DENDROFLORA OF CALCAREOUS TERRAINS IN BULGARIA AND ITS SIGNIFICANCE FOR CONSERVATION

The work presents characteristics of calciphile species from the dendroflora of Bulgaria (107 species), both facultative (77 species) and obligated (30 species) – their systematic structure according to families and genera, division according to biological types and live forms, as well as floristic geo-elements and spreading on vertical belts and floristic regions in Bulgaria. The conservation significance of calciphiles at national and international level has been shown on the basis of referent documents. A systematic list of calciphile species of the Bulgarian dendroflora has been presented.


Nature Conservation Research. Заповедная наука 2016. 1 (3): 70-77
When compiling the list, all species were divided into 2 groups: 1) obligate calciphiles (o) or species known only in calcareous habitats in the country; 2) facultative calciphiles (f) or species known mostly from limestones (Velchev, 1998).The list contains 107 species belonging to 57 genera and 27 families (Table 1).Of them, 30 species are classified as obligate calciphiles, and 77 species as facultative calciphiles.This amounts 24.8% of the species, 38.5% of the genera and 45.0% of the families of the Bulgarian dendroflora, as well as 26% of the species, 6.2% of the genera and 17.4% of the families of the whole Bulgarian flora.The Pinophyta include six species belonging to two genera and two families, while the Magnoliophyta include 101 species belonging to 55 genera and 25 families.Amongst the families, the Fabaceae is represented by 23 species, followed by Rosaceae -22 species, Lamiaceae -11 species, Rhamnaceae -6 species, Brassicaceae, Salicaceae, Cupressaceae and Thymeleaceae -4 species each, Oleaceae and Cistaceae -3 species each, Betulaceae, Pinaceae, Cornaceae, Anacardiaceae, Aceraceae and Rutaceae -2 species each.Eleven families include one species each.Amongst the genera, Chamaecytisus is represented by the highest number (7) of species, followed by Rosa and Genista -6 species each, Sorbus and Satureja -5 species each, Daphne, Salix, Rhamnus, Thymus and Juniperus -4 species each, Corothamnus -3 species, Rhodax, Cornus, Mattiola, Crataegus, Pinus, Iberis, Prunus, Cotoneaster and Acer -2 species each.The other 35 genera are represented by one species each.
According to the classification of life forms after Raunkiaer (1934) phanerophytes (Ph) are represented by 72 species, chamaephytes (Ch) by 13; other species may move from one group to another, including 15 species, which could be hemicryptophytes (H) (i.e.perennial herbs) under certain conditions (Table 2).
According to the classification of phytogeographic elements after B. Stefanoff (1943) stationary and mobile thermophytes, mesotherms, microtherms from Mountainous Centre predominate -75 species, followed by stationary thermophytes from the Mediterranean Centre -14 species, stationary and mobile mesotherms from the Sylvic-Boreal Centre (8 species), stationary and movable thermophytes from the Northern Continental Centre (area of the South Russian Plain) -6 species, and stationary and movable thermophytes from the Southern Continental Centre -4 species.Moreover, from the 107 species, 99 (92.5%) are stationary plants, and only eight species are movable plants having a wider range of ecological niche.There are neither secondary nor alien species within the studied group of arboreal plants.This proves their strong confinement to the calcareous rocks.
Depending on the vertical distribution in the country, plant species living within an altitudinal belt from 0 to 600 m above sea level predominate (82 species), followed by the altitudinal belt 600-1000 m a.s.l.-77 species, 1000-1500 m a.s.l.-66 species, 1500-2000 m a.s.l.-36 species, 2000-2500 m a.s.l.-19 species.Only nine species are known within the altitudinal belt from 2500 to 2900 m a.s.l.Fig. 3 (blue line) represents the relationship between the vertical distribution of the calcareous dendroflora along altitudinal belts.The empirical relationship is y = -16.257x+ 105.07,where y is the number of species, and x is the altitudinal belt.The regression coefficient is R 2 = 0.9582.
Amongst the 20 floristic regions of Bulgaria (Fig. 4), the highest number of calciphile species has been registered in the Rhodopes (81 species -75.7% of the total number of calciphile species in Bulgaria's dendroflora), followed by 77 species (72.0%) in Stara Planina Mt. (Balkan Range) (Fig. 1.), 63 species (58.9%) in Pirin Mt. (Fig. 5.), 56 species -in Slavianka Mt., Znepole region -55 species, Thracian Plain -53 species, Rila Mt. -51 species, the Black Sea coast -49 species, North-Eastern Bulgaria and Fore-Balkan region -47 species each, the Tundzha Hilly Plain -46 species, Vitosha region -45 species, the Struma valley and Sredna Gora Mt. -41 species each, the Danubian Plain -40 species, West Frontier Mountains -39 species, Strandzha Mt. -35 species, Belasitsa Mt. and the Mesta River Valley -33 species each, and the smallest species number (31) is found in the region Sofia.There are 9 species registered only in one certain floristic region, 12 species -only in two certain regions, 5 species are specific for three floristic regions, 11 species -for 4 regions, 8 species -for five floristic regions, etc.There are 20 calciphile species of Bulgaria's dendroflora which are known in all 20 floristic regions.The dendroflora of the calcareous terrains has a large significance for nature conservation.The Red Data Book of the Republic of Bulgaria (Peev, 2015) contains data about 13 of the investigated species: Aesculus hippocastanum, Astracantha thracica, Caragana frutex, Chamaecytisus kovacevii, Convolvulus  Obligate calciphiles in the Bulgarian dendroflora are presented by 30 species belonging to 24 genera and 15 families, which represent 6.9% species, 16.2% genera and 25.0% families of the total number of species in the Bulgarian dendroflora.The Pinophyta include one species, while the Magnoliophyta include 29 species, belonging to 23 genera and 15 families.Amongst the families, the Fabaceae and Lamiaceae contain the highest number of species (6 species each), followed by Rosaceae (4 species), Cistaceae -2 species.The other 13 families are represented by one species.Amongst the genera, Thymus includes the highest number of species (3), followed by Rosa, Rodax, Chamaecytis-sus and Satureja (2 species each).The other 20 genera contain one species each.

