DIGITALNA ARHIVA ŠUMARSKOG LISTA
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|ŠUMARSKI LIST 5-6/2014 str. 10 <-- 10 --> PDF|
extrazonal vegetation type – evergreen (extrazonal) forests where zonal vegetation (at lower altitudes) is largely temperate broad-leaved. Specific microclimatic conditions due to temperature inversion in freezing dolines of the Dinaric karst resulted in extrazonally developed subalpine beech stands (Polysticho lonchitis-Fagetum) and even stands dominated by mountain pine (Pinetum mugo s.l.) or subalpine Dinaric tussocks which usually thrive on higher elevated sites, a phenomenon already studied in detail by several researchers (e.g. Krašan 1880; Beck 1906; Wraber 1949; Horvat 1953, 1961; Martinčič 1977; Surina and Vreš 2004; Surina and Rakaj 2007). Additionally, extreme climatic and edaphic conditions (e.g. periglacial deposits – screes and boulders at the bottom of dolines) in afore mentioned dolines result in development of (c) azonal vegetation types. In the NW Dinaric Alps, spruce forests (Hacquetio-Piceetum, Lonicero caeruleae-Piceetum, Laserpitio krapfii-Piceetum, Aremonio-Piceetum) by a rule, do not form (extra)zonal vegetation belts but are rather confined to dolines within zonal beech (Ranunculo platanifolii-Fagetum) or fir-beech (Omphalodo-Fagetum) forests (Horvat 1953; Zupančič 1980). Azonal plant communities are generally more strongly influenced by specific edaphic factors than by climate. For example, forest stands of the associations Ribeso alpini-Piceetum, Calamagrostido-Abietetum and Ostryo-Abietetum are developed exclusively on calcareous stone blocks and boulders (Zupančič and Accetto 1994; Vukelić et al. 2006, 2007; Vukelić 2012) within zonal fir-beech forests (Omphalodo-Fagetum). Due to human impact, natural vegetation does not exist over large regions today. It is usually reconstructed and then termed potential natural vegetation (Kovar-Eder and Kvaček 2007).
Dense forest stands developed within steep calcareous slopes exposed to south and southwest in two tectonic dolines above the Vinodol valley, Pihlja and Vitra, make a strong impression from afar (Fig. 1). Dark green forest canopies hardly emerge over the precipitate walls of the dolines and markedly stand apart from the surroundings. Vegetation cover of steep and partly precipitate calcareous slopes that surrounds the dolines represents floristically depauperate and fragmented petrophytic non-forest stands in various succession stages dominated by Drypis spinosa, Sedum ochroleucum, Peltaria alliacea, Campanula pyramidalis, Cephalaria leucantha, Satureja montana, Genista sericea, Salvia officinalis, Daphne alpina, Frangula rupestris, Rhamnus saxatilis, Juniperus sabina, Coronilla emerus subsp. emeroides, Prunus mahaleb, Carpinus orientalis and Fraxinus ornus.
Occasionally, some individual specimens of evergreen Quercus ilex and Phillyrea latifolia were observed. At first sight, forest stands in these picturesque dolines represent azonal or at least extrazonal vegetation type. Since these stands are virtually unknown to botanists, our primary goal was to investigate their floristic composition, structure, ecology and topology.
The Vinodol valley in NW Adriatic (Fig. 2) is characterized by a distinct morphology as well as complex geological structure (Blašković 1999). The Upper Palaeogene flysch deposits are found in a synclinal position of a narrow valley with a NW-SE strike and are compressed by the Lower Palaeogene and Upper Cretaceous limestones. The contacts between the flysch and calcareous rocks are mainly tectonic with a markedly developed reverse character of