Epiphytic bryophytes of the State Dendrological Park “Olexandria” of the NAS of Ukraine

Investigations of the species diversity of epiphytic bryophytes of the State Dendrological Park “Olexandria” (the historical part and the “Budynok Lisnyka” plot) were conducted in 2017–2019 and revealed 40 species representing 22 genera, 17 families, seven orders, two classes, and two divisions. This corresponds to 46.51 % of the total number of detected bryophytes in the park. The leading families in the bryoflora of the park are Orthotrichaceae (9 species), Brachytheciaceae (6), Amblystegiaceae (3), Anomodontaceae (3), Dicranaceae (3), Hypnaceae (3), and Pottiaceae (2). The leading genera are Orthotrichum (9 species), Anomodon (3), and Dicranum (3). Among the identified taxa, five species (Dicranum tauricum, Orthotrichum lyellii, Porella platyphylla, Sciuro-hypnum reflexum, and Syntrichia virescens) are regionally rare within the Forest-Steppe zone of Ukraine. Most of the recorded epiphytic mosses were found on the bark of Acer platanoides (28 species), Fraxinus excelsior (27), Quercus robur (26), Acer campestre (23), and Tilia cordata (22). The least epiphytic mosses were found on the bark of conifers (Pinus sylvestris, P. strobus, Picea abies, Larix decidua, etc.). The surveyed trees in the State Dendrological Park “Olexandria” were also found such epigeal mosses as Plagiomnium cuspidatum, Ceratodon purpureus, Dicranella heteromalla, and Pohlia nutans, as well as epixilic moss Dicranum flagellare, etc. The “Budynok Lisnyka” plot hosts three species that do not occur in the park’s historical part. In particular, Lophocolea heterophylla and Sciuro-hypnum curtum were found there on Quercus robur trunks and Sciuro-hypnum reflexum on Quercus rubra bark. At the same time, the historical part of the park is characterized by the number of expansive bryophytes.


Introduction
Biodiversity conservation is one of the essential tasks to be completed, mainly through the nature conservation areas. One of such areas is the State Dendrological Park "Olexandria" of the NAS of Ukraine, established in 1788. At present, there are registered over 3100 species of arboreal plants and over 1500 herbs. However, the diversity of bryophytes of the park is still insufficiently investigated. Hence, our research's objective was to reveal the taxonomic diversity of epiphytic bryophytes in this park.
Epiphytic bryophytes of the State Dendrological Park "Olexandria" of the NAS of Ukraine

Results and discussion
Our research results showed that the epiphytic bryoflora of the State Dendrological Park "Olexandria" comprises 40 species belonging to 22 genera, 17 families, seven orders, two classes, and two divisions (Table 1).
The historical part of the State Dendrological Park "Olexandria" counts 37 epiphytic bryophytes and the "Budynok Lisnyka" plot -23 taxa. In the "Budynok Lisnyka" plot, there are unique species that do not occur in the historic part of the park. In particular, Lophocolea heterophylla and Sciuro-hypnum curtum were found there on Quercus robur trunks and S. reflexum on Quercus rubra L. bark. At the same time, the historical part of the park hosts many expansive bryophytes.
The most common mosses on the bark of Tilia cordata were Hypnum cupressiforme,  (Fig. 3).
Epiphytic bryophytes of the State Dendrological Park "Olexandria" of the NAS of Ukraine   (Fig. 3). However, some bryophytes occurred exclusively on certain tree species. For example, Dicranum scoparium and D. tauricum were found only on the bark of Betula pendula; Brachythecium rutabulum -exclusively on the bark of Acer platanoides; Frullania dilatata, Sciuro-hypnum curtum, and Lophocolea heterophylla -on the bark of Quercus robur; Sciuro-hypnum reflexum -on the bark Quercus rubra; Orthotrichum striatum -on the trunk of Fraxinus excelsior.
The richness of bryophytes on introduced trees was lower than on the native arboreal species. Thus, Acer pseudoplatanus hosted only 15 species of epiphytic bryophytes, while A. platanoides -28 species, and A. campestre -23 species. Quercus rubra hosted 11 species, while Q. robur 26 species. On the bark of Robinia pseudoacacia we have found 13 species of bryophytes, on Aesculus hippocastanum -11 species, and on Catalpa ovata G. Don. -eight species (Fig. 4). On the trunks of such broad-leaved species as Platanus × acerifolia (Ait.) Willd. and Juglans cinerea L. we have found only five species of bryophytes per each tree species, on Cercidiphyllum japonicum Sieb. et Zucc. and Juglans nigra L. -four species, on Celtis mississipiensis Bosc. and Gleditsia triacanthos L. -three species. Lower species diversity of mosses on some introduced plants is probably related to their bark properties and the conditions of growing. In the State Dendrological Park "Olexandria" they were mostly planted as solitary trees or in small curtains on the lawns. Hence, such plants grow in good light, which, however, results in conditions that are not optimal for the development of most mosses.
Nevertheless, the smallest number of epiphytes occurred on the bark of conifers. Thus, on the bark of Pinus sylvestris L. we recorded only four species of mosses, on the bark of Pinus strobus L., Picea abies (L.) Karst., Larix decidua Mill. and some others -only two species. This is because their bark, unlike most deciduous trees, has higher acidity (Insarova & Insarov, 1989). Moreover, conifers constantly shed their bark, which explains the absence or a low number of hosted bryophytes (Sluka, 1975;Dymytrova, 2008).

Conclusions
Our study showed that epiphytic bryoflora of the State Dendrological Park "Olexandria" includes 40 species, which corresponds to