Quercus thracica Stef. & Nedjalkov
Fagaceae – Beech family
Conservation status. Extinct [EX]. BDA. Bulgarian endemic.
Morphology and biology. About 85–90 years old tree. Leaves 4–8(10) cm long, coriaceous, spinose-dentate, overwintering and falling in spring. Male flowers in a catkin, with 3–5 cm long, pubescent peduncle; female flowers in groups of 2(5), with up to 1.5 cm long peduncle. Fruits usually solitary, cupule semispherical, covered with numerous scales. Nut ovoid, c. 2 × 1.5 cm. Fl. V, fruits ripening in October in the second year. Wind pollinated. Produces acorns, dispersed through zoochory and barochory.
Habitats and populations. Only 2 trunks growing about 20 cm from each other have recorded so far. Most likely they belong to one and the same individual. When young, the tree grew in sparse shrubs of Quercus cerris, Q. frainetto, Carpinus orientalis, Juniperus oxycedrus, etc. in the xerothermic oak-forests belt, on siliceous bedrock. Some 45-50 years ago a mixed plantation of Pinus sylvestris and P. nigra was planted around the tree.
Distribution in Bulgaria. Rhodopi Mts (eastern – by the road between Sarnak and Kandilka villages, c. 7–8 km SW of Krumovgrad town); 450 m alt.
General distribution. Bulgaria.
Threats. The extremely small distribution area and presence of only 1 individual, growing in a region with high anthropogenic pressure. In 2000 it was observed that the tree was withering as a result of a fungus desease caused by Hypoxylon mediterraneum and Diplodia mutila. In 2009 complete extinction of the species was recorded.
Conservation measures taken. The species is protected by the Biodiversity Act. The locality is fenced and lies within a site of the European ecological network Natura 2000 in Bulgaria. In 1971 an experimental culture of 45 individuals was established in the Institute of Forestry, Bulgarian Academy of Sciences, on an area of 90 m2. All individuals originated from acorns collected in the field, but due to the hybrid origin of the maternal plant, the progeny is very diverse as a result of hybrid breakdown.
Note.In the Red List of Bulgarian vascular plants the species was evaluated as Critically Endangered [CR B2ab(v); D] (Stanev, 2009).
References. Stefanov & Nedyalkov 1956; Ganchev & Bondev 1966; Stefanov 1972; Nedyalkov 1984; Velchev 1992; Tashev 2002, 2010; Stanev 2009.
Author: Stefan Stanev