Floristic features

Vojvodina is a typical agricultural area where all types of natural habitats are endangered by surface reduction, fragmentation and spatial isolation. More than three quarters of the area is overgrown with crops, ie 74.5% is cultivated, and 6.8% are meadows and pastures, which indicates that 82.8% of the area is under agriculture (Adamović, 2008). This indicates that there are fewer natural habitats, as well as a pronounced fragmentation.

Fragmentation of natural habitats has caused the loss of natural habitats, spatial isolation and uneven spatial distribution, which leads to the loss and further endangerment of biodiversity. Natural vegetation has been preserved in the form of smaller or larger isolated oases such as marshes, salt marshes, uncultivated parts of loess terraces, loess plateaus, and every other type of habitat that could not be converted to agricultural land. Steppe, sand and saline soil habitats are the dominant types of natural, primordial vegetation of Vojvodina. Pannonian loess steppe meadows, Pannonian sand steppes, Pannonian land dunes, Pannonian salt steppes and salt marshes were valorized as priority habitats of protection in Serbia (Ordinance on criteria for habitat types, vulnerable, endangered, rare and priority protection habitat types and protection measures for their conservation, “Official Gazette of RS”, 35/2010), as well as in EU countries (Habitats Directive – Directive 92/43 / EEC Annex I), which indicates their endangerment on an international scale.

The area of Okanj is dominated by Pannonian light salt steppes and salt marshes protected as a priority habitat type in the European Union. This area is characterised by a salt lake formed in the paleomeander of the Tisza river. It is surrounded by ponds and salt marshes of different salinity, and the remains of the steppe which are present in the higher parts. Okanj pond, in addition to Slano Kopov and Rusanda pond, is a specific center of halophytic species and ecosystem diversity in the Pannonian plant-geographical region, and is very significant ecosystem in context of the entire continent of Europe.

Flora and vegetation of Okanj pond, as one of the representative areas with salt, muddy and occasionally dried ponds on chloride solonetzes, has so far not been the subject of botanical studies. However, there are some data related to saline soil vegetation and wetland saline vegetation in the area of Vojvodina. Slavnić (1939, 1947, 1948, 1953) studied the halophytic vegetation of marshes in Vojvodina from the phytocenological, plant-geographical and economic point of view. Kujundžić (1979, 1980) researched the saline soil ecosystems of Bačka. Parabućski (1978) gives the syntaxonomic position of the salt marshes of western and southern Bačka on the basis of phytocenological research. Furthermore, there are numerous works by Hungarian authors (Bodrogközy, 1963-1964; Soó 1964-1973) on saline soil vegetation, which are important for the research of halophytic vegetation in Vojvodina.
The data on flora and vegetation presented in the study of protection is the result of field research in the period from 2006 to 2008, whose goal was valorization of natural assets, in order to establish the protection of the area. A complete inventory of flora has not been made, since the emphasis was on phytocoenologically significant species that are plant-geographically important, protected, endangered or of national and international importance for biodiversity conservation.

Plant species important for the conservation of species diversity

There are 28 species and subspecies recorded in the group of nationally and internationally important species. There are 8 taxa in the category of strictly protected at the level of species and subspecies (Cirsium brachycephalum, Plantago schwarzenbergiana, Salsola soda, Scilla autumnalis, Scirpus lacustris subsp. Tabernaemontani, Suaeda maritima subsp. Pannonica) according to the “Rulebook on the proclamation and protection of strictly protected wild species” (“Official Gazette of RS”, No. 5/10). The European Red List of Globally Threatened Animals and Plants, as well as the IUCN Red List of Endangered Plants (International Union for Conservation of Nature, Red List of Threatened Plants), includes plantago schwartzenberg (Plantago schwarzenbergiana). One of the species (Salvinia natans) is listed in Appendix I of the Berne Convention as strictly protected (App. I, strictly protected plant species, 1992 and 1999 rev., Appendix 1/Annexe 1). The IPA list (IPA Criterion A, endangered species) contains 4 taxa (Cirsium brachycephalum, Limonium gmelinii subsp. Hungaricum, Salvinia natans) (Table 3). The distinctiveness of Okanj flora are species that occupy areal borders and therefore have a narrow distribution. These are the types of Pontic-Central Asian groups of floral elements, ie Pannonian, sub-Pannonian, Pontic-Pannonian, subpontic, subpontic-Central Asian, Pontic-eastern-sub-Mediterranean and sub-Balkan floral elements. The presence of Pannonian endemics and subendems in the flora of the Okanj pond is very significant and indicates the phytogeographical affiliation of this part of Tizsa basin to the Pannonian floral province.
Figure 10: Plantago schwarzenberg (Plantago schwarzenbergiana Schur)

