Acta Botanica 2-2016 - za web.indd ACTA BOT. CROAT. 75 (2), 2016 157 Acta Bot. Croat. 75 (2), 157–163, 2016 CODEN: ABCRA 25 DOI: 10.1515/botcro-2016-0029 ISSN 0365-0588 eISSN 1847-8476 Early spring fl ora of the Sub-Pannonic steppic grassland (NATURA 2000 site) in Bilje, northeast Croatia Tanja Žuna Pfeiffer1, Dubravka Špoljarić Maronić1*, Vanda Zahirović1, Filip Stević1, Milorad Zjalić1, Katarina Kajan1, Siniša Ozimec2, Melita Mihaljević1 1 Josip Juraj Strossmayer University of Osijek, Department of Biology, Cara Hadrijana 8/A, HR-31 000 Osijek, Croatia 2 Josip Juraj Strossmayer University of Osijek, Faculty of Agriculture in Osijek, Kralja Petra Svačića 1d, HR-31 000 Osijek, Croatia Abstract – The diversity of early spring vascular fl ora was studied in the Sub-Pannonic steppic grassland in the village of Bilje, north eastern Croatia. In all, 109 plant taxa within 35 families were found. The highest number of taxa belongs to the families Poaceae, Fabaceae, Asteraceae, Caryophyllaceae, Lamiaceae and Ro- saceae. Specifi c habitat conditions, characterized by moderately wet and moderately acidic soil with interme- diate fertility and the effects of the continental climate favour the development of different plant life forms. Out of the total recorded plant taxa, hemicryptophytes make up 59.6%, followed by therophytes (22.0%) and geophytes (13.8%). Chorological analysis shows that the most numerous are plants of Eurasian (33.9%), Pontic-Central-Asian (21.1%) and Central European (21.1%) fl oral elements. According to their status in the Red List, three critically endangered (CR), one vulnerable (VU) and three nearly threatened (NT) plant spe- cies were found. Altogether, the steppe-like grassland in Bilje is a unique habitat rich in valuable plants of the Croatian fl ora, including the critically endangered Doronicum hungaricum, therefore it is of great importance to preserve it. Important management tools include mowing and controlling the spreading of cultivated and invasive plant species. Key words: chorological types, fl ora, life-forms, NATURA 2000, Pannonian Region, steppe-like grassland * Corresponding author, e-mail: dspoljaric@biologija.unios.hr Introduction Grasslands, herbaceous communities mostly dominated by grasses (Poaceae) or other graminoids, like Cyperaceae and Juncaceae (Janišová et al. 2011), are among the largest ecosystems in the world. In Europe there are various grass- land types, ranging from humid grasslands in the north and north-west parts of the continent, through steppic and mesic grasslands to the near-desert types that occur in south-east Spain (Owen 2008). Dry grasslands cover much smaller European areas than mesic and wet grasslands and most of them are semi-natural habitats, resulting from centuries of traditional land use, such as grazing, mowing, temporary abandonment of arable fi elds, and/or other disturbance events (Dengler et al. 2014). Dry grasslands involve a vari- ety of grassland biotopes (Rodwell et al. 2002) that are usu- ally present on relatively dry and nutrient-poor soils. Some of the most important dry grassland habitats are Sub-Pan- nonic steppic grasslands of the alliance Festucion valesi- acae (Klika 1931) developed on rocky substrate and clay- sandy sedimentation layers enriched with gravels. Through the centuries, many of Sub-Pannonic steppic grasslands have been destroyed by afforestation and ploughing, or by land abandonment which led to their degradation (Ruprecht et al. 2009). Steppe-like grasslands are dominated by Fes- tuca valesiaca Schleich. ex Gaudin, Carex