Checklist of the flora of the vicinity of Balakliya (Kharkiv region, Ukraine): native and alien taxa, distribution of rare plants, new findings

For the first time, information on the flora of the Siverskyi Donets basin in the vicinity of Balakliya town (Kharkiv region of Ukraine) was summarized based on the comprehensive analysis of published data, herbarium material, and own field examinations. Field surveys were conducted during September 2015 and March-July 2016. The surveyed areas were located mainly in the valleys of the Sіverskyi Donets river and some of its tributaries within the former Balakliуa district. The conspectus of flora comprising 933 taxa of vascular plants (including 798 recorded during field surveys) has been prepared. In particular, 739 taxa of native and 194 taxa of alien plants were recorded. The habitats of 14 species from the Red Book of Ukraine were found. The locations of other protected, uncommon and new for the flora of the region plant species were also identified. Several taxa (i.e., some of the calciphytes like Astragalus albicaulis, Linum czernjajevii, Odontarrhena tortuosa subsp. cretacea, Scutellaria supina, and Silene supina) were found out of their previously known ranges. Newly established locations of some other species (e.g., Ephedra distachya, Onosma simplicissima, and Ornithogalum boucheanum) significantly complement previously known chorological data. Finally, information about new findings of such alien taxa actively expanding new areas as Cornus sanguinea subsp. australis, Fraxinus pennsylvanica, Sedum sexangulare, Ulmus pumila, and Vitis vulpina is provided. It has been established that the flora of the Siverskyi Donets basin in the vicinity of Balakliya town is a rich natural center of phytodiversity being under active adventisation. Forest reclamation plantations play a significant role in spreading the alien plants. Railway and the pine terrace of the Siverskyi Donets also serve the migration corridors for many of such alien plants.


Introduction
Balakliya is a town located in the southeastern part of the Kharkiv region of Ukraine, in the subzone of the Northern Steppe. The complex landscape system of the Siverskyi Donets basin leads to the formation of rich and diverse flora and allows its preservation in Plant Introduction • 89/90 O. Shynder, J. Negrash conditions of significant anthropic pressure. Territorially, the vicinity of Balakliya is located between two national phytodiversity centers, Donetsk-Mzhanskyi and Izyumskyi (Dogadina & Bezrodnova, 2011). There are present all main floristic complexes of the Northern Steppe, including pine, petrophytic (cretaceous outcrops), and halophytic (salt meadows).
In the XIX century, this area left out of naturalists' attention. At the beginning of the XX century, Taliev (1904) inspected the cretaceous outcrops west of the village Milova in the river Milova's valley and noted the poverty of the species composition of its vegetation. Later, Kotov (1965) briefly described the forest vegetation of the Izium forestry on the left bank of Sіverskyi Donets. Today, part of this complex combining various types of forests, floodplain meadows, and sandy areas belongs to the Landscape Park Izyumska Luka (Onyshchenko et al., 2016). Lavrenko (1973) inspected the western part of the Andriyivskyi Sukhyi Lyman within the former Balakliya district. Aquatic and coastalwater flora and vegetation of the Siverskyi Donets basin in the vicinity of Balakliya has been studied by several scientists (Chernaya, 1982;Dubyna, 2006;Kazarinova, 2015). There are also some publications about some locations, predominantly of rare species, in this region (Bezrodnova, 2015;Gorelova & Alekhin, 2002;Melnyk & Parubok, 2004;Shynder & Saidakhmedova, 2018;Vinichenko, 2007), including the fundamental work "Flora of the Ukrainian SSR" (Kotov et al., 1936(Kotov et al., -1965.
Please also see the additional list of references in the Appendix.
Despite intensive investigations, the flora of the Siverskyi Donets basin within the Balakliya vicinity remained incompletely studied. Chorological data are crucial for protecting the rare plants and their habitats, particularly because, in the former Balakliya district's territory, there are located five sites of the Emerald Network (2021).

Material and methods
Field surveys were conducted during September 2015 and March-July 2016. The surveyed areas are located mainly in the valleys of the Sіverskyi Donets river and some of its tributaries within the former Balakliуa district. According to the new scheme of administrative-territorial zoning of Ukraine, our research area covered the communities of Balakliya town and the Donets settlement.
