The vegetation of “Bila Skelya” tract (Yavoriv National Nature Park, Lviv Region)

© 2019 O. T. Kuzyarin et al.; Published by the Ivan Franko National University of Lviv on behalf of Біологічні Cтудії / Studia Biologica. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://www.budapestopenaccessinitiative.org/ and Creative Commons Attribution 4.0 License), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. UDC: 581.526

It was found that the formation of species of "Bila Skelya" tract in the beech forest with rocky sandy outcrops counts 127 species of higher plants, including 121 species of vascular plants and 6 epigene mosses. Syntaxonomic composition (three meadow and forest plant groups), peculiarities of their ecological-coenotic structure and sozological value of the vegetation of the tract were explored.
It was established that plant groups are at the stage of sylvatization and partially recreational succession followed by regressive changes in structure and species composition (depletion of species diversity). The pines overgrowth on the slope is accompanied by changes in the illumination, hydrological and salt regime of the soil (acidification), which will lead to gradual displacement of xerothermophilic and psamophilic herbaceous species and a complete replacement of meadow class groups Trifolio-Geranietea on

INTRODUCTION
Roztochya is a unique physically-geographical region, where two decades ago Yavoriv National Nature Park (YNNP) was created to protect valuable natural complexes whose functions, except of nature conservation, are environmental, educational and recreational investigation. An important task of the park is to study the structure and dynamics of vegetation under the influence of recreation. One of valuable geobotanical complexes of the YNNP is the rocky outcrop at the north-western edge of low humpback mountain range which extends along the left bank of the Vereshchytsya River in the vicinity of Lelehivka village. This outcrop on the slope of south-western exposition up to 5 m in height composed by interlayer layers of the Neogene sandstones and sands, was described as early at the end of the 19th century. In the Geological Atlas of Galicia of A.M. Lomnytskyj (Łomnicki, 1998, p. 92) [13]. Here, on the rock ledges Carpathian beech forests nearby steppe vegetation are growing on the hilly strands. At the foot of the hills, there is a pine forest and in the valley of the Vereshchytsa River there are marshes and marsh complexes on the Black Lakes. The part of the strand with detachment known as "Bila Skelya" tract is an interesting geological, geomorphological and botanical object for studying and exploring the conservation conditions of rare xerothermal settlements in the region.
In the recent years, phytocenologists have been trying to reduce vegetation phytocenotic descriptions that were accumulated for more than a decade to a single classification. This concerns the syntaxonomy of xerothermic vegetation [6,18]. The Ukrainian geobotanists explored the meadow-steppe vegetation of the Forest-steppe [11], northwestern Podillya [7], West Podillya, including nature monuments, the Kasov and Chortov mountains [10], "Step Masyok" tracts with fragments of the Trans nistrian steppe [5], in particular. The vegetation of the crystalline outcrops of the Ukrai nian shield by I.S. Kontar (2000) [9]. The vegetation syntaxonomy analysis of the Roztochya region was performed by M.I. Soroka (2008) [17] and Yavoriv NNP by M.M. Zagulsky et al., 2000) [8,19]. Due to the relevance of phytososological researches and the elucidation of the dynamic tendencies of vegetation, the aim of our work was to study the ecologicalcenotic structure of plant communities of "Bila Skelya" tract.

