community is taken as a unit
of observation which can be interpreted on the basis of the general synecological
knowledge of the communities (Westhoff, den Held 1969; Haeck et al. 1985).
In the study of clinal variation of plant communities, i.e. the variation along an
environmental or geographical gradient (Gould, Johnson 1972), numerical ordination
methods, besides numerical classification methods and direct gradient analysis, are
commonly used (Jardine, Sibson 1971; Gauch 1982). These methods order the phytosociological units according to their complete species composition in the phenetic
space, and by comparison with the ordination in ecological space they could explain
the influence of the environment on the differentiation of communities (Feoli, Ganis
1984).
The phytosociological data, rearranged by ordination, could also be used to indicate the amplitude and the highest occurrence of the species in relation to important
environmental factors. Such a method has been recently developed by Haeck et al.
(1985) for the evaluation of the phytosociological and environmental amplitude of
Dutch coastal species, including those from saline habitats.
The computer programs which are commonly used by ecologists order both syntaxonomical units or relevés and the species for the sets of phytosociological tables.
The results of halophytic communities ordination were presented in a separate paper
(Wilkon-́Michalska, Nienartowicz, in press) whereas the present paper deals with
species ordination, ecological amplitudes along salinity gradient and maximal occurrence in relation to salinity for obligatory and facultative halophytes. These species have been compared with respect to these characters with indifferent halophytes,
which achieve high frequency also in communities of arable and ruderal vegetation.
Materials and methods
102 phytosociological tables containing 579 relevés and 387 species were processed. 14 of the tables contained only one relevé. The mean and maximal number
of relevés in tables were 7 and 20 respectively. The tables include the whole range
of vegetation types in saline environments in seven regions of Poland: the Baltic
coast, Szczecin Lowland, Wielkopolska, Kujawy, the area near Łe˛czyca, the lower
Nida valley, and the area near Cracow. Syntaxonomical status of 89 tables was
defined. They comprised 18 associations and 5 types of communities belonging to
6 classes in the classification system of Polish plant communities according to Matuszkiewicz (1982).
´
The relevés were compiled by Cwiklinśki (1977); Da˛browska, Swieboda (1977);
Jackowiak (1982, 1983); Jasnowski (1962); Ma˛dralski (1954); Mirek, Trzcinśka-Tacik (1981); Olaczek (1963); Piotrowska (1974); Trzcińska-Tacik (1988); Wilkon-́Michalska (1957, 1963, 1970, 1976). Most of the relevés represent communities of the
The application of numerical analysis
105
primary habitats of halophytes, where the occurrence of such species is connected
with sea-water, saline and sulphurous springs or a lode of salt. The relevés from
Wielkopolska and the area near Cracow and part of the relevés from Kujawy were
executed in habitats strongly modified by man: in the neighbourhood of salt mines,
soda factories and along the roads where salt is used for thawing snow during winter.
Detrended correspondence analysis (DCA) was used as an ordination technique.
Calculations were made with the use of a Riad 32 computer and programs from
DECORANA package (Hill 1979). For each species in the tables the cover coefficient, “Dekungswert” according to Braun-Blanquet (1951) was calculated as their
relative abundance.
DCA is an improved eigenvector ordination technique based on reciprocal averaging (RA), which was developed by Hirschfield (1935) and Fisher (1940) and
adapted for phytosociology by Hill (1973). In this method two main faults of RA
are corrected, namely the arch effect and compression of the first-axis ends relative
to the axis middle (Gauch 1982). Technical details of DCA can be found in Hill
(1979) and Hill, Gauch (1980).
To obtain a characterization of the phytosociological amplitude the first ordination axis was divided into an arbitrarily chosen number of equal sections. Subsequently, histograms for each species were constructed on the basis of the mean
cover coefficient values for that species per section of the axis. The average values
were computed only for those tables in which the species under consideration was
present.
