Standardnom metodom srednjoeuropske fitocenološke škole (Braun-Blanquet 1964) istražena je i opisana nova asocijacija bukove šume s dugolisnom naglavicom – Cephalanthero longifoliae-Fagetum ass. nova, koja se rasprostire u kolinsko-submontanskom pojasu panonskoga gorja sjeverne Hrvatske, na visinama od 200 do 700 m, na lesnim i romboidnim naslagama povrh kojih se najčešće nalazi luvisol. Obilježava ju relativno siromašan i homogen florni sastav, izostanak brojnih vrsta ilirske sveze Aremonio-Fagion (Horvat 1938) Borhidi in Törek, Podani et Borhidi 1989, izrazita prevlast vrsta Festuca drymeia i Carex pilosa te stalnost vrsta srednjoeuropskih bukovih šuma. Svrstana je unutar srednjoeuropske sveze Fagion sylvaticae Laquet 1926. U odnosu na sastav ostalih bukovih šuma iste sinsistematske pripadnosti ističu se dijagnostičke vrste Festuca drymeia, Polystichum setiferum, Cephalanthera longifolia, Rubus hirtus, Tilia tomentosa, Potentilla micrantha i Ruscus hypoglossum.
U radu je prikazano 15 novih i 137 već objavljenih fitocenoloških snimaka, na osnovi kojih je analizirana građa, sociološki i sintaksonomski karakter asocijacije Cephalanthero longifoliae-Fagetum te odnos prema srodnim asocijacijama na južnom i jugozapadnom rubu Panonske nizine i u susjednim područjima.A new association of beech forest with Sword-leaved Helleborine – Cephalanthero longifoliae-Fagetum ass. nova was described in the colline-submontane belt of northern Croatia, on the south-western edge of the Pannonian Plain. The method of the Central European Phytocoenological School (Braun-Blanquet 1964) was used in the research. Statistical comparison was performed by using programs TURBOVEG (Hennekens & Schaminée 2001) and PRIMER 6 (Clarke & Gorley 2001). MDA and UPGMA methods were made by use of Bray-Curtis similarity index. The association was presented on the basis of 15 new and 132 already published phytocoenological relevés (Table 1). In Table 2 and Figure 3 the association Cephalanthero longifoliae-Fagetum was compared with the related beech forests of the Illyrian floristic province (north-western Croatia, eastern Slovenia, northern Bosnia), then with the Central European association Galio odorati-Fagetum from the colline-submontane positions of Austria and southern Germany, and finally with beech forests of the Carpathian part of Romania.
The association Cephalanthero longifoliae-Fagetum is distributed at altitudes from 200 to 700 m, with terrain inclinations usually ranging between 10 and 20 degrees. It grows in the temperate climate with average temperatures from 9.5 to 10.7 °C and average rainfall from 800 to 1,100 mm. The parent bedrock is made up of loess and rhomboid layers generally overlaid with luvisol in a humus-accumulative horizon of medium acidity (pH about 5). The association is characterized by a relatively poor and homogeneous floristic composition, the absence of numerous species of the Illyrian alliance Aremonio-Fagion (the associations Hacquetio-Fagetum, Lamio orvalae-Fagetum, Vicio oroboidi-Fagetum), the distinct prevalence of the species Festuca drymeia, Carex pilosa and Rubus hirtus, and the constancy of the species of Central European beech forests from the alliance Fagion sylvaticae and the order Fagetalia (Figure 2). Species of warmer and drier sites occur in moderate quantities.
A synhorological analysis of the investigated association (according to Poldini 1992) gave the relatively expected results. Of the 206 species, 77 % belong to the widely distributed floral geoelement which does not characterize the southern edge of the Pannonian Plain in any particulars (cosmopolitan, circumboreal, Eurasian, Euro-Siberian, European, Mediterranean-Atlantic and others). In relation to beech forests of the Dinaric region, the studied stands completely lack the Illyrian and south-eastern European species that are important for the alliance Aremonio-Fagion, such as Rhamnus alpinus ssp. fallax, Geranium nodosum, Stellaria nemorum ssp. glochidiosperma, Scopolia carniolica, Euphorbia carniolica, Calamintha grandiflora, Omphalodes verna, and Hacquetia epipacis. The species Cardamine trifolia, Cardamine enneaphyllos, Cardamine kitaibelii, Cardamine chelidonia, Lamium orvala, Vicia oroboides, Aposeris foetida, Aremonia agrimonoides, Epimedium alpinum and Helleborus odorus were recorded individually and sporadically only on the edges of the range and in the boundary region with the communities of the Illyrian character. Only Ruscus hypoglossum and Cyclamen purpurascens are more constant in the entire range of the studied association. A large number of earlier works, especially those taken from the overview composed by an international team of phytocoenologists (Marinček et al. 1993), allow for the conclusion that the community Cephalanthero longifoliae-Fagetum lacks the diagnostic species of the Illyrian alliance Aremonio-Fagion and its sub-alliances, on the basis of which it could be subordinated to them.