humilis Leyss., Chrysopogon gryllus (L.) Trin., Stipa species, but they are also important habitats for many rare and endangered plant species (Cremene et al. 2005, Buček et al. 2006, Jones et al. 2010). Therefore, these grasslands are considered biodiver- sity hotspots and included as an EU priority habitat type in the NATURA 2000 network, designated under code 6240*. The Republic of Croatia differs from most European countries with respect to its huge variety of habitats and great diversity of fl ora. Grasslands cover approximately 17.6% of the Croatian terrestrial area (Anonymous 2006). Sub-Pannonic steppic grasslands are very rare and only few occur in the continental part of Croatia. This study focused on the grassland in the village of Bilje situated in northeast ŽUNA PFEIFFER T., ŠPOLJARIĆ MARONIĆ D., ZAHIROVIĆ V., STEVIĆ F., ZJALIĆ M., ET AL. 158 ACTA BOT. CROAT. 75 (2), 2016 Croatia. The most signifi cant contribution to the fl oristic knowledge of the area was given by Zahirović (2000), while there have been no recent scientifi c publications on survey- ing the steppe-like grassland fl ora of Bilje. The aim of the current investigation was to investigate the diversity of spring steppe-like grassland fl ora with special reference to rare and endangered plant species. Materials and methods The study was carried out at the grassland surface at the local cemetery in the village of Bilje (45°36’N, 18°45’E), situated 5 km northeast of Osijek (Croatia, Baranja region, Fig. 1). The area is infl uenced by a continental climate. Ac- cording to data from Osijek meteorological station (1981– 2010), mean air temperature is 11.3 °C with an annual pre- cipitation of 684 mm. Geomorphologically, the study area mostly belongs to the lowland area built of Quaternary sed- iments formed during the Pleistocene and Holocene (Banak et al. 2012). The Holocene sediments are mostly fl uvial sands and sandy clay (Regional plan of the Municipality of Bilje 2005). Steppe-like grassland covers 0.63 ha and it is among the last remnants of dry steppe grasslands of the alli- ance Festucion valesiacae in Croatia. Thus, it is included in the national ecological network of Croatia (designated with code HR2000728) which is a part of the EU NATURA 2000 network. In 2001, the area was protected as a natural monument. The research on the grassland fl ora was conducted weekly during eight fi eld surveys, carried out from the be- ginning of April to the end of May 2015. Plant taxa were identifi ed according to Javorka and Csapody (1975), Knežević and Volenik (1981) and Domac (1989) and ar- ranged alphabetically and systematically. The nomenclature and interpretation of plant life forms (Therophyta – T, Chamaephyta – Ch, Hemicryptophyta – H, Phanerophyta – P, Nano-phanerophyta – N, Geophyta – G) were adjusted according to the Croatian Flora Checklist (Nikolić 2016). Phytogeographical analysis was interpreted according to Josifović (1970–1977), Zahirović (2000), and Ranđelović et al. (2007). Geoelements were described with the follow- ing numbers: 1 – Pontic – Central – Asian, 2 – Central European , 3 – sub-Atlantic, 4 – sub-Mediterranean, 5 – Eurasian, 6 – sub-Boreal, 7 – Adventive plants and 8 – Cos- mopolites. The species were categorized by threat levels according to Nikolić and Topić (2005) and Nikolić (2016), and invasive plant species according to Nikolić et al. (2014). The diversity of environmental grassland parame- ters was determined according to Ellenberg et al. (1994) and adjusted according to the Croatian Flora Checklist (Nikolić 