Collected specimens (403 species on 579 herbarium sheets) were deposited at the Herbarium of the M.M. Gryshko National Botanical Garden of the NAS of Ukraine (KWHA). The plants' photos from the studied area were also partly uploaded to the iNaturalist (2021) database.
The whole set of discovered taxa was divided into two main fractions -native and alien plants. Alien plants include those that penetrated the research area in the historical epoch (from ancient times to the present day). To clarify the primary distribution ranges and habitats of plants, we used several principal reference works (Prokudin et al., 1977;Protopopova, 1991;Scholz, 1996;Geltman, 2006;Iljinska et al., 2007;Protopopova et al., 2009;Zvyagintseva, 2013;Protopopova & Shevera, 2012, 2019. Many alien plants were first cultivated, and after that, they naturalized and spread spontaneously to the wild (escaped plants). Such escaped plants were included in the checklist only in case of confirmed reproduction by seeds outside of the primary cultivation area.
The nomenclature of taxa conforms to the Plant of the World Online (2021) and Euro+Med PlantBase (2021) databases.
Some locations of rare taxa listed in the Red Book of Ukraine (Didukh, 2009) were already known for the vicinity of Balakliya, so we present them here as confirmed.
It should be noted that the names of forests and forestries to which these forests belong do not coincide. For  Balakliya -the valley of the oxbow Lyakhova, the branch of Siverskyi Donets (49.456931 °,36.821375 °); Balakliya -W, sandy steppe on the pine terrace of Siverskyi Donets (49.463975 °,36.784181 °); Protopopivka -NW, cretaceous outcrops on the slopes of a large gully (49.255167 °, 36.902175 °). Many taxa in the studied area exist on the limit of their natural habitats. At the beginning of the 20th century, Lavrenko (Lavrenko, 1973;Kotov et al., 1936Kotov et al., -1965) discovered many edge locations of boreal plant species that grow in the swamps of the Siverskyi Donets basin and on its sandy terraces in pine forests between Balakliya and Zmiiv. Most calciphytes in the studied area are on the verge of their geographical distribution. Our findings of some of them (e.g., Astragalus albicaulis, Cotinus coggygria, Linum czernjajevii, Pimpinella tragium subsp. titanophila, Scutellaria supina, and Silene supina) expand existing vision about their natural habitats. Among the plants that grow in the steppe habitats along the edge of their geographical distribution in the studied area are Ephedra distachya, Erysimum aureum, Inula salicina subsp. sabuletorum, Onosma simplicissima, and Ornithogalum boucheanum.
Among the actual directions of floristic researches is the fixation and monitoring of alien plants, many of which pose a threat to aboriginal biodiversity. Many alien plants in the new habitat are becoming invasive -they reproduce en masse, interfere with the normal functioning of natural ecosystems, and often suppress and displace native plants (Protopopova et al., 2002(Protopopova et al., , 2009Geltman, 2006;Lambdon et al., 2008;Protopopova & Shevera, 2012).
In Ukraine, Protopopova and Shevera have long studied the questions of phytoinvasion, and recently published the list of highly invasive plants in the flora of Ukraine (Protopopova & Shevera, 2019). According to these authors, the eastern part of the Steppe zone (where Balakliya is located) is classified as a region with a fairly high saturation of species with high invasive potentialover 40 such taxa reported for this region. Zvyagintseva (2013) studied invasive plants directly in the Kharkiv region. She found that the urban flora of Kharkiv includes 312 alien plant taxa, 14 of which have a high invasive potential and are widespread in both artificial and natural phytocoenoses of the urban area.
Below we represent detailed descriptions of the locations of native plants listed in the Red Book of Ukraine (Didukh, 2009) and which are rare or present on the edge of the range of their natural distribution. This list is supported by notes about newly discovered alien plants in the flora of the Balakliya district. The complete list of taxa of the flora of the vicinity of Balakliya, including the citations of taxa authors, is represented in the Appendix.
Although the generalized list of taxa looks large, it is probably still not complete since we have not been able to cover all ecological groups of plants in the vicinity of Balakliya one individual was found near a small roadside plantation in the Siverskyi Donets floodplain (49.426039 º, 36.834686 º) (KWHA).