Plantago schwartzenberg (Plantago schwarzenbergiana Schur) is a Transylvanian-Pannonian endemic, a species of international importance for the preservation of global biodiversity (Stevanović, Vasić, 1995). This species has a significant ecological role because it represents a specific component of floristic and vegetation diversity of the Transylvanian – Pannonian region (Butorac, 1999). It grows in large numbers along the edge of the Okanj pond, on moist salt marsh together with puccinellia (Pucineliia distans subsp. Limosa) and sea aster (Aster tripolium subsp. Pannonicus). Plantago schwartzenberg is not rare in Banat salt marshes (Vuckovic, 1986; Knezevic, Boza, 1990; Knezevic, 1990, 1994).

Plumbago (Limonium gmelini O. Kuntze (Willd.) subsp. hungaricum (Klokov) Soó) is a Pannonian endemic, a distinct halophytic species that gives a light purple tone to the area during flowering in summer (Fig. 11). It is located on the southern border of its distribution in Bačka and Banat (Budak, et al., 1990).

Pucinellia distans subsp. Limosa is a Pannonian subendemic, a typical halophytic species that grows on wet depressions and low, periodically flooded parts of salt marshes, and builds a distinctive and recognizable zone. It is located on one of the southern borders of its distribution in Banat.

Aster sedifolius L. subsp. canus (Waldst. & Kitt) Merxm. is also a Pannonian subendemic species and is quite a common species in the Okanj area.

Creeping yellow-cress (Roripa sylvestris subsp. Kerneri Menyh.) has a Pannonian subendemic feature. It grows on moist and slightly saline meadows (Fig. 12).

Picture 11: Plumbago (Limonium gmelini O. Kuntze (Willd.) subsp. hungaricum (Klokov) Soó)
Picture 13: Sea aster (Aster tripolium L. subsp. pannonicus (Jacq.) Soó)
Representatives of the Pannonian floral feature in the reserve are: sea aster (Aster tripolium L. subsp. Pannonicus (Jacq.) Soó), which grows along reeds and on moist alkaline soils (Fig. 13). Cirsium brachycephalum Juratzka periodically occurs in wet habitats along the Nađoš, Žugalj and Okanj ponds (Fig. 14), and has been singled out as important for the preservation of global biodiversity (Stevanović, et al., 1995).

Slika 13: Panonski zvezdan (Aster tripolium L. subsp. pannonicus (Jacq.) Soó)

Picture 14: Cirsium brachycephalum Juratzka )
Pontic-South Siberian-Pannonian endemic specie Suaeda maritima (L.) Dumort. subsp. pannonica (Beck) Soó ex P. W. Ball was only found on a few square meters at the northern end of Okanj pond and this is the third confirmed finding of this critically endangered species in Serbia (Boža, 1999). The fact that this rare species shows significant fluctuations in numbers in registered habitats, as well as that the subpopulation near Okanj pond is probably the smallest in Serbia, emphasizes the need for its protection. Trifolium angulatum Waldst. & Kit. as a sub-Mediterranean species, as well as the subatlantic-sub-Mediterranean species Trifolium ornithopodioides L. (recorded in April 2007) grows on wet, sandy and slightly saline meadows and pastures. Ornamental onion (Allium atropurpureum Waldst. & Kit.) grows on the rests of stepe along the railway tracks between the villages Elemir and Melenci. The population size is about 50 individual plants. The species is in danger of extinction (EN) with a tendency to decrease in number within the habitat. It belongs to the sub-Central European floral element (Pictures. 15 and 16).

Picture 16: Ornamental onion (Allium atropurpureum Waldst. & Kit)

Autumn squill (Scilla autumnalis L.) has a Pontic – Central Asian – sub – Mediterranean floral feature and graces the area every autumn with its lilac flowers (Picture. 17).

Figure 17: Autumn squill (Scilla autumnalis L.)

White sticky catchfly (Silene viscosa (L.) Pers.) is a representative of the subpontine – Central Asian floral element. Only a few (7) individual plants were recorded in the Achilleo-Festucetum pseudovinae community around Okanj pond. (Picture 18). From this group of floral element, Potentilla argentea L. also gives the flora a distinct feature.

Figure 18: White sticky catchfly (Silene viscosa (L.) Pers.)