2015). Ellenberg indicator values (EIV) included the following indicators described by numerical scales ranging from 1–9: light (L), temperature (T), salinity (S), moisture (M), soil reaction (SR), and nitrogen (N). Descrip- tive statistical analysis of environmental parameters was carried out using STATISTICA software package (StatSoft. Inc., ver. 12). Results A total of 109 vascular plant taxa (92 species and 17 subspecies) from 35 families were identifi ed during the study period (Tab. 1). Poaceae was the largest taxonomic group (represented by 12 taxa), followed by Fabaceae (10 taxa), Asteraceae (8 taxa) and Caryophyllaceae (8 taxa). Lamiaceae and Rosaceae were present with six taxa, each. Fig. 1. Study area: Sub-Pannonic grassland in Bilje (northeast Croatia). Tab. 1. List of vascular plant taxa occurring in steppe-like grass- land in Bilje in spring of 2015. Life form: H – Hemicryptophyta, T – Therophyta, Ch – Chamaephyta, P – Phanerophyta, N – Nano- phanerophyta, G – Geophyta; Chorological type: 1 – Pontic – Central – Asian, 2 – Central European, 3 – sub-Atlantic, 4 – sub- Mediterranean, 5 – Eurasian, 6 – sub-Boreal, 7 – Adventive plants and 8 – Cosmopolites; Threat levels: CR – critically endangered, VU – vulnerable, NT – nearly threatened; Asterisk (*) denotes in- vasive species. List of taxa Life form Choro- logical types Threat levels SPERMATOPHYTA MAGNOLIOPHYTINA MAGNOLIATAE Apiaceae Anthriscus sylvestris (L.) Hoffm. H 5 Peucedanum oreoselinum (L.) Moench H 1 Aristolochiaceae Aristolochia clematitis L. H 4 Asteraceae Achillea millefolium L. H 5 Ambrosia artemisiifolia L. * T 7 Artemisia vulgaris L. H 8 Doronicum hungaricum Rchb. f. G 1 CR Erigeron annuus (L.) Pers.* H 7 Inula hirta L. H 1 Taraxacum offi cinale Weber H 5 Bellis perenis L. H 2 SPRING FLORA OF THE STEPPIC GRASSLAND IN BILJE ACTA BOT. CROAT. 75 (2), 2016 159 List of taxa Life form Choro- logical types Threat levels Boraginaceae Anchusa offi cinalis L. H 2 Myosotis discolor Pers. subsp. discolor T 2 Myosotis ramosissima Rochel T 8 Brassicaceae Arabis glabra (L.) Bernhardt H 8 Arabidopsis thaliana (L.) Heynh. T 5 Capsella bursa-pastoris (L.) Medik. H 8 Erophila verna (L.) Chevall. subsp. verna T 8 Calepina irregularis (Asso) Thell. T 4 Campanulaceae Campanula patula L. H 2 Campanula rapunculus L. H 5 Caryophyllaceae Cerastium semidecandrum L. H 2 Dianthus carthusianorum L. H 4 Holosteum umbellatum L. T 5 Lychnis viscaria L. subsp. viscaria H 1 Moenchia mantica (L.) Bartl. subsp. mantica T 1 Saponaria offi cinalis L. H 5 Silene latifolia Poir. subsp. alba (Mill.) Greuter & Bourdet H 5 Stellaria media (L.) Vill. T 8 Cistaceae Helianthemum nummularium (L.) Mill. subsp. nummularium Ch 2 Cichoriaceae Hieracium pilosella L. subsp. pilosella H 2 Hypochoeris maculata L. H 5 Tragopogon pratensis L. subsp. orientalis (L.) Čelak. H 5 Clusiaceae Hypericum perforatum L. H 5 Crassulaceae Sedum telephium L. subsp. maximum (L.) Krock. H 5 Euphorbiaceae Euphorbia cyparissias L. H 5 Fabaceae Lotus corniculatus L. H 2 Medicago minima (L.) Bartal. T 1 Medicago sativa L. subsp. sativa H 7 Trifolium alpestre L. H 1 Trifolium repens L. H 5 Trifolium montanum L. H 1 Vicia cracca L. H 5 Vicia grandifl ora Scop. T 1 Vicia lathyroides L. T 2 Vicia villosa Roth subsp. villosa T 1 List of taxa Life form Choro- logical types Threat levels Fagaceae Quercus robur L. P 2 Geraniaceae Erodium cicutarium (L.) Ľ Hér. H 5 Geranium sanguineum L. H 1 Geranium dissectum L. T 8 Lamiaceae Ajuga genevensis L. H 5 Lamium purpureum L. T 2 Mentha aquatica L. H 5 Salvia pratensis L. H 2 Thymus