16G1

G. Forests

Thracian mixed thermophilic oak forests

Relationships with habitat classifications. EUNIS: G1.761 Helleno-Moesian [Quercus cerris] forests, G1.762 Helleno-Moesian [Ouercus frainetto] forests, G1.76A1 Euxino-Thracian [Quercus frainetto]–[Quercus cerris] forests, G1.76A2 Thracian [Quercus frainetto]–[Quercus virgiliana] forests; PAL. CLASS.: 41.761 Helleno-Moesian [Ouercus cerris] forests, 41.762 Helleno-Moesian [Ouercus frainetto] forests, 41.76A1 Euxino-Thracian [Quercus frainetto]–[Quercus cerris] forests, 41.76A2 Thracian [Quercus frainetto]–[Quercus virgiliana] forests; HD 92/43: 91M0 Pannonian-Balkanic Turkey oak-sessile oak forests; Bondev (1991): 91 Mixed cerris oak (Quercus cerris) and Q. frainetto forests, 92 Mixed Cerris oak (Quercus cerris) and Q. frainetto with Mediterranean elements, 93 Mixed Cerris oak (Quercus cerris), Q. Frainetto and Oriental hornbeam (Carpinus orientalis) forests, partly of secondary origin, 94 Mixed Cerris oak (Quercus cerris), Q. Frainetto and Oriental hornbeam (Carpinus orientalis), with Mdeiterranean elements, partly of secondary origin, 95 Mixed Cerris oak (Quercus cerris) and Q. frainetto forests interspersed with Q. hartwissiana and Oriental hornbeam (Carpinus orientalis), 96 Mixed Cerris oak (Quercus cerris), Q. pubescens and Virgilian oak (Q. virgiliana) forests, 99 Mixed Cerris oak (Quercus cerris) and Oriental hornbeam (Carpinus orientalis), partly also with Flowering ash (Fraxinus ornus), 100 Querceta frainetti forests, 101 Querceta frainetti forests with Mediterranean elements, 102 Mixed Quercus frainetto, Q. pubescens and Virgilian oak Q. virgiliana forests, 103 Mixed Quercus frainetto and Flowering ash (Fraxinus ornus) forests, 104 Mixed Quercus frainetto and Oriental hornbeam (Carpinus orientalis) forests, partly of secondary origin, 105 Mixed Quercus frainetto and Oriental hornbeam (Carpinus orientalis) forests, with Mediterranean elements, partly of secondary origin (in areas of transitional-continental and transitional-Mediterranean climate).

Conservation status. BDA, BC, HD.

Category. Endangered [EN – A1, 2 C1 D1 E2 F2 G2 H2 L3].

General characteristics. This habitat includes the xerothermic, and meso-xerothermic oak forests and oak forests of the hilly plains, foothills and low mountains in South Bulgaria - the southern slopes of the Balkan Range and Sredna Gora Mts., the Thracian Plain, Toundzha Hilly Country, East Rhodopi Mts., Sakar and Strandzha Mts., the valleys of Struma and Mesta rivers, low mountains to the South of Blagoevgrad and Kyustendil. These communities have diverse floristic compositions. Most often they are mixed forests, but in most places Quercus frainetto dominates or forms mixed communities with Quercus cerris and at higher altitudes with Quercus dalechampii. These communities develop mostly on different subtypes of Luvisols, Leptosols, Planosols, Cambisols and in large areas in the southern areas of the country – on shallow Leptosols - Rendzic, Lithosols and Rankers. Such coenoses develop in limited areas in Strandzha Mts. also on Alisols. The soils vary from relatively poor to rich, mostly dry, and with varying degree of erosion. The drought is more intensive during the summer months. The bedrock is mainly silicate, but in some places can be carbonate as well. The Thracian oak forests occupy slopes of different exposures and the tops of hills. As the erosion increases, in the driest and poorest areas, these coenoses are replaced by communities dominated by Acer monspessulanum, Carpinus orientalis, Quercus pubescens. In places with extremely degraded soils they are replaced by communities of Bothriochloa ischaemum (= Dichanthium ischaemum), Chrysopogon gryllus, Juniperus oxycedrus, and Paliurus spina-christi.

There is enough light in the Thracian mixed thermophilic oak forests (canopy of 0,6–0,7), and hence the participation of many tree, shrub and herbaceous species is possible. The tree layer reaches the average of 8–12 m. In the mixed coenoses of Quercus cerris and Quercus frainetto usually the first is more abundant. Quercus frainetto occupies drier and warmer places compared to Quercus cerris. The latter occurs in Stara Zagora district and in the xeromesophytic coenoses of Quercus pedunculiflora. Acer campestre, A. hyrcanum, A. monspessulanum, A. tataricum, Fraxinus ornus, Pistacia terebinthus, Q. dalechampii, Q. pubescens, Q. virgiliana also participate in the tree layer. As a result of the anthropogenic and natural soil erosion Carpinus orientalis very frequently participates in these coenoses and can form a second tree layer that is 3–4 m high. The shrub layer often includes Colutea arborescens, Cornus sanguinea, Coronilla emerus subsp. emeroides, Cotinus coggygria, Crataegus monogyna, Juniperus oxycedrus, Lonicera etrusca, Paliurus spina-christi and more rarely, in the most southern areas, Phillyrea latifolia. The herbaceous layer of the Thracian mixed thermophilic oak forests consists mainly of species typical for the xerothermic oak forests. The number of the Mediterranean floristic elements increase southwards. These rich species complex include Aristella bromoides (= Stipa bromoides), Brachypodium pinnatum, B. sylvaticum, Buglossoides purpurocaerulea, Comandra elegans, Dactylis glomerata subsp. lobata, Dictamnus albus, Festuca heterophylla, Geranium sanguineum, Helleborus odorus, Lathyrus niger, Physospermum cornubiensis, Potentilla micrantha, Tanacetum corymbosum, Teucrium chamaedrys, Trifolium alpestre, and Verbascum phoeniceum.