Results
Ordination of species
Figure 1 presents the distribution of 40 species, including obligatory and facultative halophytes and those indifferent halophytes which are distinguishing species
for lower syntaxonomical units along the first two axes. The main gradient represented by the first axis can be interpreted ecologically as salinity gradient, ranging
from most saline to near non-saline habitats. Salicornia patula connected with high
salinity is placed on the left side of the diagram, whereas facultative halophytes,
viz. Bulboschoenus maritimus and Schoenoplectus tabernaemontani, and two indifferent halophytes, Sonchus paluster and Archangelica litoralis, lie near the right
end of the gradient. These four species were recorded in aquatic plant communities.
The other obligatory halophytes are scattered along the salinity gradient. Among
obligatory halophytes Juncus gerardi from less saline habitats has an extreme position at the right end of the gradient, where the points representing facultative and
indifferent halophytes are concentrated.
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The phase of succession was found to be the second major factor causing the
differentiation of Polish halophytic communities. On the diagram it is represented
by axis 2. The species from pioneer vegetation are concentrated in the upper left
hand part of the scatter diagram, whereas the species from mature communities
Fig. 1. The ordination of 40 halophytes according to salinity and succession phase
Ahs – Atriplex hastatum var. salinum, Ag – Alopecurus geniculatus, Ae – Arrhenatherum elatius, Al – Archangelica litoralis, Ao – Althaea officinalis, At – Aster tripolium, Ba – Bryum argenteum, Bc – Blysmus
compressus, Bm – Bulboschoenus maritimus, Br – Blysmus rufi, Cd – Carex distans, Chg – Chenopodium
glaucum, Cp – Centaurium pulchellum, Fa – Festuca arundinaecea, Gm – Glaux maritima, Jc – Juncus
compressus, Jg – Juncus gerardi, Lp – Lolium perenne, Lr – Lepidium ruderale, Lt – Lotus tenuifolius, Md – Matricaria discoidea, Mdn – Melilotus dentatus, Pa – Potentilla anserina, Pav – Polygonum aviculare, Pc – Plantago coronopus, Pd – Puccinellia distans, Ph – Pottia heimii, Phc – Phragmites communis, Rs – Ranunculus
sceleratus, Sap – Sagina procumbens, Sp – Salicornia patula, Spal – Sonchus paluster, Ss – Spergularia
salina, St – Schoenoplectus tabernaemontani, Sv – Samolus valerandi, Tf – Trifolium fragiferum, Tm – Triglochin maritimum, Tp – Triglochin palustre, Zp – Zanichellia palustris subsp. pedicellata
The application of numerical analysis
107
Fig. 2. Distribution of species from 16 classes and position of obligatory halophytes and Puccinellia distans along the most saline part of the gradient. Circles with the radius equal to 30 units on both axes are
drawn around some species. The notations of letter symbols: A – Bidentetea tripartiti, B – Isoëto-Nanojuncetae,
C – Chenopodietea, D – Secalietea, E – Plantaginetea majoris, F – Artemisietea, G – Littorelletea, H – Phragmitetea, I – Asteretea tripolium, J – Sedo-Scleranthetea, K – Molinio-Arrhenatheretea, L – Festuco-Brometea,
M – Scheuchzerio-Caricetea fuscae, N – Nardo-Callunetea, O – Trifolio-Geranietea sanguinei, P – QuercoFagetea. The notations of species as in Fig. 1
including also tree species are placed in the lower right hand corner of the diagram.
The species from meadow communities occur in the middle of the structural gradient. Generally, the species are concentrated in similar places (in relation to the
two main gradients) as the syntaxonomical units to which they belong (Wilkon-́Michalska, Nienartowicz, in press).
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A. Nienartowicz, J. Wilkoń-Michalska
Fig. 3. Obligatory halophytes and Puccinellia distans histograms along axis 1, showing the mean cover coefficient for the tables containing the species concerned. The number of tables containing the species is written
above the histogram. The number of tables per section is indicated below the lowest histogram
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109
Fig. 4. Histograms of some facultative and indifferent halophytes. The meaning of numbers as in Fig. 3
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A. Nienartowicz, J. Wilkoń-Michalska
Near the left end of axis 1 related to the most saline environments occur mainly
species from the classes Chenopodietea, Artemisietea and Plantaginetea majoris.
Species belonging to these syntaxa are located at the shortest distance from obligatory halophytes, within a radius of 30 units on the two axes (Fig. 2).