pulegioides L. Ch 2 Glechoma hederacea L. H 5 Oleaceae Syringa vulgaris L. N 7 Papaveraceae Papaver dubium L. T 8 Papaver rhoeas L. T 5 Plantaginaceae Plantago lanceolata L. H 5 Plantago media L. H 5 Polygalaceae Polygala comosa Schkuhr H 5 Polygonaceae Rumex acetosa L. subsp. acetosa H 5 Rumex acetosella L. G 8 Ranunculaceae Pulsatilla pratensis (L.) Miller subsp. nigricans (Störck) Zamels H 1 CR Ranunculus polyanthemos L. H 1 Rosaceae Filipendula vulgaris Moench H 6 Potentilla argentea L. H 1 Potentilla cinerea Chaix ex Vill. H 1 Potentilla heptaphylla L. H 2 Prunus tenella Batsch N 1 CR Geum urbanum L. H 5 Saxifragaceae Saxifraga bulbifera L. H 4 Scrophulariaceae Verbascum phoeniceum L. H 1 Veronica austriaca L. subsp. austriaca H 1 Veronica chamaedrys L. H 2 Veronica hederifolia L. T 2 Veronica persica Poir.* T 8 Valerianaceae Valerianella locusta (L.) Laterrade T 4 Violaceae Viola arvensis Murray T 5 Tab 1. – continued ŽUNA PFEIFFER T., ŠPOLJARIĆ MARONIĆ D., ZAHIROVIĆ V., STEVIĆ F., ZJALIĆ M., ET AL. 160 ACTA BOT. CROAT. 75 (2), 2016 Regarding the distribution of plant life forms (Fig. 2A), hemicryptophytes were dominant (59.6%), followed by therophytes (22.0%) and geophytes (13.8%). According to phytogeographical analysis (Fig. 2B) Eurasian (33.9%), Pontic-Central-Asian (21.1%), and Central-European (21.1%) fl oral elements predominated. Cosmopolites were repre- sented with 13 (11.9%) taxa. Ecological indicatory values (Fig. 3) were defi ned for more than 90% of the plant taxa. The greatest number of plant taxa preferred half-light conditions (38 taxa, EIV L = 7) and relatively warm habitats (32 taxa, EIV T = 6) charac- terized by moderately wet (33 taxa, EIV M = 5) and moder- ately acid soils (41 taxa, EIV SR = 6) with intermediate fer- tility (24 taxa, EIV N = 5). Almost none of the identifi ed taxa (93%) tolerate salty soils (EIV S = 0). According to threat status given in the Red Book of Vascular Flora of Croatia, Doronicum hungaricum Rchb.f., Pulsatilla pratensis (L.) Miller subsp. nigricans (Störck) Zamels and Prunus tenella Batsch are critically endangered (CR), Polygonatum latifolium (Jacq.) Desf., is vulnerable (VU) and Carex praecox Schreber, Iris variegata L. and Orchis morio L. are nearly threatened (NT). In the early List of taxa Life form Choro- logical types Threat levels Viola tricolor L. T 5 Viola odorata L. H 2 LILIATAE Amaryllidaceae Allium sphaerocephalon L. subsp. sphaerocephalon G 1 Allium vineale L. G 2 Narcissus poeticus L. G 7 Narcissus pseudonarcissus L. subsp. pseudonarcissus G 3 Asparagaceae Muscari botryoides (L.) Mill. G 1 Muscari comosum (L.) Mill. G 4 Ornithogalum umbellatum L. G 2 Polygonatum latifolium (Jacq.) Desf. G 1 VU Cyperaceae Carex caryophyllea Latourr. H 5 Carex praecox Schreb. H 5 NT Iridaceae Iris variegata L. G 1 NT Iris sp. G 5 Juncaceae Luzula campestris (L.) DC. H 8 Liliaceae Gagea pratensis (Pers.) Dumort. G 5 Orchidaceae Orchis morio L. G 2 NT Poaceae Anthoxanthum odoratum L. H 5 Apera spica-venti (L.) P. Beauv. T 5 Arrhenatherum elatius (L.) P. Beauv. ex J. Presl & C. Presl H 2 Briza media L. H 5 Bromus inermis Leyss. H 5 Chrysopogon gryllus (L.) Trin. H 1 Dactylis glomerata L. H 5 Festuca rupicola Heuff. subsp. rupicola H 2 Hordeum murinum L. T 8 Koeleria pyramidata (Lam.) P. Beauv. H 2 Poa bulbosa L. H 5 Poa pratensis L. G 8 Tab 1. – continued Fig. 2. Life form (A) and chorological spectrum (B) of steppe-like grassland fl ora occurring in Bilje in spring 2015. Fig. 3. Box and whiskers plot for environmental variables. Ellen- berg indicator values (EIV): L – light, T – temperature, S – salini- ty, M – moisture, SR – soil reaction, N – nitrogen. SPRING FLORA OF THE STEPPIC GRASSLAND IN BILJE ACTA BOT. CROAT. 