Plant Community Ecology in Bulgaria

Tenio Meshinev, Velcho Velchev, Pavel Vassilev, Iva Apostolova, Nikolay Georgiev, and Anna Ganeva

Summary

In Bulgaria, systematic research in the field of plant community ecology began in the early 1950s and is now in a period of rapid development. Detailed information about the composition, structure, and distribution of plant communities is available for much of the country. However, some areas remain less thoroughly studied, including the Rhodope Mountains, the northern flank of the Stara Planina and Pirin Mountains, the Black Sea region, and the steppe elements in northeastern Bulgaria. Moreover, study results, where they are available, are often marred as a result of insufficient equipment and limited possibilities for comparison with other Balkan and European countries (due primarily to differences in phytocenological schools). Publication of scientific information is hindered by grave financial conditions and other difficulties.

Plant ecologists have so far described 1,000 plant associations, belonging to about 800 formations, in Bulgaria. A number of these are relict and endemic communities, and rare in Bulgaria. Bulgarian endemic species prevail in 27 communities, while Balkan endemics predominate in 77 others. The greatest variety of habitats and plant communities occurs in the larger Bulgarian mountain ranges: the Stara Planina, Rila, Pirin, Rhodope, Slavyanka, and Strandzha. In general, human activity has affected these communities less extensively than others. Other communities that are highly valuable from a conservation standpoint include: sand dunes and other habitats along the Black Sea coast; longose forests; steppe communities; the Mediterranean elements in the valleys of the Strouma and Mesta Rivers; mesophytic meadows in the plains; and macrophytic vegetation around water basins. These communities are among those that have been most severely affected by human activity.

The most significant threats to natural vegetation in Bulgaria are: extensive logging; the replacement of natural forest communities by plantations of Pinus sylvestris and Pinus nigra; unrestricted grazing; construction and urban development; and pollution from industry, transport, and household waste. In order to address these threats and protect biodiversity within Bulgaria's plant communities, conservation strategies should be based on the theoretical principles of modern ecology.

A Brief History of Plant Community Ecology in Bulgaria

In Bulgaria, plant community ecology (or phytocenology) became an autonomous branch of science about 1950. Prior to that, information about phytocenology was found primarily in phytogeographic and forestry studies. The findings in some of these early studies closely resemble those reported in the latest research on plant communities. Early information about phytocenology can also be found in the publications of the many authors who worked in this field before 1950. Of particular note are the works of Davidov (1912), Adamovich (1909), Stoyanov (1922, 1926, 1927, 1928, 1929, 1941), Stefanov (1923), and Yordanov (1931, 1936, 1939, 1944).

The works of Stoyanov were especially important. He studied the vegetation of Alibotoush (1922), the origin of the xerothermic plant element (1926), Bulgaria's riparian forests (1928, 1929), and the characteristics of Bulgaria's major phytocenoses (1941). Equally important were the works of Stefanov on phytogeographic elements in Bulgaria (1943), torfaceous vegetation (1931), the occurrence of steppe vegetation (1936), and plant interactions in the Bulgarian part of Strandzha Mountain (1939).

Most phytocenological studies in the 1950s investigated the composition, structure, distribution, and dynamics of plant communities, and the influence of environmental conditions on community characteristics. This approach continued to develop in the following decades.

At first, systematic phytocenological research concentrated on the study of meadow and pasture vegetation. The results were published in the monograph Meadow and Pasture Vegetation in Bulgaria (1964). At the same time (especially in the 1960s), research was begun on the vegetation of specific mountains or parts of mountains, as well as some plains areas. These can be regarded as regional phytocenological studies. Typical examples include studies of the vegetation of: the eastern part of Lyulin Mountain (Ganchev, 1952); Golo Bardo (Stoyanov and Ahtarov, 1953); southern Dobroudzha (Stoyanov et al., 1955); the Elena part of the Stara Planina Mountains (Stoyanov et al., 1955); the regions of Troyan and Teteven (Velchev, 1958); the Ograzhden Mountain and valley of the Strouma River (Ganchev, 1958); the eastern Rilas (Bondev, 1959); Lozen Mountain (Ganchev, 1961); the region of Dragoman-Belediehan (Velchev, 1962); the northwestern Rilas (Ganchev, 1963); the Stara Zagora lowlands (Ganchev, 1965a, 1965b); Berkovska and Chiprovska Mountains (Bondev, 1966); the Troyan part of the Stara Planina Mountains (Kochev, 1969); and Vrachanska Mountain (Velchev, 1971).

Research also focused on separate ecological vegetation types. Examples include: ephemeroid vegetation in the southern parts of the country (Stoyanov and Ahtarov, 1951); halophytic vegetation in Bulgaria (Ganchev et al., 1971); hygrophytic and mesohygrophytic vegetation in the Palakaria River valley (Drazheva, 1963); psammophytic and other vegetation in the Black Sea region (Velchev and Bondev, 1982; Meshinev et al., 1982); and macrophytic vegetation around water basins (Yordanov and Kochev, 1976; Kochev, 1983; Kochev, 1989).