Gladiolus imbricatus (RBU) -According to literature sources, this is a rather widespread species in the vicinity of Balakliya (Gorelova & Alekhin, 2002). We noted a large population of the species in the floodplain on the leftbank meadow of the Siverskyi Donets, toward the north from the village Bayrak (KWHA). More than 200 generative individuals of the species were recorded on a 100×200 m plot near the Balakliya-Izyum highway (49.426319 °, 36.833014 °). The locus of this population is noted in the east vicinity of Bayrak, on the edge of a deciduous grove, at the top of the slope (49.417950 °, 36.842819 °) (KWHA). Ten generative individuals were growing on the forest's edge. Also, 14 generative and four virginal individuals grew nearby on fallow.
Iris arenaria (RBU, BC) -Western vicinity of Balakliya, sandy steppe, several dozen small clumps of plants (KWHA); south-western vicinity of Balakliya, Kreydyanska Dacha, the quarter Nr 29, and, partly, the western edge of the quarter Nr 30 of the Balakliyske forestry (49.433619 °, 36.818361 °), Landscape Reserve of Local Significance Kreydyanska Dacha (KWHA). In this population, on a total area of about 4 ha, we found near 100 individuals and their groups, mostly with 1-5-flowering shoots. In the most prominent clumps of this population were recorded 69 flowering shoots per 1 m 2 . Besides RBU, this taxon is also included in the list of rare species of the Landscape Park Izyumska Luka (Onyshchenko et al., 2016).
Iris pumila (r.s.) -South-eastern vicinity of Borshchivka, at the top of a large gully, along the edge of the plateau (f.r.).
Liparis loeselii (RBU) -It is included in the list of rare species of the Landscape Park Izyumska Luka (Onyshchenko et al., 2016). Requires confirmation.
Ornithogalum boucheanum (RBU) -Southwestern vicinity of Borshchivka, in a ravine on the northern slope of a large gully (49.471361 °, 36.970133 °) (KWHA). This young population has the form of a stripe up to 30 m long. About 80 generative and over 100 virginal individuals have been recorded here. This species is O. Shynder, J. Negrash occasionally cultivated in Balakliya. Toward the west from the city center along the Lyakhova river banks, cultivated plantations of the species occasionally occur near the dwelling. Besides, planted and self-seeding clumps of the plants occur in the forest park (KWHA). Here, a spontaneous population of introduction origin is establishing.
Stipa borysthenica (RBU) -Between Balakliya and Andriyivka -Borysoglibskyi Bir, several small loci on the lawn in the quarter Nr 46; on felled areas and along the glades in the quarters Nrs 57 and 65 of the Vysokobirske forestry (KWHA).
Stipa capillata (RBU) -The species is quite widespread and is listed for the Balakliya district from the outskirts of Dovgalivka (Bezrodnova, 2015) and other villages. We recorded the following locations: western vicinity of Balakliya -Borysoglibskyi Bir, the quarter Nr 128 of Vysokobirske forestry, a few individuals (KWHA); the eastern part of Balakliya, on the side of the highway, several young clumps of plants (KWHA); southeastern vicinity of Borshchivka -in a large gully, on the slopes, abundantly (KWHA); north-western vicinity of Borshchivka -near the road on the right slope of the valley of the Voloska Balakliyka river (f.r.); between Milova and Glazunivka -on cretaceous outcrops and steppe areas (KWHA); north-western vicinity of Protopopivka -a large gully, on the tops of the slopes, abundantly (KWHA); Protopopivka, the bank of Siverskyi Donets, on steep slopes, in some places abundantly (f.r.).
Stipa pennata (RBU) -North-eastern vicinity of Glazunivka -a slope in the upper reaches of the valley of Milova river (KWHA); south-eastern vicinity of Borshchivkain a large gully (discovered together with N.B. Saidakhmedova), locus 40×15 m above the edge of the abandoned quarry (Fig. 2), several clumps of plants on the edge of pine stands, above the slope (KWHA); north-western vicinity of Protopopivka -on the cretaceous outcrops of a large gully, abundantly (KWHA).