75 (2), 2016 161 spring fl ora, three invasive species (Ambrosia artemisifolia L., Erigeron annuus (L.) Pers. and Veronica persica Poir) were found. Discussion Northeast Croatia belongs to the Pannonian region. In the period following the last ice age, forest steppes i.e. mo- saic of grasslands and woodlands were parts of the original Pannonian landscape and covered these areas for a long time (Illyés et al. 2007). For centuries, the Pannonian region was heavily infl uenced by humans and consequently, much of the area was converted to productive agricultural land. Today, in the Pannonian Region, dry grasslands occur only as small fragments, mainly on sites not suitable for inten- sive cultivation and agricultural production (Sundseth 2009). The steppe-like grassland in Bilje remained preserved due to the specifi c location in the grounds of the local cemetery. The plant community indicates prevailing environmen- tal conditions in certain habitats (Schaffers and Sýkora 2000). According to Ellenberg indicator values the steppe- like grassland in Bilje is a well-illuminated, relatively warm habitat characterized by fresh soil of average moisture, moderately acid and moderately rich in nitrogen. The alli- ance Festucion valesiacae was also found in warmer, drier, and less nutrient rich habitats in Romania (Dengler et al. 2012), Serbia (Aćić et al. 2015) as well as in the Carpathi- ans and the Pannonian Basin (Dúbravková et al. 2010). Dry grasslands are usually characterized by high spe- cies richness (Dengler and Boch 2008, Purger and Csiky 2008, Zima and Štefanić 2009, Vassilev et al. 2011, Vitasović Kosić and Britvec 2014, Pirini et al. 2014). In comparison of the number of taxa with that of the steppe- like grassland fl ora of the NATURA 2000 site near Bapska, Eastern Croatia (79 taxa, Šegota et al. 2015), we can con- clude that plant species richness of the investigated grass- land in Bilje is relatively high, probably due to the anthro- pogenic infl uence. Human impact may change habitats, leading to the increase in the number of plant taxa (Alegro et al. 2006). The appearance of some species such as Viola odorata, Syringa vulgaris and Iris sp., which were also cul- tivated on the surrounding graves, suggests that anthropo- genic activities mediated their spreading along the grass- land area. However, the early spring fl ora which accounts for more than 80% of the total grassland plant taxa found by the previous fl oristic investigation in Bilje (Zahirović 2000) indicates a well-conserved habitat. A specifi c charac- teristic of its fl ora is the prevalence of Eurasian, Pontic- Central-Asian, and Central-European fl oral elements with a mosaic complex of different steppic species which also were found in steppe-like grasslands in Bulgaria (Vasillev and Apostolova 2013) and Serbia (Ranđelović et al. 2007). The family Poaceae is represented with genera like Festu- ca, Chrysopogon, Poa and Koeleria, together with species from the Fabaceae, Asteraceae and Caryophyllaceae fami- lies, which add certain specifi city to the grassland fl ora in Bilje. These plant families usually characterize steppe fl ora around the world (Türe and Böcük 2007, Matevski et al. 2008). Hemicryptophytes made up the large majority of the re- corded species. This life form is well represented in the Eu- ropean fl ora (Ellenberg 1988) and usually characterizes grassland communities (Šugar et al. 