14G1

G. Forests

Moesian forests of White oak (Quercus pubescens)

Relationships with habitat classifications. EUNIS: G1.7372 Moesian White oak woods; PAL. CLASS.: 41.7372 Moesian White oak woods; HD 92/43: 91H0 *Pannonian woods with Quercus pubescens; Bondev (1991): 106 Querceta pubescentis and Virgilian oak (Querceta virgiliane) forests, 108 Mixed Virgilian oak (Quercus virgiliana), Quercus pubescens and field maple (Acer campestre) forests, 109 Mixed Quercus pubescens, Virgilian oak (Querceta virgiliana), Silver-leaf lime (Tilia tomentosa) and Flowering ash (Fraxinus ornus) forests, 110 Mixed Quercus pubescens, Virgilian oak (Querceta virgiliana) and Flowering-ash (Fraxinus ornus) forests, 111 Mixed (Quercus pubescens), Virgilian oak (Querceta virgiliana) and Oriental hornbeam (Carpinus orientalis) forests, partly of secondary origin, but only in areas with continental climate – North and West Bulgaria (Sofia region).

Conservation status. BDA, BC, HD.

Category. Endangered [EN – A1, 2 C2 D1 E2 F2 G2 H2 L2].

General characteristics. This habitat is related to the rare, xerothermic oak forests dominated by the white oak (Quercus pubescens). It occurs on calcareous hills in places with continental climate. These forests are a part of the mixed oak forests and usually cover the driest and hottest places on southern and western slopes. The soils are well developed, mostly different types of Luvisols to shallow Lithic Leptosols, Rendzic Leptosol and more rarely Umbric Leptosols. Typically, the soils are dry, relatively poor and eroded to a different degree. Such forests occur mainly in karst areas where the bedrock appears as large rock pieces. As a result of the continental conditions, poor soils and anthropogenic impact the forests are mainly fragmented and in some places are scrub-like. The species composition of the communities of the White oak is very dynamic and diverse. There are many open areas, meadows, stony places that very often form complexes with the xerothermic pastures and scrub. From the latter, very often many xerophytic herbaceous species typical for the geographic region and altitude enter the White oak forests.

The tree layer in which the White oak is a dominant or co-dominant most often reaches 4 – 8 m in height. The trees are branched and often with crooked stems. Apart from Quercus pubescens also Acer campestre, Fraxinus ornus, Quercus cerris, Q. frainetto, Q. virgiliana usually occur in this layer. Carpinus orientalis occurs very often and may form a second tree layer in places with shallow, calcareous soils. The participation of Acer hyrcanum and Acer monspessulanum in such forests in West Forebalkan is of specific interest. The following species occur in the shrub layer: Cornus mas, Cotinus coggygria, Crataegus monogyna, Ligustrum vulgare, Paliurus spina-christi, Prunus spinosa, Rhamnus catharticus, Rosa gallica, Syringa vulgaris, Ulmus minor. The herbaceous layer includes mainly species that are typical for the xerothermic oak forests, such as: Asparagus officinalis, A. tenuifolius, Brachypodium sylvaticum, Buglossoides purpurocaerulea, Dactylis glomerata, Festuca heterophylla, Helleborus odorus, Lactuca quercina, Lathyrus niger, Orchis simia, Potentilla micrantha, Pulmonaria mollis, Scorzonera hispanica, Tanacetum corymbosum, Teucrium chamaedrys, and Trifolium alpestre. Due to its open character and good light the floristic composition of the White oak forests include many species that occur in the meadows and in open places in the forests (e.g. typical for the classes Trifolio-Geranietea and Festuco-Brometea). Such species are Acanthus balcanicus, Althaea cannabina, Bothriochloa ischaemum (= Dichanthium ischaemum), Chrysopogon gryllus, Dictamnus albus, Echinops sphaerocephalus, Euphorbia polychroma, Festuca rupicola, Filipendula vulgaris, Geranium sanguineum, Orchis purpurea, and Primula veris. A beautiful spring aspect during April and May is added by the common peony, Paeonia peregrina. Due to the mild impact of the Black Sea, some Mediterranean species (Asparagus acutifolius, Colutea arborescens, Jasminum fruticans) occur in the isolated White oak forests which have survived in Dobrudzha plateau, e.g. the area of Bolata River (Kavarna region) also. The low mountains in West Bulgaria are characterized by a continental climate but some southern species enter along the valley of Struma River and occur in the rare and light forests of the White oak. The association Genisto lidiae-Quercetum pubescenstis has been described from Golo Bardo Mts. in which species like Ajuga laxmannii, Cotinus coggygria, Festuca rupicola, Fraxinus ornus, Helinathemum nummularium, Tanacetum corymbosum, Teucrium chamaedrys occur. Anthericum ramosum, Asyneuma anthericoides, Coronilla emerus, Eryngium palmatum, Genista subcapitata are widely distributed.

The forests of the White oak participate in complexes with other xerothermic oak forests, i.e. forests of Quercus cerris and Quercus frainetto, as well as with coenoses of Carpinus orientalis. In comparison to the first two species, the White oak is less ecologically sensitive and occurs in places that are less favourable for the others. Sometimes the White oak forests are a degradation stage of their development. Alternatively, the forests of Carpinus orientalis can replace the coenoses of the White oak, particularly in places with advanced erosion and degradation as a result of anthropogenic activities – grazing, logging, fires, etc.

Characteristic taxa.

Distribution in Bulgaria. North Bulgaria – Forebalkan, parts of the Danubian Plain, Northeast Bulgaria, including some places in Dobrudzha area, foothills and low mountains of West Bulgaria: Golo Bardo Mts., southern slopes of Vitosha Mts., Chepan Mts., Konyavska Mts., etc.

Conservation importance. The forests of White oak occur more and more rarely in Bulgaria as a result of logging, grazing, fires, etc. Some rare, endangered and protected species participate in their floristic composition: Chamaecytisus frivaldszkyanus, Eryngium palmatum, Limodorum abortivum, and Polygala supina subsp. murbeckii. These coenoses are an important source of medicinal plants: Paeonia spp., Teucrium spp., Cotynus coggygria, Helleborus odorus, Primula spp., etc. Fungi of conservation importance are Amanita caesarea, A. franchetii, A. strobiliformis, Boletus regius, B. satanas, Geastrum melanocephalum, Leucopaxillus compactus, Sarcosphaera coronaria.

Threats. Clear cuttings and illegal logging; replacement by forest plantations of species not typical for the area (Pinus nigra, P. sylvestris, Robinia pseudacacia), grazing (mainly goats), fires, increase of light and general aridisation of the climate, construction of communication and transport networks and facilities (roads, rail ways, etc.), limestone pits, natural erosion processes on the slopes, etc. In some places the floristic composition of the White oak forests is strongly ruderalized.

Conservation measures taken. The habitat is included in Annex №1 of the Biodiversity Act. Some of the localities are within protected areas: Vrachanski Balkan, Vitosha and Zlatni Pyasatsi Nature Parks and in sites of the European Ecological Network NATURA 2000.

Conservation measures needed. Measures for restoration, mapping and monitoring of all preserved coenoses of the White oak; proclamation of some of the representative coenoses of the White oak as protected areas.

References. Radkov & Minkov 1963; Soo 1957; Velchev 1971.

Authors: Rossen Tzonev, Petar Zhelev, Evgeni Tzavkov


Moesian forests of White oak (Quercus pubescens) (distribution map)