Tulipa sylvestris subsp. australis (RBU) -Balakliya -in the floodplain forest park along the oxbow Lyakhova, many small clones (KWHA); northern vicinity of Bayrakfloodplain grove on the left bank of Siverskyi Donets, near the highway (KWHA); southeastern vicinity of Bayrak, in the forest on the slope, abundantly (f.r.).
Adonis vernalis (RBU) -The species is provided from the vicinity of Milova and Pyatygirske (Melnyk & Parubok, 2004). The phrase " Balakliya district, Kirovo (Herbarium CWP, 1995)" (Melnyk & Parubok, 2004) probably refers to Kvitneve (former name -Kirove village) in the Blyznyukivskyi district of Kharkiv region. We confirmed the occurrence of A. vernalis in the south-western vicinity of Milova -on a small section of the meadow steppe, on the southern slope of the valley of the Milova river (slope 30 ° of north exposure), near the Shebelynskyi chalk quarry (49.433981 °, 36.666033 °) (KWHA). Over 50 generative individuals were found here in the plot of 30 × 30 m. Another locality was found in the north-western part of Protopopivkaon the cretaceous outcrops on the northern slope of a large gully (slope of south-eastern exposure with 5-30 ° inclination) (49.433981 °, 36.666033 °) (KWHA). Up to 500 generative individuals grow on a 200×100 m plot.
Astragalus pallescens -Borshchivkanorth-western vicinity, the northern slope of the valley of the Voloska Balakliyka river, on the roadside (KWHA); Borshchivka -southeastern vicinity, on the slopes of a large gully, abundantly (f.r.).
Checklist of the flora of the vicinity of Balakliya (Kharkiv region, Ukraine) Clematis integrifolia (r.s.) -Milova -southwestern vicinity, the southern slopes of the valley of the Milova river, occasionally (KWHA).
Onosma simplicissima (RBU) -Milovasouth-western vicinity, on the cretaceous outcrops of the southern slope of the valley of the Milova river (KWHA).
Pulsatilla pratensis (RBU) -widespread on the pine terrace of Siverskyi Donets, recorded in many quarters of Balakliya (KWHA) and Vysokobirske (KWHA) forestries. In some quarters, including felled areas, it has a high population density.
Scutellaria supina (RBU) -It is reported for the vicinity of Pyatygirske (Bezrodnova, 2015). We found probably the same locality in the south-western vicinity of Milova on cretaceous outcrops (KWHA).
Thymus × dimorphus -Borshchivkasouth-eastern vicinity, on the slopes of a large gully (KWHA); Borshchivka -northern vicinity, the northern slope of the valley of the Voloska Balakliyka river (KWHA); Protopopivkanorth-western vicinity, cretaceous outcrops of the northern slope of the great gully (KWHA).
Tragopogon podolicus -It is provided for the city of Balakliya and neighboring districts (Klokov, 1965), but in the recent revision it is not indicated for the region (Gorelova & Alekhin, 2002). We recorded the following localities: Balakliya -the northern part, the territory of the military base (KWHA), and near the railway station (f.r.); Balakliya -western vicinity, sandy steppe (f.r.), and along the pine terrace of Siverskyi Donets (f.r.).
Artemisia biennis -Balakliya -near the railway station, in the culture near the estate and nearby, on the ruderal areas, several dozen individuals (KWHA).
Cornus sanguinea subsp. australisthroughout the territory, often in forest plantations, from which it spreads to the adjacent territories, in particular, in the town of Balakliya -along the railway.
Fraxinus pennsylvanica -sporadically in forest plantations, from which it spreads to the adjacent areas.
Phedimus hybridus -Balakliya -southwestern vicinity, Kreydyanska Dacha, the quarter Nr 22 of the Balakliyske forestry, several plants' clumps in the pine forest, on both sides of the trail (KWHA).
Ptelea trifoliata -Bayrak -western vicinity, in forest plantations near Khomyn ravine and on the slope of the valley of Siverskyi Donets (KWHA).
Ribes aureum -It is occasionally cultivated and occurs in forest crops, where it produces self-seedings. The following spontaneous habitats were noted: Balakliya -surrounding, Kreidyanskyi Bir, the quarter Nr 8 of Balakliyske forestry (KWHA); ibid., the quarter Nrs 50 and 51 (f.r.); Bayrak -western vicinity, afforestation on the edge of the slopes of the valley of Siverskyi Donets (f.r.).