2005). Furthermore, the high number of therophytes indicates the dryness of this region, the modifi cation of the climate (Rauš and Šegulja 1983, Tomašević 2006) and considerable anthropogenic in- fl uence (Mitić et al. 2007). Some of the recorded plant species are listed in the Red Book of Vascular Plants of Croatia (Nikolić and Topić 2005). The critically endangered Pulsatilla pratensis subsp. nigricans grows at several locations in Croatia (Vrbek 2001, Vitasović Kosić et al. 2009, Nikolić 2016), while the steppe-like grassland in Bilje is one of the two reported habitats for Doronicum hungaricum in the country (Nikolić 2016). In northeast Croatia, Prunus tenella is reported as a very rare species (Krčmar and Ozimec 2004, Purger and Csiky 2008). It grows at the edge of the steppe-like grass- land in Bilje. Besides in Croatia, the endangered species Doronicum hungaricum and Prunus tenella, as well as the nearly threatened Iris variegata and Orchis morio, are also included in the national Red Lists of Vascular Flora of some other European countries (Jackowiak et al. 2007, Grulich 2012, Turis et al. 2014). The steppe-like grassland was also marked by the presence of some woody (e.g. Quercus, Sy- ringa) and invasive (Ambrosia artemisiifolia, Erigeron an- nuus, Veronica persica) species. Their occurrence could be an important threat for grassland fl ora. Generally, trees and shrubs encroach on the sites and develop layers of high cover leading to a rapid decrease in species richness (Dú- bravková and Hajnalová 2012). Invasive species, due to the biological characteristics (Lonsdale 1999), may outcompete native species for resources (Brewer and Cralle 2003), sup- press their growth (Jordan et al. 2008), and have a negative infl uence on species diversity (Dogra et al. 2010). Together with habitat loss, the abandonment of the tra- ditional ways of land management and uncontrolled dig- ging of plants have been generally recognized as the most important threats to plant diversity (Young et al. 2005, Nikolić 2016). In the investigated steppe-like grassland, plant diversity depends on the specifi c types of manage- ment. Mowing is an especially important management tool to control the spread of woody plant species. Considering the uncommon position of this steppe-like grassland within the local cemetery where the opening of new burial places is already limited, controlling the spread of cultivated and invasive plant species should be important steps toward long-term persistence of diverse steppe fl ora. Since the plant diversity, characterized by rare and endangered plant species, represents an important and irreplaceable natural resource in these steppe-like grassland, conservation of this habitat is therefore of great importance. Acknowledgements This study was supported by the Environmental Protec- tion and Energy Effi ciency Fund and the Public Institution for the Management of Protected Natural Areas in Osijek- Baranja County. We would like to thank Željko Zahirović, ŽUNA PFEIFFER T., ŠPOLJARIĆ MARONIĆ D., ZAHIROVIĆ V., STEVIĆ F., ZJALIĆ M., ET AL. 162 ACTA BOT. CROAT. 75 (2), 2016 MSc, for his valuable suggestions and support. We also wish to thank the Handling Editor and anonymous review- ers for their constructive comments and helpful suggestions which substantially improved this manuscript. References Aćić, S., Šilc, U., Petrović, M., Tomović, G., Dajić Stevanović, Z., 2015: Classifi cation, ecology and biodiversity of Central Bal- kan dry grasslands. Tuexenia 35, 329–353. 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