Nature Conservation
The biological types are distributed as following: 14 species are shrubs, 8 species -semi-shrubs or perennial herbs, 4 species -semi-shrubs, and 3 species -trees.The Phanerophytes (Ph) are represented by 14 species, the Chamaephytes (Ch) -by 7, the other 8 species may vary from one group to another, including 7 species, which may be hemicryptophytes (H) (i.e.perennial herbs) under certain conditions (Raunkiaer, 1934) (Table 2).

Nature Conservation
The group of obligate calciphiles in the Bulgarian dendroflora also has a large significance for nature conservation.The Red Data Book of the Republic of Bulgaria (Peev, 2015) contains data about 7 (24.1% of the total number of obligate calciphile species in the Bulgarian dendroflora) of the investigated species:  The presented data show that the calciphile Bulgarian dendroflora includes more than a quarter of the entire Bulgarian dendroflora.Species of the families Fabaceae, Rosaceae and of the genera Chamaecytisus, Genista and Rosa predominate.Shrubs predominate amongst the biological types, and phanerophytes are presented by the highest number of species amongst life form groups.
The geo-elements of the flora are represented mostly by stationary thermophilous species of Mediterranean origin that occur primarily in the lowest altitudinal belt.Pronounced linear relationship exists between the amount of calciphile plants in different vertical belts.Amongst the Bulgarian floristic regions, the majority of calciphile plants is known from the Rhodopes, Stara Planina Mt. (Balkan Range) and Pirin Mt., 19 calciphile species are known in all floristic regions, and 9 species -only in one certain floristic region.
The calciphile dendroflora has significant importance for nature conservation not only for Bulgaria but also for Europe as a whole.Being included in all analysed lists, Viola delphinantha is the most valuable species; it has a very high conservation value.The studied groups of plants include many tertiary relicts, endemics, ornamental, melliferous and medicinal plants.

Fig. 2 .
Fig.2.Distribution of calciphile species of Bulgarian dendroflora according to biological types.
Fig. 3 (brown line) represents the vertical distribution of the obligate calciphile arboreal plants along altitudinal belts.The empirical relationship is y = -3.0571x+ 23.533, where y is the number of species, and x is the altitudinal belt.The regression coefficient is R² = 0.9574.