Sedum sexangulare -Between Balakliya and Andriyivka -Borysoglibskyi Bir, the quarter Nr 44 of the Vysokobirske forestry, several clumps of plants on a clearing in the pine forest (KWHA); in the same forest, quarter Nr 11, on a sandy road, a small number. The finding of this Central European species in the Balakliya district's flora indicates that this species migrates to the east along the pine terraces of Siverskyi Donets, expanding its secondary range.
Ulmus pumila -Adult 30-50-yearold individuals occur in urban plantations in Balakliya and some plantations in the forestries. Invasive colonies were noted in certain places: Balakliya -center, around the park (KWHA); western vicinity of the Balakliya cement plant -on the edge of Borysoglibskyi Bir, planted trees and in some places selfseeding individuals are abundant (f.r.).
New locations of aboriginal and alien plant species of the Siverskyi Donets basin in the Balakliya region supplement the existing information about the region's flora. The overall floristic richness of the Balakliya region is relatively high, although it is conceding to the well-known regional centers of phytodiversity. All the main floristic complexes of the Northern Steppe (nemoral, boreal, steppe, psammophytic, calcephytic, meadow, and swampy) are combined in the Balakliya natural center of biodiversity. The landscape basis of this center is formed by the valley of Siverskyi Donets with a system of tributaries, which is located between the Lyman group of lakes from the northwest and Izyumska Luka from the east.
Some of the listed species were found within the Landscape Reserve of Local Significance Kreidyanska Dacha (quarters Nrs 18-21, 24-30, 32-38, and 45-67 of the Balakliyske forestry). In particular, large populations of Jurinea cyanoides and Pulsatilla pratensis and the local population of Iris arenaria are located there, which testifies the phytodiversity value of this reserve. During the study, other valuable areas with rare plants deserving protection, particularly the steppe gully in the vicinity of Borshchivka (Shynder & Saidakhmedova, 2018), were also found.
Many alien (mostly escaped) plant species, which are new to the flora of the region and are in the expansiaon process, were recorded. Here, the most invasively active are taxa that are widely used in forest reclamation plantations (i.e., Cornus sanguinea subsp. australis, Fraxinus pensylvanica, Prunus mahaleb, P. serotina, Ptelea trifoliata, Robinia pseudoacacia, and Ulmus pumila). The railway helps distribute the adventive plant species, among which are xenophytes (alien plants that spread spontaneously, e.g., Mirabilis nyctaginea) and escaped plants (primarily those used in the wind-breaking plantations). Many adventitious species were recorded on the pine terraces of Siverskyi Donets, indicating favorable conditions for them.

Conclusions
In general, 933 taxa of vascular plants were recorded in the flora of the Siverskyi Donets basin within the former Balakliya district of the Kharkiv region of Ukraine, including 798 taxa observed directly during the field surveys. Such high taxonomic diversity indicates that the studied area is a large regional center of floristic diversity, formed by all the Northern Steppe's major floristic complexes. Moreover, many new rare aboriginal plant taxa locations were discovered, which testifies the high sozological value of some areas. UA0000073 -Iziumska Luka Regional Landscape Park. https://natura2000.eea.europa.eu/Emerald/SDF. aspx?site=UA0000073&release=3 Checklist of the flora of the vicinity of Balakliya (Kharkiv region, Ukraine) Appendix. Checklist of the flora of the outskirts of Balakliya within the former Balakliya district (Kharkiv region, Ukraine).
Besides the species observed directly on the studied flora territory, over 40 additional species that were found close to the administrative boundary of the former Balakliya district are represented in this checklist. Some of them may be detected within the study area in the future. Such species are listed without numbers. Also, to avoid mistakes in the future, several taxa that are clearly erroneous or were not confirmed in other sources are included in this checklist.

Appendix. Continued.
Checklist of the flora of the vicinity of Balakliya (Kharkiv region, Ukraine)
Checklist of the flora of the vicinity of Balakliya (Kharkiv region, Ukraine)