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Species from the order Quercetalia pubescentis Br.-Bl. (1931) 1932 in the forest vegetation of the Požega mountains

The paper is a component part of a comprehensive synecological-vegetational study of the forest vegetation of Požeška and Babja Gora. The investigated area represents the southern part of the Slavonian mountain range. It is an exceptionally valuable site in the vegetational picture of the Republic of Croatia, which is yet to be studied, described and evaluated in an adequate manner. The research confirmed the outstanding wealth and diversity of plant species and forest communities that result from their position on the boundary of highly diverse influences (the Alpine influence from the west, the Dinaric one from the south and the much more arid one from the Pannonian plain). Special focus was placed on the presence of the species from the order Quercetalia pubescentis in the forest vegetation of the Požega mountains, since they represent a unique and rare feature in continental forest ecosystems. The analysis of the floral composition of the forest communities in the studied area has confirmed a very significant presence of thermophilic elements from the order Quercetalia pubescentis in almost all forest communities. Most of these communities were detected and described in the studied area for the first time, together with some important species of the order Quercetalia pubescentis, such as the service tree (Sorbus domestica L.). A community with the highest number of species of the order Quercetalia pubescentis is a thermophilic forest of sessile oak and black pea (Lathyro-Quercetum petraeae Ht. (1938) 1958). Systematically, it belongs to the order Q. pubescentis and was described in the study area for the first time. This community takes up the warmest, predominantly southern positions in the upper parts of slopes and ridges with higher inclinations (30-35°) and shallower soils. Of a total of 109 species, the dominant ones include those from the order Quercetalia pubescentis, especially Fraxinus ornus, Sorbus torminalis, Cornus mas, Ligustrum vulgare, Lathyrus niger, Carex flacca, Dactylis glomerata, Viola hirta, Calamintha clinopodium, Mellitis melyssophyllum and others. In terms of origin and development, the community is much closer to the stands on Kalnik (Vukelić 1991) than to the stands on Samoborsko Gorje described by Šugar (1972) and those on Strahinjščica described by Regula-Bevilacqua (1978). Species of the order Quercetalia pubescentis are also significantly present in the acidothermophilic forest of sessile oak with hawkweed (Hieracio racemosi-Quercetum petraeae /Vukelić 1990/ 1991) and in the forest of sessile oak with fescue (Festuco drymeiae-Quercetum petraeae /Jank. 1968/Hruška 1974), and to a much smaller measure in the communities of sessile oak and sweet chestnut (Querco-Castaneetum sativae Ht. 1938), the Illyrian forest of sessile oak and common hornbeam (Epimedio-Carpinetum betuli /Ht. 1938/ Borh 1963), the forest of sessile oak and common hornbeam with fescue (Festuco drymeiae-Carpinetum betuli Vukelić /1990/ 1991) and beech communities. The spectre of biological forms, the spectre of floral geoelements and the mean ecoindicator value according to the Ellenberg scale (1974) were also determined for each community individually and accumulatively. The results of this work broaden the perceptions of the number, distribution and importance of the species of the order Quercetalia pubescentis in forest ecosystems of Pannonian montane area and complement the vegetational picture of the Republic of Croatia and of a wider area.

species; order Quercetalia pubescentis; forest vegetation; Požega hill area; floral composition; phytocoenological records; synecological conditions; importance

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