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ŠUMARSKI LIST 1-2/2019 str. 41     <-- 41 -->        PDF

inversion during the most observed days in the Sovljak doline. The southerly exposed slope, with the highest value of temperature amplitude, indicates the greater amount of received solar radiation, unlike the other two measuring points in the doline where received solar radiation is restricted by the doline’s rim and northern exposition. Results of the measurements of the relative humidity are showing lower values on slopes, than at the bottom of the doline corresponding with the results of the temperature distribution.
Temperature inversion occurs as a consequence of the smaller amount of received solar radiation, caused by the geomorphology of the doline and shading from the vegetation. Whiteman et al. (2004) were studying dolines in the eastern Alps (Austria) during calm, clear-sky conditions, and concluded that the sky-view factor is the most important topographic parameter determining minimum temperatures in dolines of different geometry, as a result of concave topography reducing the view of sky. While studying Viljska ponikva doline in Croatia, Antonić et al. (1997) emphasised the effect of insolation quantity, altogether with the tree canopy shading, and doline altitude on the topoclimate.
Due to the presence of temperature inversion, normal vertical temperature gradient in the Sovljak doline is modified, resulting in increased and negative value. It amounts to approximately -5 °C/100 m, that is 8 times higher than the normal value, which usually amounts to 0.6 °C/100 m (Šegota and Filipčić, 1996). Polli (1961) observed similar phenomenon in the dolines of the Province of Trieste (Italy), where he recorded as much as 12 times higher temperature gradient inside the doline, compared to its surroundings.
Flora – Flora
Altogether 107 taxa (98 species, 2 subspecies and 7 taxa identified only to the genus rank) were recorded in the flora of the Sovljak doline (Tab. 2). Taxa identified only to genus rank were excluded from some analyses. There were 97 taxa belonging to spermatophytes, while 10 taxa were pteridophytes. The largest group were dicots with 80 taxa, followed by monocots with 16 taxa, and conifers with one taxon. The recorded taxa belong to 50 plant families, out of which the most represented were Lamiaceae (10.28 %), followed by Brassicaceae (5.60 %) and Ranunculaceae (5.60 %), while other families account for less than 5 % each.
It is well known that karst dolines, due to specific habitat conditions they provide, have a great potential to preserve relicts, endemic, mountain and wet-woodland species, and also represent an important source of knowledge about vegetation history (Bátori, 2012). The Sovljak doline showed the capacity of preserving endemic taxa (Cardamine kitaibelii, Cardamine waldsteinii, Helleborus niger and Polystichum × illyricum), and also included a few species threatened according to the IUCN Red List (Tab. 2).
The phytogeographical spectrum of the Sovljak doline showed the predominance of Eurasian floristic element