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ŠUMARSKI LIST 5-6/2014 str. 17     <-- 17 -->        PDF

lines 8 & 11, quercetosum pubescentis and quercetosum petraeae, respectively) as assigned by the same author (Horvat 1959). Furthermore, it is still an open question whether or not stands of the association Querco pubescenti-Carpinetum in NW Adriatic represent zonal vegetation type or only a secondary succession stage of forest stands of the association Aristolochio luteae-Quercetum pubescentis. We are inclined to accept the second scenario and treat studied stands of the association Aristolochio luteae-Quercetum pubescentis as a zonal vegetation type of the research area. Results of our preliminary analyses additionally pinpoint the need of a thorough synsystematic revision which will result in a more stable classification scheme in Croatia.
Studied stands are completely isolated from other forests; tectonic dolines, enclosed by precipitate walls within non-forest, petrophytic and scarcely developed vegetation types with low coverage, appear as green islands shaped by specific microclimatic conditions of the dolines. Of considerable interest and in light of vegetation succession processes, are fragmented stands with large-leaved lime (Tilia platyphyllos) bellow the precipited walls of the eastern flank of Vitra. Similar stands are developed on steep calcareous slopes some 500 m above the tectonic dolines and most probably represent an advanced succession stage after deforestation of stands of the association Aristolochio luteae-Quercetum pubescentis. Stands whith large-leaved lime from close vicinity were already mentioned by Horvat (1962) and Vukelić et al. (2006, 2007), who classified them into a subassociation Calamagrostido-Abietetum tilietosum platyphylli and association Ostryo-Abietetum (though with abundand Tilia cordata in a shrub layer), respectively, while Accetto (1991), Dakskobler (2004) and Košir and Surina (2005) classified similar stands with Tilia platyphyllos from the Čičarija range into the associations Corydalido ochroleucae-Aceretum (on calcareous boulders on northern slopes of Čičarija range, southwestern Slovenia), Ostryo-Quercetum pubescentis var. geogr. Anemone trifolia tilietosum platyphylli (from the central Soča valley in western Slovenia) and Paeonio officinalis-Tilietum platyphylli (on flysch belts within limestone slopes exposed to south, Čičarija range, southwestern Slovenia), respectively, as long-lasting succession stages or even azonal vegetation types. Nevertheless, according to our observation, neither of afore mentioned syntaxa suits the topology of stands with large-leaved lime in the proximity of studied stands.
Despite great overall similarity in floristic composition, structure, as well as homogeneity in number of taxa per relevé of stands of both tectonic dolines (Table 2), ANOSIM detected statistically significant differences (though based on rather low number of samples per group), which are well reflected in Fig. 3A. Ulmus minor, Tilia platyphyllos and Sorbus domestica appear to contribute most to the differences by means of their exclusive occurrence (U. minor) or higher frequency and coverage (T. platyphyllos and S. domestica) in the tectonic doline Vitra.
Well sheltered by precipitate walls and hard to access, forests in tectonic dolines Pihlja and Vitra represent preserved (remnant) stands with no visible traces of wood exploitation. Nowadays they represent protective forest stands of high scientific importance, giving valuable insights in patterns, processes and dynamics of northern-Adriatic vegetation and as such are in need of a thorough protection.
Forest stands developed in tectonic dolines Pihlja and Vitra, located within steep, calcareous slopes between 260 and 470 m above sea level above Drivenik in Vinodol valley, represent zonal forests of the association Aristolochio luteae-Quercetum pubescentis. Floristically and structurally homogenous stands host a moderate number of vascular plants per plot (Me=25, CV=9,3 %) and cover 1,75 and 2,73 ha, respectively (85 and 70 % of tectonic dolines, respectively). Studied stands are floristically most similar to stands of the association Aristolochio luteae-Quercetum pubescentis from NE Italy, Slovenia and NW Adriatic and subassociation Querco-Carpinetum orientalis lauretosum from Istrian Peninsula. Multivariate analyses pinpointed on several incongruences in current synsystematic schemes and forest topology within the alliance Ostryo-Carpinion orientalis and a need for a thorough revision. Unsettled synsystematics makes addressing the forest vegetation zonation of the area uncertain, but we nevertheless assume that stands with Carpinus orientalis (i.e., Querco pubescenti-Carpinetum orientalis) represent only secondary succession stages in various thermophytic vegetation types and do not represent zonal vegetation in northwestern Adriatic. Studied forests in tectonic dolines Pihlja and Vitra represent well preserved forest stands without any visible traces of wood cutting and are valuable in giving insides into patterns, processes and dynamics of northern-Adriatic vegetation. As such they are in need of special protection.
Author thanks Mitja Zupančič (Slovenian Academy of Sciences and Arts, Ljubljana), Joso Vukelić and Irena Šapić (Faculty of Forestry, University of Zagreb) for valuable discussions, while Borut Kružić (Natural History Museum Rijeka) helped in preparation of Fig. 2. Joso Vukelić and Irena Šapić provided author also with extensive synoptic tables used for comparative analyses. Željka Modrić Surina commented on previous version of the manuscript. The research was financially supported by the Public Institution »Priroda« (project no. 112-07/13-02/01–2170-52-02/3-13-21).