Research also focused on formations and associations of special interest to science, especially those that contained: relict, endemic, rare, and threatened species for Bulgaria and for the Balkan Peninsula as a whole: Acer monspessulanum in northwestern Bulgaria (Velchev et al., 1965); Kentranthus kellereri (Velchev and Vassilev, 1970); Convolvulus compactus (Velchev, 1970); Astragalus augustifolius (Velchev and Vassilev, 1984); Ramonda serbica (Velchev et al., 1973); Pinus peuce in the Stara Planina Mountains (Velchev, 1973); Aesculus hippocastanum (Kochev and Gorounova, 1972); Juniperus excelsa (Velchev et al., 1984); Astragalus aitosensis (Velchev and Bondev, 1975); Pancratium maritimum (Velchev and Vassilev, 1976); and Potentilla fruticosa (Meshinev, 1973; Meshinev, 1975). These works contributed significantly to the establishment of the composition and distribution of these plant taxa, to our understanding of the ecological conditions under which they occur, and to our appreciation of problems related to their conservation.

The first published maps of Bulgarian vegetation were produced in the late 1960s (Bondev et al., 1969). These maps laid the foundation for the application of cartographic methods in the study of vegetation and plant ecology. Subsequently, large-scale maps of the vegetation of separate regions (Velchev, 1971; Roussakova, 1986; Kochev, 1976) and small-scale maps of the vegetation of the country as a whole (Bondev, 1973; Bondev, 1991) were prepared. In connection with these efforts, information was published on primary and secondary vegetation in Bulgaria (Bondev, 1973a) and on edificators and dominants in the country's vegetation cover (Bondev, 1973b). In retrospect, the production of these maps and the publication of this scientific information were of great significance. This work provided the scientific basis for programs and plans for the rational use, management, and protection of Bulgaria's natural vegetation.

Over the last fifteen years, studies related to environmental protection have gained a central position in Bulgarian phytocenology. These studies have examined several issues of critical importance, including the influence of pollution on plant communities, the negative impact of other anthropogenic factors, and the vegetation of protected areas (e.g., Bondev et al., 1980; Vassilev, 1980; Bondev and Velchev, 1977; Meshinev et al., 1982; Velchev and Vassilev, 1983; Bondev et al., 1983; Velchev et al., 1983; Kochev et al., 1983; Meshinev and Katerova, 1983; Meshinev and Vassilev, 1983; Velchev and Bondev, 1984a, 1984b; Nikolov and Nikolov, 1984; Velchev et al., 1985; Velchev et al., 1985; Meshinev, 1985; Meshinev and Todorova, 1985). It was during this same period that the first program for complex ecological research using permanent experimental sites was established (Velchev et al., 1983). Also important in this regard are the works of Velchev and Bondev (1985), Velchev (1962, 1971, 1983), and Velchev et al. (1989), which are synoptic and problem-raising in character.

This brief survey does not embrace a number of phytocenological works related to the study of biological productivity, metabolism, and other aspects of plant ecology. We believe that, important though this work has been, it is less directly relevant to the development of a National Biological Diversity Conservation Strategy.

Major Gaps in Knowledge and Research Needs

As the above review indicates, the study of plant community ecology in Bulgaria has made remarkable progress in recent decades. Extensive information about the composition, structure, and distribution of the major plant communities has been gained. There are highly competent experts in the research institutes who continue to conduct research in this field. But while acknowledging that we have a wealth of available information, we should also note that certain gaps exist. These shortcomings are understandable at the present stage of research, and should draw the attention of future researchers:

• First and foremost, we lack complete systematic information and a full inventory of the vegetation in Bulgaria.
  
  
• While the small-scale vegetation maps are indeed useful, their use is limited. A large-scale (M=1:200,000) vegetation map project that has been underway for several decades now has run into serious difficulties. Its progress is very slow and in the last few years has come to a virtual standstill due to a lack of funds.
  
  
• Our knowledge of the different plant communities in Bulgaria was accumulated over a long period of time, while anthropogenic changes have taken place very quickly. Thus, some of the available results are of only historical value. In a number of cases they are of little use in comparative analyses.
  
  
• Because of past restrictions and present financial difficulties, our knowledge of the vegetation of neighboring countries is very poor. It is virtually impossible to understand the laws of plant community distribution in the Balkans if scientists cannot study these communities directly, by themselves and in partnership with our colleagues in neighboring countries. Joint research and plant protection projects are rare.
  
  
• In accordance with the principles of the "dominant species" school, which has prevailed in Bulgaria, past phytocenological studies did not lead to the development of a standard classification system, as did work in other phytocenological schools (e.g., the Braun-Blanquet school). Thus, our research results are not comparable with those in the countries of Central and Western Europe. Bulgarian experts are familiar with the main principles of the Braun-Blanquet school, but they are not acquainted with its research methods or classification system. Many of them are aware that training in this field is urgently needed to facilitate comparative research and analysis. Initial steps have been taken to overcome this problem, but a complete solution will require considerable money and time.
  