Obligatory halophytes, excluding Atriplex hastatum var. salinum, reach similar
value on axis 2. No species occur near Salicornia patula, and 6 species from 3
classes are placed inside circles drawn around Spergularia salina and Triglochin
maritimum.
Weed pioneer species from Bidentetea are concentrated in the left part of axis
1 but in the upper part of the diagram. In Figure 2 species from the classes Molinio-Arrhenatheretea, Festuco-Brometea and Querco-Fagetea are scattered progressively from the left to the right lower part of the diagram.
Comparison of ecological amplitudes of some species
The ecological amplitude of Salicornia patula is the narrowest among the seven
compared obligatory halophytes (Fig. 3). This species reaches the maximal values
of cover coefficient in most saline habitats. Four other obligatory halophytes, viz.
Spergularia salina, Atriplex hastatum var. salinum, Glaux maritima, Triglochin maritimum and Puccinellia distans, which could be classified as facultative halophytes,
occur in a wide range of syntaxonomical units from salt-marshes to Scirpetum maritimi. They were only occasionally found in associations with extreme positions in
our ordination model.
Figure 3 clearly shows the similar positions of maximal cover coefficients
of Atriplex hastatum var. salinum and Puccinellia distans on the salinity gradient.
The ecological amplitude of Juncus gerardi, which occurs especially in coastal meadows, is narrow and its optimum corresponds to a high value on axis 1.
Other facultative and indifferent halophytes, excluding Pharagmites communis
and Agrostis stolonifera, reach lower values of cover coefficient than the obligatory
ones (Fig. 4). Among them Plantago major, Festuca rubra and Leontodon autumnalis have their optima in very saline habitats, whereas Samolus valerandi, Agrostis stolonifera and Phragmites communis in less saline aquatic environments. The
positions of species from aquatic communities in the two-dimensional ordination
diagram are related to the distribution of points representing Junco-Samoletum valerandi, Scirpetum maritimi and Son-cho-Archangelicetum litoralis on the syntaxonomical units ordination model (Wilkon-́Michalska, Nienartowicz, in press).
Figure 4 shows that Samolus valerandi and Festuca rubra have narrow amplitudes, and Phragmites communis a very wide one. According to the amplitude pattern and the position of the maximal cover coefficient, the differences between the
other species presented in the figure are rather small. These species occur especially
The application of numerical analysis
111
in the semi-saline meadow communities. Among them only Potentilla anserina
has three centres along the salinity gradient.
Conclusions
It may be concluded that the same ecological factors which cause the structural
variation of Polish halophytic communities have been detected in gradient analyses
of communities and species from saline habitats in other geographical regions. Haeck
et al. (1985) ordered Dutch coastal communities using RA method and found salinity
to be the second gradient, and the structural complexity of vegetation which is
related to the phase of succession, to be the fourth.
Salinity was also found to be the main environmental factor differentiating the
structure of vegetation in the study of halophytic communities in Kujawy with the
use of direct gradient analysis (Wilkon-́Michalska 1963). In that study the soil salinity measured in Salicornietum patulae, Puccinellio-Spergularietum saline, Triglochino-Glaucetum maritimae and Scirpetum maritimi was 3.69, 0.94, 0.71 and
0.52 g Cl– per 100g of soil, respectively. The values of other environmental factors,
such as pH and soil moisture, are not correlated with the position of these communities along the first axis.
The ordination model and amplitude patterns in this paper could be the starting
points for further research within the framework of a multidisciplinary study of
halophytic species in relation to the characteristics of their habitats, as well as for
taxonomical research. In the study of halophytes in Kujawy (Wilkon-́Michalska
1963, 1976), infraspecific differentiation and ecotypic variation especially among
obligatory and facultative halophytes were observed. The histograms constructed on
the basis of the existing phytosociological data show that also indifferent halophytes,
such as Phragmites communis, Agropyron repens, Potentilla anserina, Plantago
major and Leontodon autumnalis, which have a wide ecological amplitude and few
centres along the main gradient, could occur as different infraspecific taxa in the
communities under consideration.
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