21G1
Hop-hornbeam (Ostrya carpinifolia) woods
Relationships with habitat classifications. EUNIS: G1.7C12 Supra Mediterranean Hop-hornbeam woods, G1.7C13 Montane Hop-hornbeam woods; PAL. CLASS.: 41.812 Supra Mediterranean Hop-hornbeam woods, 41.813 Montane Hop-hornbeam woods; Bondev (1991): 47 Mixed Mizian oak (Fagus sylvatica subsp. moesiaca) and Aquatic hornbeam (Ostrya carpinifolia) forests, 64 Aquatic hornbeam (Ostryeta carpinifoliae), forests and shrubs, partly of secondary origin, 67 Black pine (Pinus nigra) and Aquatic hornbeam (Ostrya carpinifolia) forests.
Conservation status. BC.
Category. Vulnerable [VU – A1 B2 C1 D2 E2 F1 G1 H2I L2].
General characteristics. The area of distribution of the Tertiary relic Hop-hornbeam (Ostrya carpinifolia) covers the Southwest part of Europe (the species occurs also in Southwest Asia) and falls within the borders of the Adriatic-Illyrian region. The localities in Bulgaria are in the western part of this area, in a region with sub-Mediterranean influence. The communities of this species are best represented in Rhodopi Mts., along Chaya, Vacha and Chepinska rivers, near Smolyan; on the slopes of the valley of Mets river; on the slopes of Slavyanka Mts.; in the valleys from the water catchment of Struma river (Sandanska Bistritsa and Blagoevgradska Bistritsa rivers, Kresna and Zemen gorges, Vlachina Mts.). They occur also in Sredna Gora Mts., on the southern slopes of Central Balkan Range and in the valley of Osam River (Troyan region) etc.
The Hop-hornbeam makes both forest and shrub coenoses mainly on limestone and rarely on silicate. The areas are mainly rocky; the soil cover is poorly developed. The soils are of Leptosols Rendzic type. The coenoses occur mainly on steep, preferably northern slopes, and in deep ravines with humid air and soils. A considerable part of the coenoses is of primary origin but in some places communities of secondary origin also occur. In Rhodopi Mts., Ostrya carpinifolia participates or completely constitutes the shrub layer in Black pine forests. When the Black pine forests are cut down secondary coenoses of Ostrya carpinifolia develop.
The coenoses of Ostrya carpinifolia cover largest areas in the foothills and the lower parts of the mountains in the belt of the mesophilic hornbeam and beech forests up to 900 m alt., rarely reaching 1300–1400 m alt. The various climatic conditions due to the different latitude (continental or sub-Mediterranean climate) and altitude (the belt of xerothermic oak forests and the mesophilic hornbeam-beech forests) are reflected in the peculiarities of the floristic composition and structure of these coenoses. The differences in the floristic composition of the coenoses that develop at different ecological conditions are the basis for the identification of two groups (with transitions between them): sub-Mediterranean and mountain coenoses of Hop-hornbeam. The phytocoenoses that occur below 900 m alt. are mostly related to the sub-Mediterranean type. Monodiminant coenoses are relatively rarer compared to the polydominant ones. The areas in Slavyanka Mts. and some parts of Rhodopi Mts. are richer in species, with different abundances of codominants such as Carpinus orientalis, Fraxinus ornus, Pinus nigra, Quercus pubescens. The shrub layer includes Cornus mas, C. sanguinea, Corylus avellana, Cotinus coggygria, Cotoneaster nebrodensis, Juniperus oxycedrus, Paliurus spina-christi, and Syringa vulgaris. In the more southwestern parts of the country where the sub-Mediterranean influence is stronger some southern species also occur such as Coronilla emerus, Pistacia terebinthus etc. The shrub species do not always constitute a consistent layer. The herbaceous layer as a rule has a high projective cover. It is more closely related to the rocks and includes a number of skiophytes that distinguishes the coenoses of the Hop-hornbeam from the neighbouring coenoses of the White oak (Quercus pubescens). Some of the most widely distributed species, often with high abundances, are Aremonia agrimonoides, Brachypodium pinnatum, Luzula luzuloides, Melica uniflora, Poa nemoralis etc.In some places in Rhodopi Mts also occur the Tertiary relic Haberlea rhodopensis. These coenoses can be affiliated to the alliance of Ostryo-Carpinion orientalis, which occurs widely on the territory of former Yugoslavia and Greece.
The coenoses that occur in more mesophytic conditions, mainly above 900 m alt., are a part of the mountain belt and include more species typical for the hornbeam-beech forests: Quercus dalechampii, and more limited Acer hyrcanum, Carpinus betulus, Fagus sylvatica, Fraxinus excelsior. The herbaceous layer includes Hedera helix, Mercurialis perennis, Polypodium vulgare, Tamus communis etc. The sub-Mediterranean species disappear and the mesophytic features prevail in the coenoses.
Characteristic taxa.
- Vascular plants: Acer hyrcanum, Aremonia agrimonoides, Brachypodium pinnatum, Carpinus betulus, C. orientalis, Cornus mas, C. sanguinea, Corylus avellana, Cotinus coggygria, Cotoneaster nebrodensis, Fagus sylvatica, Fraxinus ornus, Haberlea rhodopensis, Hedera helix, Juniperus oxycedrus, Luzula luzuloides, Melica uniflora, Mercurialis perennis, Paliurus spina-christi, Pinus nigra, Poa nemoralis, Polypodium vulgare, Quercus dalechampii, Q. pubescens, Syringa vulgaris, Tamus communis.
- Fungi: Macromycetes – Boletus depilatus, Inonotus hispidus;Micromycetes – Apiognomonia ostryae, Plagiostoma arnstadtiense (on Ostrya carpinifolia), Ascochyta syringae, Phyllactinia fraxini (on Fraxinus excelsior), Microsphaera alphitoides (on Quercus cerris and Q. frainetto), Phyllactinia guttata, Sawadaea bicornis (on Acer hyrcanum).
- Animals – Chiroptera: Nyctalus noctula, Eptesicus serotinus, Pipistrellus pipistrellus, Hypsugo savii, Myotis mystacinus, Myotis capaccinii, Barbastella barbastellus.
Distribution in Bulgaria. Rhodopi Mts. – along Chaya, Vacha and Chepinska rivers, near Smolyan; on the slopes of the valley of Mesta river (Momina Klisura locality); on the slopes of Slavyanka Mts.; in the valleys from the water catchment of Struma river (Sandanska Bistritsa and Blagoevgradska Bistritsa rivers, Kresna and Zemen gorges, Vlachina Mts.). They occur also in Sredna Gora Mts., on the southern slopes of Central Balkan Range, Troyan Balkan Range, etc.
Conservation importance. Part of the communities are of primary origin and play a role in soil formation and soil protection. These conenose are part of the sub-Mediterranean vegetation in Bulgaria and include some southern species like Coronilla emerus, Pistacia terebinthus, etc. the rare species– Haberlea rhodopensis etc. and Boletus depilatus – a fungal species of conservation importance.
Threats. Logging, fires, infrastructure developments.
Conservation measures taken. A small part of this habitat is within protected areas – Central Balkan National Park and sites from the European Ecological Network NATURA 2000.
Conservation measures needed. Detailed phytocoenological and hydrological studies. Expanding the borders of the existing protected areas, more efficient and nature-friendly management, mapping and monitoring of the better-preserved coenoses, restoration of destroyed habitats and phytocoenoses.
References. Gorunova & Kochev 1992; Kochev 1969; Nikolov & Nikolov 1984.
Authors: Veska Roussakova, Alexander Tashev
