Dendroflora of the Nataliivskyi Park (Kharkiv region, Ukraine): taxonomic diversity and monitoring of plantations

To develop measures for the restoration of historic plantations and landscapes of the Nataliivskyi Park (Kharkiv region, Ukraine), the investigations of taxonomic composition and distribution of woody plant taxa, as well as structure of different landscape areas, were carried out in 2018–2019. The recent studies were realized according to the same protocol applied in 1997 by Y. Klymenko, and taking into account previously published data.In 1939, the dendroflora of the Nataliivskyi Park comprised about 100 taxa. Later, the number of taxa significantly decreased, and in 1950 the park’s dendroflora comprised only about 40 taxa. In 1997 there were 74 taxa reported. Since 1997, the taxonomic composition of the park’s dendroflora has been enriched by ten taxa and is currently represented by 84 taxa. Simultaneously, the number of valuable plants in the plantations decreased (only one or two plants represent some such taxa). Due to a bark beetle attack on drought-weakened trees of Picea abies and P. pungens, most of them withered. The area of allotments with Pinus sylvestris and Quercus robur remained almost the same, which indicates their stability. The area of allotments with the domination of such naturalized introducers as Acer negundo and Robinia pseudoacacia and the area of allotments with the domination of neither taxa have increased. In the landscapes, the redistribution of the types of areas appeared. The forest type of landscape became predominant, while the meadow type of landscape has almost disappeared.Hence, to restore historical plantings and landscapes, it is necessary to re-cultivate taxa represented here during the park’s heyday and remove invasive tree species. Although cuttings in protected areas are currently prohibited, our investigations showed that they might help preserve such valuable territories as Nataliivskyi Park.


Introduction
The monitoring of conditions of botanical gardens and parks has great importance for their preservation and restoration. Every activity conducted in a park should follow conclusions and recommendations of monitoring reports. Monitoring also allows revealing tendencies that can be predicted for other similar areas. Methodological issues of conservation and restoration of old parks are discussed by many scientists (Bondar et al., 1974;Agaltsova, 1980;Ilinskaya, 1984;Uspenskaya et al., 1991;Sikora, 2016).
The Nataliivskyi Park was founded in 1884 by Ivan Kharytonenko in Volodymyrivka village of Krasnokutsk district of Kharkiv region, Ukraine. Only in certain places of the primary park area, old trees of Quercus robur L. grew, while most of the territory consisted of bare sands. On the sands, Pinus sylvestris L. plants were planted. As a result, the pine and oak forests are attached to the contemporary park area. Later, lawns and flowerbeds were created near the buildings, and exotic plants were planted closer to the river Merchyk (Klymenko & Kuznetsov, 2015). Hence, the elevation in the recent park area varies from 113 to 154 m a.s.l.
The Nataliivskyi Park was examined by one of us in 1997 (Y. Klymenko, the results were not published), and in 2018-2019 it was examined for the second time by both of us using the same protocols. During this time, there was a lack of financial support for this park. Any (including sanitary) felling was prohibited. Moreover, tangible climate changes, including extensive droughts, occurred. Therefore, our recent examination was important and should elucidate the influence of mentioned factors on the taxonomic composition and vegetation structure of the Nataliivskyi Park.

Material and methods
The total area of Nataliivskyi Park covers 48 ha. However, Mayak & Cherkasova (1989), as well as the current landowner (Regional Tuberculosis Sanatorium "Volodymyrskyi"), ascribe only 37.8 ha to the park territory. Our surveys were realized by the route method in 2018-2019, taking into account the last indicated area.
The park territory has been subdivided into sections according to prevailing taxa and vegetation types. Sections representing the species with less than five plants per each (i.e., sections with no prevailing species) were marked with a special sign. Park landscapes were classified according to Rubtsov (1956Rubtsov ( , 1979, who distinguished six their main types: sylvatic, park, meadow, garden, regular, and alpine. Basing on this classification and topographical plan of the park received from the Mapgeofund of Ukraine, the schematic plan was drawn out, and the area of each landscape type was calculated in ArcView GIS 3.2a environment. The plant names are provided according to Plants of the World Online (2021).

