VASCULAR FLORA OF THE UVAC RIVER GORGE IN SERBIA

During research on the vascular flora of the Uvac River Gorge, 730 species and infraspecific taxa from 87 families were found. The most numerous representatives were from the families Asteraceae (81 taxa), Fabaceae (57), Poaceae (55) and Lamiaceae (47). Hemicryptophytes were the dominant life form (56,6%); in the chorological sense, the most numerous were sub-Central-European (16,3 %) and Euro-Asian species (11,5 %). The following endemic species were recorded: Alyssum markgrafii, Valeriana simplicifolia, Cicerbita pancicii, Lamium bifidum balcanicum, Alyssum corymbosum, Fumana bonapartei, Euphorbia glabriflora, and Potentilla visianii. UDC 581.9(497.11)(282 Uvac)


INTRODUCTION
The Uvac River runs through southwest Serbia (Fig. 1).It arises on Mt.Ozren, 14 kilometers southwest of Sjenica and joins the Lim River at around 5 km downstream from Priboj-on-Lim.The river's source is located at 1,400 m a.s.l. and is a spring of the helocrene type; the delta is at 380 m a.s.l.Length of the Uvac River is 119 km, and area of the watershed is 1,334 km 2 .At elevations of 985-760 m a.s.l.along the stream, the river is partitioned by three dams, which make three artificial lakes (Sjeničko, Zlatarsko, and Radoinjsko Lakes).
Relief of the Uvac River watershed is characterized by very heterogeneous geological structure.The age of rocks ranges from the Paleozoic to Quaternary.Most of the area is occupied by serpentines, marl, limestones, diabase-chert, sandstones, etc.In keeping with variety of the geological base, soils are various as well.The most frequent soils are rendzina and brownized rendzina, graybrown soil on limestone, black and brownized black soil on serpentines, brown acid soil on crystalline rocks, mineral-pond soil, skeleton-rock soil, etc. (P a v i ć e v i ć et al., 1968).
The examined area is in a zone with the humid temperate-continental and humid alpine types of climate and has average annual precipitation of 700-950 mm.During the year, there are 98 days with persisting snow.Average monthly temperatures range from -4.6 o C to 17.7 o C (the average annual temperature is 7 o C), and relative humidity varies from 71 to 85%.
Southwest Serbia belongs to the Illyrian Province and the Central-European biogeographic region.The potential forest vegetation would include the following communities: Quercion frainetto Horv., 1954;Alno-Quercion roboris Ht., 1938;and Vaccinio-Piceion Br.-Bl., 1939.However, due to diversity of the relief, geological base, and soil, vegetation along the Uvac River is quite varied.The forest vegetation consist of substantial Scotch pine forest remains [assoc.Pinion sylvestris (Achingen 1933);Lakušić, 1972].Austrian pine is very rare and appears either as a single tree or in smaller groups (assoc.Pinetum sylvestris nigrae Pavl., 1951 1955,1962,1964).Through natural succession, the forests of Scotch and Austrian pine were penetrated by elements of deciduous forests, primarily Quercus sessilis Ehrh.and Fagus moesiaca (K.Malý) Czecz.In the gorges, there are degraded remains of ancient oak forests and deciduous shrub vegetation of the forest-steppe zone from the association Prunion spinosae Soó 1940.The part of the gorge from Lupoglava to the very beginning of Lake Zlatar is characterized by the following forest communities: Orno-Ostryetum carpinifoliae Aich., 1933;Alnetum glutinosae-Carpinetum betuli Prov.;Quercetum cerris Vuk., 1966;Quercetum petraeae-cerris Jov., 1979;Querco-carpinetum Rudski, 1949;andFagetum montanum (Rudski, 1949) Jov., 1967.In the limestone areas around Radoinjsko Lake, it is possible to find communities from the association Ostryo-Carpinion orientalis Horv., 1954.Along the lower part of the river very near the river banks (where forests are degraded), there is a specific shrub community with Cotinus coggygria Scop.and Corylus avellana L. as the dominant species.
Valley meadows are found downriver from Ra-doinjsko Lake in small valleys between low hills and the river, where soil is deeper, humidity is higher, and warming is medium.This type of meadow is developed on the boundary part, which is drier and dominated by grasses.On the part closer to the water, there are swamp meadows, where Carex and Juncus species dominate and no clear line exist between the two types.There are also real swamp meadows and ponds along the stream.Throughout most of the year these are either covered with water, or else the level of underground water is very high in that area.It is possible to find bulrush and sedge as well.
The gorge of the Uvac River is a landform of rare beauty that has retained many of its features in spite of the formation of many artificial lakes nearby.In addition to great diversity of the geological and pedological structurea wide variety of vegetation is visible as well, and this give rise to the idea of conducting detailed floristic examinations.One of the goals was to confirm the potential presence of rare, endangered, and endemic species in order to protect this unique gorge as a natural wonder in the given part of Serbia.Most of the area is already under protection as a special reservation encompassing the habitat of the griffon vulture (Gyps fulvus).for identification: J o s i f o v i c (1970)(1971)(1972)(1973)(1974)(1975)(1976)(1977), S a r i c (1986), and T u t i n et al. (1964)(1965)(1966)(1967)(1968)(1969)(1970)(1971)(1972)(1973)(1974)(1975)(1976)(1977)(1978)(1979)(1980).Floristic-geographic data are given according to G a j i ae (1980).
It can be concluded that the Uvac River and its watershed are worth the full attention of botanists.Even partial examinations have already disclosed a remarkable  and very interesting diversity of plants.
Fig. 2. Systematic units and taxa of the flora of Uvac River Gorge.
Fig. 1.Map of Serbia and Montenegro and the examined area.