Prodromus. Abstract. Ruderal communities dominated by Onopordum acanthium are encountered in those regions of Europe with a dry and continental climate.
Vegetatio 81: 107-115, 1989. © 1989 Kluwer Academic Publishers. Printed in Belgium.
107
Syntaxonomy of the Onopordum acanthium communities in temperate and continental Europe Ladislav Mucina
Department of Vegetation Ecology & Nature Conservancy, Institute of Plant Physiology, University of Vienna, Althanstrafle 14, A-1091 Vienna, Austria Accepted 12.12.1988
Keywords: Association,
Numerical
classification,
Onopordetalia, Ordination,
Phytogeography,
Prodromus
Abstract
Ruderal communities dominated by Onopordum acanthium are encountered in those regions of Europe with a dry and continental climate. Variability in the climate and local phytogeography within these regions is reflected in the floristic variability of the communities studied. A floristic cline within the communities was summarised by means of multivariate classification and ordination methods. Two associations distributed in temperate Europe and belonging to the Onopordetalia, the Onopordetum acanthii s.str, and Carduo acanthoidis-Onopordetum acanthii, were distinguished; The Carduo acanthoidisOnopordetum is varied and occurs in several geographic races and sub-races. The Onopordetum acanthii s.str, is confined to deep inner-montane valleys with a continental climate. The other Onopordum acanthium communities described from Spain belong to the Scolymo hispanici-Onopordetalia nervosi.
Abbreviations: CA = correspondence analysis; CLC = complete linkage clustering Nomenclature: Moore, D.M. 1982. Flora Europaea. Check list and chromosome index. Cambridge Univ. Press, Cambridge; for Agropyron, Atriplex, Cannabis, Matricaria and Tripleurospermum: Ehrendorfer, F. (ed.) 1973. Liste der Gef'al3pflanzen Mitteleuropas. 2. Aufl. Gustav Fischer Verlag, Stuttgart. For mosses: Frahm, J.-P. & Frey, W. 1983. Moosflora. Eugen Ulmer Verlag, Stuttgart. The names of syntaxa other than the associations with Onopordum acanthium follow the nomenclature of Mucina, L. & Maglock~, S. (eds) 1985. A list of vegetation units of Slovakia. Doc. Phytosociol., Camerino, 9: 175-200.
Source reference: The paper was presented at the Symposium no 6-45 'Distribution of plants and plant communities: recent anthropogenic changes' during the XIVth International Botanical Congress in Berlin (West). Introduction
Onopordum acanthium L. is a tall, biennial monocarpic thistle forming a leaf rosette in the first year
of its life cycle and setting flowers and seeds in the second. The species is both anemochorous and epichorous (MOiler-Schneider 1986). Like other thistles such as Cirsium vulgare, C. eriophorum,
108 Carduus nutans, C. acanthoides (Asteraceae) and Eryngium campestre (Apiaceae), it tends to colonise disturbed pastures. Onopordium acanthium is a weak competitor; availability of the regeneration gaps is imperative for the development and maintenance of Onopordum acanthium-dominated stands. It retreats quickly when the disturbance by grazing, poaching and browsing of animals or the disturbance of the sward by heavy machines ceases. Otherwise it is able to maintain a dominance community for several years (Brandes 1977a). Onopordum acanthium is well established especially in continental areas characterised by a summer-dry climate such as the Pannonian Basin, inner-Alpic basins and valleys (Braun-Blanquet et al. 1936; Braun-Blanquet 1961) and the southUcraine steppe zone (Solomakha etal. 1986; Kostil'ov 1987). Onopordum acanthium, O. tauricum and O. acaule are the only representatives of the genus in temperate Europe; most of the Onopordum species occur in the submediterranean and mediterranean regions (do Amaral Franco 1976). In most of its natural distribution area Onopordum acanthium is considered a characterspecies of the Onopordion acanthii (for diagnosis see Brandes 1977a, 1977b; Mucina 1981). Under influence of dry continental climates the species shows a broader coenologic amplitude, while in subhumid and humid temperate climates it occurs secondarily also in Artemisietalia communities (Brandes 1977b). Several Onopordum communities were described (see below). They show a great floristic variability and extensive distribution over Europe (see Seybold & Mtlller 1972). The aim of the paper is to numerically describe and interpret the variability within the complex of Onopordum acanthium communities in temperate and continental Europe in relation to geography and climate.