The thermophilic oak forests on the low hills of the Thracian Plain, Toundzha Hilly Country and the southern slopes of Sredna Gora Mts. (Stara Zagora region), have transitional characteristics between the continental and transitional-Mediterranean thermophilic oak forests. They include mainly widespread species typical of xerothermic oak forests and are floristically closer to the communities of that type that occur in North Bulgaria. Some Mediterranean elements that cannot be found in the similar coenoses in North Bulgaria also rarely occur, such as Arum orientale, Clematis viticella, Digitalis ferruginea, Fritillaria pontica, Genista carinalis, Hypericum montbretii, Lonicera etrusca, and Scilla autumnalis.

The forests in East Rhodopi Mts are very typical. They include many typical Mediterranean and endemic species. There, in the mixed thermophilic oak forests where the light is strong enough, a shrub layer of Juniperus oxycedrus, Rubus sanguineus, and Paliurus spina-christi develops. The endemic species Stefanoffia daucoides also occurs relatively rarely in some places. Huetia cynapioides forms a typical early-summer flowering aspect in the forests of Quercus frainetto in the Struma River valley.

Thracian thermophilic mixed oak forests are part of the alliance Quercion frainetto and of the large polymorphic association Quercetum frainetto-cerris s. l., represented by different geographical synvicariants in the various parts of the Balkan Peninsula. In Bulgaria, they may be affiliated to the geographic syntaxon Quercetum frainetto-cerris thracicum. The Thracian thermophilic oak forests are usually found in complexes with other xerothermic oak forests – with Quercus pubescens, Carpinus orientalis, and in the Kresna Gorge, with Juniperus excelsa. Everywhere they are influenced by anthropogenic activities - grazing, felling, burning; therefore they have altered species compositions and varying degrees of degradation.

Characteristic taxa.

Distribution in Bulgaria. South Bulgaria – southern slopes of the Balkan Range and Sredna Gora Mts., Thracian Plain and Toundzha Hilly Country, East Rhodopi Mts., Sakar Mts., Strandzha Mts., the valleys of Struma and Mesta rivers; up 800 (1000) m alt.

Conservation importance. This habitat is subjected to very strong anthropogenic pressure – felling, grazing, fires, etc. Some rare and endangered vascular plants occur in them like Andrachne telephioides, Aristolochia rotunda, Carduus thracicus, Carex punctata, Fritillaria pontica, Heptaptera triquetra, Huetia cynapioides, Ononis adenotricha, Smyrnium rotundifolium, Stefanoffia daucoides, Vicia laeta, as well as some fungi of conservation importance: Amanita caesarea, A. franchetii, A. ovoidea, A. strobiliformis, Boletus armeniacus, B. caucasicus, B. dupainii, B. parasiticus, B. permagnificus, B. persicolor, B. radicans, B. regius, B. rhodopurpureus, B. rhodoxanthus, B. satanas, Clavariadelphus pistillaris, Cortinarius bulliardii, C. coerulescens, Helvella atra, Hericium erinaceum, Hygrophorus arbustivus, H. russula, Lactarius acerrimus, Rubinoboletus rubinus, and Tricholoma acerbum.

Threats. Large-scale clear cuttings and illegal felling associated with excessive use of wood for heating. In East Rhodopi Mts. the wood is used to produce charcoal. Other negative factors are the replacement of natural forests by plantations of trees not typical for the areas (Black and Scots pine, Locust tree); grazing of livestock (mainly goats); fires; drought and the general aridisation of the climate; slow restoration of the forests and some fungal diseases that affect shoots; natural erosion on the slopes; open method of the extraction of natural resources.

Conservation measures taken. The habitat is included in Annex № 1 of the Biodiversity Act. Parts of these forests are in protected areas – the areas around Madzharovo and Studen Kladenets dam, Strandzha Nature Park, Meandrite na Byala Reka Protected Site, Tisata and Ropotamo Strict Nature Reserves. Some of the most representative localities are in sites of the European Ecological Network NATURA 2000: East Rhodopi, Kresna sites, etc.

Conservation measures needed. Legislation amendment in order to stop the clear cuttings, especially in private forests, and eliminate the use of the oak forests for charcoal. Termination of the felling for reconstruction. Use of the natural forest restoration potential for converting them into seed forests by applying of the selection patch clear cuting, that is most suitable for the oak forests. Develop a system to subsidize the forest owners who implement environmentally friendly practices for forest management. Restoration activities, incl. support for the seed reproduction and fighting the fungal diseases of the shoots. Proclamation as protected areas of some of the most representative coenoses of Quercus frainetto and Q. cerris.

References. Ganchev 1965; Meshinev et al. 1982; Radkov & Minkov 1963.

Authors: Rossen Tzonev, Georgi Gugushev, Petar Zhelev


Thracian mixed thermophilicoak forests (distribution map)