BRYOPHYTE FLORA OF THE UVAC RIVER GORGE ( SOUTHWEST SERBIA )

In the examined area, 165 taxa were found and identified: 139 taxa from the class Bryopsida and 26 taxa from the class Marchantiopsida. Nine species are red-listed in Serbia. Material was collected from 62 localities, which were analyzed for similarity of chorological and ecological features using the Jaccard similarity index. Analysis of floristic elements and phytogeographic distribution showed that the greatest number of taxa are temperate elements with Holarctic distribution. Results of ecological analysis showed that in regard to the substratum aspect, terricolous, basophilous, and indifferent species were dominant. In relation to the ecological parameter humidity, most species were mesophilous. The majority of identified bryophytes were sciophilous taxa.


MATERIAL AND METHODS
Bryological investigation along the Uvac River were carried out in the period from May 1998 to July 2000.Material was collected from 62 localities, from the source to the delta (Map 1).The collection is deposited in the herbarium of the Department of Plant Morphology and Systematics, Institute of Botany, and Jevremovac Botanical Garden, Faculty of Biology, Belgrade.
The relevant European literature was used for determination.The nomenclature is in accordance with Corley et al. (1981); G r o l l e (1983); C o r l e y and Crundwell (1991), and G r o l l e and Long (2000).Floral elements and distribution were determined in accordance with D u e l l (1983) and D u e l l et al. (1999) and ecological parameters in accordance with Boros(1964).

Fissidens adianthoides
The group of liverworts was represented by 26 taxa from 13 families and 19 genera.Half of the liverworts recorded were from the families Geocalycaceae, Metzgeriaceae, Lophoziaceae, and Scapaniaceae (Fig. 2).
The range of diversity varied from eight taxa in the delta of the Dobroselica River (locality 35) up to 53 taxa in the canyon downstream from the Radoinjska sluice (locality 28).
In all prior floristic examinations conducted in Southwest Serbia, 134 bryophyte taxa were recorded.A large number of taxa (70 genuine mosses and 12 liverworts) are here recorded for the first time in this region so far.
The Jaccard index (J a c c a r d, 1928) was used to analyze bryological similarity between localities was applied.The degree of similarity ranged from 0 to 0.60 (Fig. 3).The greatest index of similarity was recorded between localities 15 and 17, in the canyon at the very beginning of the Zlatarsko Lake.In regard to habitat, these two localities appear very different.However, because of the short distance between them, not a great floristic separation has occurred.This assumption is confirmed by the example of locality 16, which also has a high index of similarity with locality 15.
A high degree of similarity (over 45%) was recorded between most localities.Many of these localities are very close to each other, with similar vegetation and the same geological substratum.
We compared the bryophyte flora along the Uvac River with those of some other rivers which have been examined.Results from the Irigua River in Spain (Martinez and A b a i g a r, 1992) and Red River in the USA (S t u d l a r and S n i d e r, 1989) were used for comparison.On the Irigua River 123 taxa were identified: 80 real mosses and 43 liverworts.The number of species in common with the flora of the Uvac River is 46 and the similarity index is 0.19.On the Red River in the USA, 264 species and infraspecific taxa were recorded.There were 179 real mosses and 85 liverworts.The index of similarity with the bryophyte flora of the Uvac is 0.13.

Chorological analysis
Analysis of floristic elements in accordance with Duell et al. (1999) showed that the greatest number of taxa are temperate elements (40.61%), while the next most numerous group is made up of boreal floral elements (34.0%).These groups are the most numerous among both real mosses and liverworts (Fig. 4).Considering the geographical position of the examined area, between Central Europe and the Mediterranean, more representatives of the sub-Mediterranean bryoflora might be expected.However, if we take into account climatic factors, the hydrological situation, and the geological substratum of the examined area, the current situation is much clearer.
Analysis of phytogeographic distribution (in accordance with D u e l l et al., 1999) showed a dominance of taxa with Holarctic distribution (Fig. 5) for both real mosses and liverworts.

Analysis of ecological parameters
For ecological analysis of the taxa recorded, the following characteristics were investigated: humidity, substrate type, substrate pH, and light.These characteristics were selected in accordance with B o r o s (1964).
Among bryophytes recorded along the Uvac River, mesophilous species dominated (Fig. 6).This applies to both real mosses and liverworts.Almost half of all recorded species of Bryopsida were mesophilous ones.
Though the soil cover near the Uvac River is relatively poor, particularly in the lower part of the river, species that prefer soil as a substrate were most numerous (40.6%).Taxa that prefer rocky habitats made up 38.2% (Fig. 7).The genuine mosses occured mostly on soil, while most of the liverworts were recorded on rocks.Taxa that prefer bark or are indifferent towards habitat were the least numerous.
In regard to substratum pH, basophilous species were dominant (38.8%), but there were also a number of taxa which are pH-indifferent (Fig. 8).Among real mosses, most of the taxa were ones that are basophilous or indifferent.Quite the opposite situation was observed among the liverworts, where acidophilous species were predominant.This situation was to be expected: basic substrata, mostly limestones, are drier.The liverworts prefer a more humid habitat, as can be seen from the humidity analysis (Fig. 6).
It is evident from Fig. 9 that the majority of recorded bryophytes were sciophilous species (48.5%).Among liverworts, with the exception of Scapania aspera, sciophilous species were absolutely dominant.This situation was to be expected for liverworts because most of their taxa prefer a mesophytic habitat.
Examined area, with localities 1-62 and its location within Serbia (insert).

Fig. 2 .
Fig. 1.Number of taxa from families of the class Bryopsida.