Materials and methods The study was based on 380 relevrs and another 9 constancy tables (the latter based on ca 140
relev6s) of Onopordum acanthium-dominated communities and communities assigned to the Onopordetum acanthii by diverse authors. The following countries are covered: Austria, Bulgaria, Czechoslovakia, Federal Republic of Germany, France, German Democratic Republic, Hungary, Italy, the Netherlands, Poland, Rumania, Spain, Switzerland, USSR (Ucraine, Byelorussia and Bashkiria) and Yugoslavia. First the relev6s from the same geographically well-defined areas (sharing a similar climate and phytogeographic history) were combined into local tables (sensu Westhoff & van der Maarel 1978) which served for the construction of an initial synoptic table. Heterogenous and incomplete relevrs (made on very large or very small sample plots) were discarded, as well as local tables composed of fewer than 5 relev6s were not considered. The synoptic table was completed by adding nine constancy tables of the Onopordum acanthium communities from literature sources and represented only by synoptic values (columns). All species in the final synoptic table were expressed in the constancy-class scale of BraunBlanquet (1964). Numerical classification and ordination were performed on the final synoptic table with the constancy-class values 1-5 as scores. The clustering strategy was a complete linkage method (CLC) based on the Similarity Ratio. The computer program used was NCLAS of Podani (1984). Ordination on the local tables collected in the synoptic table was performed by correspondence analysis CA (Hill 1974, 1979). No downweighting of rare species was carried out. Climatic data on average monthly precipitation, minimal and maximal mean monthly temperature were compiled from Mtlller (1982) for climatic stations located in the areas of origin of the local tables. Two climatic indices were computed. Gorczynski's K' for thermic continentality (e.g. Daget 1977b, p. 10) and the Emberger's pluviometric Q combining humidity and temperature character of climate (e.g. Daget 1977a, p. 88, equation 3) were computed. Both K' and Q values on the ordination plane of CA (axes 1
109 contain Onopordum acanthium as the dominant species. The Mediterranean group includes the Verbasco pulverulenti-Onopordetum from Extremadura (Rivas Goday 1964) and Avila (RivasMartinez 1975), the Carthamo lanati-Onopordetum from Salamanca and Zamora (Ladero Alvarez et aL 1983; Navarro Andr6s & Valle Guti6rrez 1984), the Carduo carpetani-Onopordetum from the provinces of Le6n, Avila, Segovia and Madrid (Llamos Garcia 1984; Rivas-Martinez etal. 1986), and perhaps also the 'Onopordetum acanthii" of Bellot Rodriguez (1966) from the mediterranean regions of Galicia. The Onopordum acanthium-rich subunit within the Onopordetum illyrici described from the surroundings of
and 2) were fitted using a Kriging algorithm (Ripley 1981 ; Jongrnan et al. 1987) and plotted by program package SURFER (Golden Software Inc.).
Results and discussion
Mediterranean Group A great number of communities dominated by various Onopordum species is found in the Mediterranean which is considered to be the developmental centre of the genus (do Amaral Franco 1976). Some of them, occurring in the 'continental' meseta of central Spain (Fig. 1)
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Fig. 1. D i s t r i b u t i o n o f Onopordum acanthium c o m m u n i t i e s in E u r o p e s u p e r i m p o s e d o n t h e U T M grid u s e d for m a p p i n g in F l o r a E u r o p a e a . E m p t y circles - w e s t e r n race o f t h e Carduo aeanthoidis-Onopordetum, full circles - e a s t e r n race o f t h e latter association, full s q u a r e s - Onopordetum acanthii s.str., stars - Carduo carpetani-Onopordetum, full triangles - Verbascopulverulenti-Onopordetum, e m p t y triangles - Carthamo lanati-Onopordetum.