According to these data and the analysis in Tables 1 and 2, these stands should be classified into the Central European alliance Fagion sylvaticae. The differentiating species towards the association Galio odorati-Fagetum and other Central European associations of the sub-alliance Galio odorati-Fagenion include Festuca drymeia, Polysichum setiferum, Cephalanthera longifolia, Ruscus hypoglossum, Rubus hirtus, Tilia tomentosa, Fraxinus ornus, and Potentilla micrantha.
Investigations into the internal structure of these beech stands revealed the local dominance of the facieses of the species Carex pilosa and Festuca drymeia, but in over 60% of the cases they were recorded together. In addition to these two, another very important species in the diagnostic sense is Cephalanthera longifolia, which gave the association its name. This is a warmth-loving species of moderately acid to basic, predominantly dry sites, generally distributed in the colline and montane vegetation belt. Most phytocoenologists classify it into the sub-Mediterranean – Euro-Asian species. Sociologically, it belongs to the class Querco-Fagetea with a mild tendency towards the communities of the order Quercetalia pubescentis. The differentiating species Tilia tomentosa and Potentilla micrantha, with the centre of their distribution lying in the south-eastern part of Europe, are particularly important for the association. This stresses the transitional character of the association (see Figure 1).
These investigations greatly contribute to the knowledge of the forest vegetation of Croatia and the boundary region of the Illyrian floristic province. The studied beech forests cover about forty thousand ha in Croatia. They have been described under the following names: Carici pilosae-Fagetum (Pelcer in: Cestar et al. 1983, Rauš et al. 1992, Trinajstić and Franjić 1999, Vukelić and Baričević 2002, 2003, Trinajstić 2007, Vukelić et al. 2007), partly under the name of Festuco drymeiae-Fagetum (Baričević 2002, Škvorc 2006, Škvorc et al. 2011, G. Horvat 2011, non Trinajstić and Cerovečki 2009), then as Polysticho setiferi-Fagetum (Baričević, Vukelić and Šapić 2009), while Marinček (1995) comprised them in the association Vicio oroboidi-Fagetum. The first three names were used earlier to describe the communities in other European areas (Germany, Romania, Slovakia, Italy), to which the stands from Croatia do not belong (compare Moriariu et al. 1968, Magic 1968, Ubaldi 1988, Coldea 1991, Oberdorfer 1992, Zupančič, Žagar and Surina 2000, and others), whereas the fourth community, Vicio oroboidi-Fagetum, differs from the former three by its composition and synsystematic affiliation.
On the other hand, this confirms the assumption by Willner (2002) that a new, insufficiently investigated association which is related to the association Galio odorati-Fagetum in its lower positions begins southeast of the Alpine area and the range of the association Galio odorati-Fagetum. Analogously to the understanding of the scope of the association Galio odorati-Fagetum, the newly established association Cephalanthero longifoliae-Fagetum would be relatively widely distributed on the south-western and southern edge of the Pannonian Plain and the transition to the Dinaric and Central Balkan area.
Naturally, this does not exclude the establishment of the association Galio odorati-Fagetum southeast of its clearly identified range in the southeast of Austria. In fact, according to the research currently under way, it can be assumed that its south-eastern boundary (which Willner considers unclear) lies precisely in the fresh sites well supplied with nutrients on dystric brown soils above moderately acid substrates of the submontane – montane belt of the Croatian Pannonian mountains (Papuk, Psunj, Krndija).
The synsystematic affiliation of association is:
Querco-Fagetea Br.-Bl. et Vlieger 1937
Fagetalia sylvaticae Pawl. 1928 in Pawl. et al. 1928
Fagion sylvaticae Laquet 1926
Galio odorati-Fagenion (Tx. 1955) Th. Müller 1959
Cephalanthero longifoliae-Fagetum Vukelić, Baričević et Šapić ass. nova. hoc.loco.
Nomenclature type is relevé 6 in Table 1