MATERIALS AND METHODS
The work study was based on the results of floristic and geobotanical searches performed during 2018 and 2019 within " Bila Skelya" tract of YNNP, located on the left bank of the river Vereshchytsya in 47 th quarter of the Maidan Forestry of the Starytskyj military forest management. The "Bila Skelya" tract is elevated, armored by limestone and sandstone section of the sloping hill with sod-slightly podzolic sandy loam in combination with sod-carbonate mid-loam soils (Organization Project…, 2011) [4]. Here is an ecological route "Lelehivka" and Ivan Franko "Ecological Path" that are visited by many pupils and students for educational purposes. Also, there are pounds used for recreation.
According to the "The project of organization…", 2011 [4], two lithologic-stratigraphic complexes are well-distinguished in the Quaternary formations in the geological structure of Yavoriv NNP territory, separated by a stratigraphic and angular incongruity: lower (Upper Cretaceous Mesozoic era) and upper (Paleogene-Neogene (the third period of the Cenozoic era). The Upper Cretaceous deposits form a "base" of modern relief, covered by a powerful surface of Paleogene-Neogene and Quaternary deposits. Paleogene (Eocene) deposits have little capacity and island (fragmentary) distribution in the park and they are recorded mainly in its north-east part. The Neogene deposits lie on the uneven blurred surface of the Upper Cretaceous and Eocene deposits and form almost continuous cover whose, the formation, occurred during the Baden (Tortonian) time.
Typical section of the main stratigraphic elements of the Lower Baden Stratum (Miocene epoch) is Mykolayiv layers formed under the conditions of extensive maritime transgression, outcrops in the neighboring area of our investigations in quarter 33 Yaniv Nature Research Branch of the YNNP [4]. The lower baden has a two-membered structure. Its lower and major part is formed by a relatively heavy (up to 60-80 m) light (white and light gray) sandy deposits composed of quartz, rarely quartz-glauconite sands. Occasionally, there are layers of poorly cemented sandstones, remnants of isolated tree trunks and seashells. The upper part of the section of the Lower Baden formations of the park (2-4 m thick) is characterized by the presence of layers of cemented coarse-grained limestone, which are wholly or partially composed of the remains of the limestone algae. These are Naraev groups of second or middle lithotamni horizon.
The vegetation cover of the studied area is represented mainly by tree stands and is closely related to the nature of the soil. As noted by A.M. Lomnytskyj, there were limestone prevailing, in particular on the top and at watershed surfaces -beech dominates, and on sandy soil, mainly on slopes -pine. The oak occupies an intermediate position, being a part of groups of both beech and pine forests. The appearance of the outcrop and the formation of a xerothermal settlement were probably facilitated by a road laid at the foot of Bila Skelya, since miocene deposits have long been used by local residents for various economic needs, including construction.
Collection of field material was performed by means of conventional methods -itinerary and semi-stationary. Phytocenotic descriptions and their analysis were performed on the basis of ecological-floristic classification (Brown-Blank method) [3]. For identification and comparative evaluation of vegetation units of the tract were used works of the Ukrainian [11,16,17] and foreign [14,18] researchers. Latin names of vascular plants are given by S.L. Mosyakin, M.M. Fedorochuk [15], bryophytes -according to modern taxonomy [2].

RESULTS AND DISCUSSION
Based on the conducted phytocenotic descriptions (Table), the floristic and syntaxonomic content of the vegetation part of "Bila Skelya" tract was analyzed covering transformed xerothermic meadows (groups 1-3) and beech forest (groups 4).
Specific ecotope conditions of the investigated xerothermic meadows, including geological, geomorphological and soil-hydrological, and their marginal location determine their rich floral composition and the coenotic role of individual species. Specific saturation of groups ranges from 53 to 92 species of higher plants (vascular and bryophytes) within three descriptive areas.
The studied group are marked by a relatively complex four-tiered vertical structure (with wood, shrub, grass and mossy tiers). In the rarefied (40-75 %) tree stand Pinus sylvestris is dominated about 15-25 years old and 8-12 (15)  union. For a long time it was mistakenly believed that Festuca pallens was growing on the White Rock. Subsequently, it was proved that the population Festuca psammophila is represented here and its place of growth is easternmost in Europe and needs protection at the national level [1]. In the most illuminated area, this species are represented as a co-dominant, forming a projection coverage of about 15 %.
Based on the analysis of the floristic composition and coenotic structure of the investigated xerothermic bows, we concluded that the formation of these groups occurred in the nineteenth century and is obviously related to the laying of the road and the functioning of the elemental quarry (sandstone mining). At the present stage, these phytocoenoses are intensively overgrown with forest species that threatens their further existence.
Beech forest grouping (association Dentario glandulosae-Fagetum) (see table), located on top of the hump and border with xerothermal bows, belongs to the alliance Fagion sylvaticae, order Fagetalia sylvaticae, class Querco-Fagetea. It accomplies with the Dentario glandulosae-Fagetum Klika 1927 em. W. Mat. 1964 association by the ecological-cenotical structure. Its sozological value is determined primarily by the presence of rare species such as Neottia nidus-avis and Platanthera chlorantha, listed in the Red Book of Ukraine.

CONCLUSIONS
It was found that species diversity of a large part of the "Bila Skelya" tract on the slope of the south-western exposure of the sandy mountain counts 127 species of higher plants, including 121 species of vascular plants and 6 epigene mosses.
Syntaxonomic composition is clarified (one association -Dentario glandulosae-Fagetum and three basal groups: Pinus sylvestris -Anthericum ramosum -Teucrium It has been established that plant grouping is at the stage of sylvatization and partially recreational succession with subsequent regressive changes in structure and species composition (impoverishment of species diversity).
The pines overgrowth on the slope is accompanied by changes in the illumination, hydrological and salt regime of the soil (acidification), which will lead to the gradual displacement of xerothermophilic and psamophilous herbaceous species and the complete replacement of xerothermic meadow groups class Trifolio-Geranietea on Quenco-Fagetea forest coenoses. This process can be stopped only by regulating (limiting) the undergrowth of trees (by carrying out periodic sanitary cabins).
Four species registered in the Red Book and four regionally rare species grow in factions. As many species are found here at the border of the range and are rare for Roztochya.
Thus, to save valuable natural complexes of the "Bila Skelya" tract whose area is 38 hectares (47th quarter of the Maidan Forestry of the Starytskyj military forestry), we recommend its transferring to the Yavoriv NNP for a permanent use.