110 Thessalonik6 in northern Greece (Oberdorfer 1953/1954) also shows some similarity with the group discussed. These communities, assigned to the Carduo carpetani-Cirsion (the Scolymo hispanici-Onopordetalia nervosi; Ladero Alvarez et al. 1983; see also Carthametalia lanati by Brullo & Marcen6 1985) differ markedly in species composition from the Onopordum acanthium communities of temperate Europe, which belong to the Onopordion acanthii (the Onopordetalia acanthii). The latter two can be considered to be vicariant orders (Mucina in press). Due to the great floristic differences between the Mediterranean and temperate groups of the communities, the former is disregarded subsequently, as it requires a separate study.
Temperate and Continental Group The original description of the only recognised community of this group to date the Onopordetum acanthii, was based on material from deep valleys of the Pyrenres (Braun-Blanquet etaL 1936). These locations, like the valleys of the Alps, are characterised by frequent temperature inversions and an overall continentality of the climate (Braun-Blanquet 1961; Izard etal. 1985). The Alpic localities of the Onopordetum acanthii range from the Dauphin6 Alps in France to the eastern Alps of Switzerland (Engadin) and south and east Tyrolia. Braun-Blanquet et al. (1936) also indicated the occurrence of this community in the continental regions of eastern Europe. The locations of the Onopordum acanthium communities are characterised by a dry (semi-arid to sub-humid) summer climate with high summer temperatures and cold winters. In the inner-Alpic basins the climate ranges from submediterranean (western Alps) to temperate subcontinental. As a rule, the well-developed Onopordetum acanthii occurs even in precipitation-rich western Europe in basins or broad valleys which lie in the rain shadows of adjacent mountain ranges running from north to south. These ranges form natural barriers for the precipitation-rich air masses as they move inland. Dry 'islands' are thus formed
in the basins and valleys, which house xeric vegetation complexes showing an exclave distribution in western Europe. This is true in particular for the Rhine Valley from Baden to Westphalia lying in the shadow of the Vosges, Nordpfalz and Eifel; the so called 'mitteldeutsche Trockengebiet' (e.g. Schubert & Mahn 1959; Gutte 1972; Brandes 1977a), sheltered by the Harz and Thtlringen Wald from the west; the dry north-Bohemian basins at the foot of the Kru~n6 Hory; e.g. Kolbek 1975); the extensive system of the inner-Alpic basins (Braun-Blanquet 1961) and the Pannonian Basin surrounded by the Alps from the west, the Carpathians from the north and east, and the Dinarides from the south. In these regions, the Onopordetum and other Onopordion acanthii communities occur in a vegetation complex of a submediterranean-subcontinental character which includes the Quercetalia pubescenti-petraeae, Festucetalia valesiacae, and Onopordion acanthii. In other, more subhumid, regions the Geranion sanguinei is also involved (van Gils & Keysers 1977). As shown by the synoptic table (full table and details on the sources available upon request from the author), the east-European type should be considered a separate unit, called Carduo acanthoidis-Onopordetum acanthii (So6 1947) as it differs by a large number of differential-species. Probably Centaurea solstitialis, C. calcitrapa, Anchusa ochroleuca, A. gmelinii, Echium italicum and Artemisia austriaca could also be considered as regional character-species of the Carduo acanthoidis-Onopordetum in the Balkan part of its distribution area (Slavni6 1951; Oberdorfer 1953/1954; Dihoru & Doni~ 1970; Coste 1975). Raabe & Brandes (1988) consider this type an eastern race with Carduus acanthoides (of the Onopordetum acanthii sensu lato). Also the Onopordetum acanthii s.str. (the name was preserved for the vegetation type of continental mountain valleys of the Pyrenres and the Alps) is differentiated by an own group of species. The Onopordetum acanthii s.str, is floristically most similar to the east-European race of the Carduo acanthoidis-Onopordetum (see below) as is
111