Results and discussion
The schematic plan of plantings of the Nataliivskyi Park in 1997 is represented in Fig. 1, and the respective plan for 2019 -in Fig. 2. In 22 years, some buildings, including historical ones, were destroyed. Some routes have disappeared, and some new were created. In general, the area under paths increased, while the area covered by buildings decreased. The area under plantings also slightly decreased (from 34.65 ha in 1997 to 34.55 ha in 2019).
In 1939, in the Nataliivskyi Park, trees and shrubs of around 100 taxa grew (Lypa et al., 1952). Later, the number of taxa significantly decreased, and in 1950 the park's dendroflora comprised only about 40 taxa (Lypa, 1960). Kurdyuk (1966), whose research is precious since it reflects the initial structure of the park, reported the big (over 60 trees) groves  There grew not many shrubs (represented mainly by Sambucus racemosa L., Philadelphus coronarius L., P. inodorus L., Syringa vulgaris L.), and all of them were distributed sporadically (Kurdyuk, 1966).
Later, the list of 22 taxa introduced in the park was published (Kokhno et al., 1975). The report of the examination of parks and arboretums of Kharkiv region (upublished, signed by Prylutska in 1976 and stored in Valkivskyi Local History Museum funds) listed 35 taxa of trees and shrubs (including 13 taxa of conifers).
Finally, Marchuk (2006) inventoried the park dendroflora and reported 69 species and four cultivars. Comparing our recent data with Marchuk's report, we found minor changes in the composition of plantings concerned only the species represented by a small number of individuals.
Some taxa in the Nataliivskyi Park are represented by only a few plants. For example, Betula pendula 'Youngii' is represented by a single old tree, and Acer platanoides 'Cuculatum' -by only two trees. Many trees of Picea abies and P. pungens 'Glauca' were damaged by droughts in 2013, attacked by European spruce bark beetle, and, as a result, died. Most of those dead plants kept standing in their places due to felling prohibition. Today, only solitary trees of P. pungens 'Glauca' survived in the park. Hence, without restorative plantings, taxonomic diversity and projective cover of certain taxa in the park decrease (Table 1).
Today, the dominating species in the Nataliivskyi Park is Pinus sylvestris covering over 50 % of the park's green area. The covering area of P. sylvestris decreased only slightly since 1997 due to the construction of unauthorized roads in the park and its consequent fragmentation. The area of lawns and meadows has significantly decreased. Various self-seeding plants (e.g., Robinia pseudoacacia L. and Acer negundo L.) occupied many open spaces.
Sections without prevailing taxa mainly appeared in the places where edificators fall out of dominance. Since 1997, the area of such sections has increased. In the northern part of the park, one of such sections consists of Acer platanoides, A. negundo, Populus tremula L., and Ulmus laevis Pall. In the central part of the park, such a section includes Catalpa speciosa Teas, Populus × canadensis, Pinus sylvestris, and other taxa. In the southern part of the park, there were small clumps and solitary trees of Tilia cordata, Aesculus hippocastanum, Picea abies, and Pinus nigra J.F. Arnold. Now the space between these trees is filled with Ulmus laevis, Acer platanoides, A. negundo, and other woody plants. In the south-eastern part A. Hryhorenko, Y. Klymenko of the park, there is a section that combines Ulmus laevis, Acer platanoides, A. negundo, Aesculus hippocastanum, Betula pendula, and solitary trees of Pinus sylvestris. Similarly, an orchard in the northern part of the park was overgrown by Ulmus laevis and Robinia pseudoacacia. In general, such species as Ulmus laevis, Robinia pseudoacacia, and Acer negundo actively occupy different areas of the park.
Historical plantings of Quercus robur are extremely valuable; their condition in the park is good. Only in certain oaks, there are tree hollows, there is no significant amount of dry branches in crowns, trees' affection by illness or pests, and there is no trees' dieback. Old trees of Pinus sylvestris, P. nigra, P. strobus, P. abies, Abies concolor, Ulmus laevis, Betula pendula 'Youngii' , Pyrus communis L., and Robinia pseudoacacia preserved in the park too. The plot with Picea pungens 'Glauca' was entirely destroyed by disease and drought, but some old solitary trees of this cultivar preserved in other plots. From opposite, old plantings of Aesculus hippocastanum are currently dying, probably due to low fertility of the sandy soil and lack of moisture (this species is mesophyte requiring other soil conditions) and damage by the leaf-mining moth.
The sylvatic landscape was the primary type in the Nataliivskyi Park back in 1997 (Fig. 3). Inside forests, slight inclusions of the park and regular landscape types were present. True meadows could be found only along the river Merchyk, where the locals regularly mowed the grasses together with young seedlings of the trees. We also attributed to the meadow landscape a large glade (Fig. 3, a). The parterre that used to be in front of the palace disappeared. Only parterre area and alley plantings remained near the park's technical buildings (Fig. 4).
Since 1997, the total area of sylvatic landscape type had significantly increased ( Table 2). The park type of landscapes decreased in certain places but appeared on some formerly open areas. The regular type of landscape is revealed unchanged, but the condition of alleys is imperfect. The parterre area is also overgrowing with self-seeded trees, changing from the regular into the park landscape type. Without mowing, meadows  Dendroflora of the Nataliivskyi Park (Kharkiv region, Ukraine)