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also shown by the ordination diagram of axes 1 and 2 (Fig. 2). It is separated from the CarduoOnopordetum clearly along axis 3 of the CA ordination (not reproduced). Onopordum acanthium can be considered a regional character-species of the Onopordetum acanthii s.str, in the inner-mountain valley localities, but it also has high diagnostic value in the Carduo acanthoidis-Onopordetum in the continental lowland regions of eastem Europe (perhaps as a weak character-species). Its fidelity to the Carduo acanthoidis-Onopordetum is more pronounced at the edges of its distribution, e.g. in northwestern Europe (Brandes 1977a). The other character-taxa of the Onopordetum acanthff s.str. are Carduus nutans ssp. platylepis, limited to the Alpic area of the association (here having the rank of a local character-species, sensu Westhoff & van der Maarel 1978), and Onopordum acaule (limited to the Pyrenean area of the Onopordetum acanthii s.str.; cf. Braun-Blanquet etal. 1936; Braun-Blanquet 1948, p. 144). Accordingly, two geographic races can be recognised within the Onopordetum acanthii s.str., the Alpic (Carduus platylepis race) and the Pyrenean (Onopordum acaule) race (Fig. 1). The within-association variability of the Carduo acanthoidis-Onopordetum is more complicated, as
the unit covers a wide distribution (Fig. 1), the largest of the Onopordion acanthff communities. Two races with great floristic differences were revealed by a cluster analysis (Fig. 3). The Arrhenatherum race is limited to the northern and western regions of central Europe and its distribution area lies between the Rhine River and the Polesie region in Byelorussia and Ucraine. This unit houses many species with a broad coenologic amplitude (the Artemisietea and Galio-Urticetea species), mesic species recruited
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Fig. 3. CLC dendrogram of the local synoptic tables of the Onopordum acanthium communities in Europe. W - western race of the Carduo acanthoidis-Onopordetum, E - eastern race of the latter association, D - sub-race with Malva alcea from south-west Germany, A - the Onopordetum acanthii s.str., O U T - outlying tables (of transitional or fragmentary character). For symbols see Fig. 1.
112 from the elements of the Molinio-Arrhenatheretea, elements of nitrophilous fringes (Glechometalia hederaceae) and even some semi-hygrophilous species such as those of the Convolvuletaliasepium, Lolio-Potentillion and Phragmiti-Magnocaricetea, all of which penetrate the Onopordum acanthium communities from adjacent stands. The diagnostic species of the Onopordion acanthii are replaced by Dauco-Melilotion species. A shift in the phytosociological behaviour of several species of the Onopordetalia acanthii (considered as such in southeast Europe) can be observed within the Carduo acanthoidis-Onopordetum in west Europe. The species that possess broader amplitude in south-east Europe (Onopordetalia species) became more limited to this community (and the Onopordion acanthii in milder climate areas). The group of these species includes Anchusa officinalis, Verbascum phlomoides, Reseda luteola and Echinops sphaerocephalus (see also Brandes 1977a). In general, the community varies in mesic habitats, and impoverished forms of the community with some Arction lappae species are the rule (Brandes 1977b; Mucina 1981). A general retreat as a consequence of changing management practices is also observed in many regions of central Europe (for a review see Mucina in press). Two subunits (sub-races) according to the presence of xerophilous elements can be distinguished within the western race of the community: the Malva alcea sub-race and the central race. The Malva sub-race is a local phenomenon of the upper Rhine Valley and close surroundings in south-western Germany (Baden and Schwaben). Submediterranean influence is demonstrated in this unit by presence of species such as Ballota alba, Malva alcea, Isatis tinctoria, Rhynchosinapis cheiranthos and Geranium dissectum. The central sub-race is again very varied, and covers a large area ranging from east Germany to northern Hungary and having more species able to survive harsh subcontinental winters. It is well-developed in dry regions such as the mitteldeutsche Trockengebiet, and the Pannonian Basin of south Slovakia and north Hungary, thus in the rain shadows of mountain ranges such as the Harz and Thtlringer Wald, the Alps and the Carpathians.
In contrast, the east-European race (with Xanthium spp.) is more xeric and is characterised by summer annuals of (sub)continental distribution (such as Amaranthus albus, A. blitoides, Euclidium syriacum, Atriplici-Sisymbrion species) or by some C4-assimilation grasses (Cynodon dactylon, Setaria viridis, Digitaria sanguinalis). This unit is the most species-rich within the group discussed. It is found in the south Pannonian Basin, in Transylvania, from Moldavia to the steppe regions of south Ucraine, in the Balkans and northern Italy (Hru~ka 1985; Brandes 1987). The extreme eastern area of its distribution in B ashkiria is considered to support a separate subrace differentiated by continental species such as Axyris amaranthoides, Bassia sedoides, Cirsium setosum, Dracocephalum thymiflorum and Leonurus spp. (Mirkin et aL 1986). The separation of two races within the Carduo acanthoidis-Onopordetum is also supported by an ordination of the tables belonging to this association, which shows the two races to occupy two separate geographic regions (Fig. 4). Only one table from the Ucraine geographically belonging rather to the east-European race has joined the west-European unit (Fig. 3). A characteristically low number of taxa were found in that table (Solomakha et al. 1986). The occurrence of Onopordum acanthium-dominated communities or their fragments north of the central-European mountain systems, particularly in the north-west European lowlands (Sissingh
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Fig. 4. CA ordination (axes 1 and 2) of the tables belonging to the Carduo acanthoidis-Onopordetum only. The geographic longitude (full lines) and latitude (dashed lines) are plotted. For symbols see Fig. 2.
113 12.00
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Fig. 5. Pattern of thermic continentality according to Gorczynski (K') on the ordination plane of axes 1 and 2 of the Correspondence Analysis. The interpolation method used was kriging and the plotting was carried out with program package S U R F E R (Golden Software Inc.).
1950; Westhoff & den Held 1969; Grhu etal. 1985; is supposedly of recent neophytic character (Fig. 1). Towards the east of the regions discussed, the climate has a subcontinental to continental character as is also shown by rising values of thermic continentality (Fig. 5) which favours the occurrence of a floristically rich CarduoOnopordetum acanthii. The pluviothermic coefficient of Emberger generally decreases along axis 1 (Fig. 4) towards the climatically extreme of continental Europe (Fig. 6). The highest value of Q was scored for Ancona which has a mild submediterranean climate. A similar pattern of two basic races with an opposite distribution pattern following the climatic differences between atlantic west Europe 1200
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and continental east Europe was also observed with other ruderal communities such as the Berteroetum incanae (Mucina & Brandes 1985), Malvetum neglectae (Brandes 1981), Sambucetum ebuli (Brandes 1982), Torilidetum japonicae (Mucina in press) and can be considered a rather general phytogeographic phenomenon.
Acknowledgements Data treatment was carried out and the first drafts of this paper prepared during the author's stay at the Dept of Geobotany, University of Nijmegen, the Netherlands in 1980-1981 (Fellowship in Biology) and later at the Dept of Geobotany of the
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Fig. 6. Pattern of Emberger's pluviometric coefficient (Q) on the ordination plane of axes 1 and 2 of correspondence analysis A - Ancona, B - Berlin. For further details see Fig. 5.
114
Institute of Experimental Biology & Ecology, Slovak Academy of Sciences, Bratislava, Czechoslovakia. Unpublished relev6 material as well as data from the literature were generously provided by D. Brandes, G. Coldea, J. Czaplewska, W. Forstner, P. Gutte, K. Hru~ka, I. Jarolimek, P. Julve, S. Klotz, K. KopeckS,, J. Korna~, T. Krippelovfi, W. Kunick, W. Lohmeyer, L. Markovir, A. Py~ek, A. Szab6, A. Terp6, V. Tlusthk, I. UUmann, V. Westhoff and M. ZaliberovL G. Schlosser kindly assisted with some computations. A. Szab6 and E. van der Maarel contributed helpful comments on the paper and Jo Hughes corrected the English. The financial support of the Deutsche Akademische Austauschdienst (DAAD) which made the presentation at the XIVth International Botanical Congress possible is much appreciated.
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