  
• Under the former totalitarian system, scientific experts were forced to observe complicated secrecy rules. This resulted in a series of restrictions that did not allow scientists to cite the exact geographic coordinates of any object, including natural territories! They were not allowed to publish accurate information about environmental pollution. Published maps were distorted. Many works could not be published in foreign journals and magazines. Contacts between Bulgarian scientists and colleagues in the west were restricted. As a result, Bulgarian experts could not take advantage of scientific advances in the west, while colleagues outside the country were unable to take advantage of work performed here.
  
  
• A detailed inventory of vegetation in a number of protected areas (primarily reserves) was prepared, but this valuable material was never published for lack of money. The work resulted only in an unpublished report to the Ministry of Environment. The authors' efforts to find sponsors have so far remained fruitless. Naturally they are discouraged and, lacking the means to publish their findings, they are unenthusiastic about conducting further research. This is especially regrettable in that some of the studied areas are biosphere reserves, and hence of global significance. Even more frustrating is the fact that publishing in Bulgaria, in comparison with other parts of the world, is quite inexpensive!
  
  
• Technical equipment in Bulgaria is indeed very poor and far behind modern standards. Land rovers are necessary for on-site work. The need for modern computers and software is also urgent.
  
  
• University curricula for biology students need to be revised to improve the quality and applicability of their special training. Opportunities and resources for young scientists to study in leading foreign institutes and laboratories are very limited.
  
  
• The opportunities for participation in international symposia, congresses, conferences, and seminars are also limited.
  
  
• Our specialized libraries receive few of the important scientific publications.

Areas in Need of Further Study

Information about the plant communities in the Rhodopes, the Pirin Mountain, the Predbalkan region, and the Tundzha plain is fragmentary (see Map 8). Parts of these regions (for example, the southern Pirins and the Dobrostanski massif of the Rhodopes) have been studied, but the results were never published. Information about some specific habitats - the riparian forests along the Kamchia River, sand-dune and coastal vegetation, fragments of steppe vegetation in northeastern Bulgaria, groups of rock vegetation in the central part of the Stara Planina Mountains and the southern Rhodopes, mesophytic meadow vegetation - is insufficient.

Taxonomic Richness

Bulgaria, despite its small territory, is characterized by a great variety of plant communities. More than one thousand types have been described so far. Most of these are forests; the rest are shrub, grass, and aquatic macrophyte communities. It is supposed that the variety of plant associations is much larger. (Appendix 1 presents 800 plant species which are dominant in the plant communities. They are essentially representative of diversity at the community or plant formation level.) Several factors account for this great degree of community diversity:

• Bioclimatic influences. Each of the various bioclimatic zones in Bulgaria - the mid-European, steppe, Black Sea, and Mediterranean) - is related to specific vegetational and floristic features. In some areas, two or more bioclimatic factors combine to create specific environmental conditions, lending additional nuance to plant community composition and structure.
  
  
• Orographic conditions. The diversity of plant communities is, to a great extent, attributable to the diverse orographic conditions. The mountainous nature of the Bulgarian landscape results in a considerable richness of environmental conditions and localized habitats.
  
  
• Glaciation. During the last glacial period, the highest mountains in Bulgaria - the Rilas and Pirins - were partially covered with ice. The Rhodopes, Strandzha, and central part of the Stara Planina Mountains were not glaciated. Thus, certain relict species and communities were preserved there.

Rare Communities

Unlike studies of flora and fauna, which are characterized by a clear concept of "rare" plant and animal species (as listed in the Red Data Book), phytocenology lacks clearly defined criteria for assigning plant communities to this category. Proposals to develop a "Green Book" of rare or threatened phytocenoses are not new, but realization of this goal lies in the distant future.

A "rare" category would most probably include the relict communities that are of special scientific interest, such as Fagus orientalis-Rododendron ponticum in the Strandzha region; Fagus sylvatica-Laurocerasus officinalis in the central part of the Stara Planina Mountains; Aesculus hyppocastanum on Preslavska Mountain; Pinus heldriechii in the Pirins and on Slavyanka Mountain; Castanea sativa in Belasitsa and the western part of the Stara Planina Mountains; Pinus peuce in the Pirins, Rilas, and the central part of the Stara Planina Mountains; Quercus coccifera in the valley of the Strouma River; Juniperus excelsa in the Kresna gorge and the central Rhodopes; Cercis siliquastrum on Preslavska Mountain; and Pinus nigra-Ostrya carpinifolia in the southern Rhodopes. The majority of these are confined to a few or even a single locality (Map 9).

There are some unique communities of Bulgarian endemics: Quercus protoroburoides in the Rila Mountains; Astragalus aitosensis in the eastern part of the Stara Planina Mountains; Astragalus thracica in the Tundzha plain and the eastern Rhodopes; Jurinea tzar-ferdinandii in the western and eastern parts of the Stara Planina Mountains and the eastern part of the Predbalkan region; Centranthus kellererii in the northern Pirins and Vrachanska Mountain; Festuca pirinensis in the Pirins; Festuca stojanovi in the western part of the Stara Planina Mountains and the western border mountains; Primula deorum in the Rila Mountains; Festuca balcanica in the central part of the Stara Planina Mountains and Vrachanska Mountain (Map 10). Equally significant are the plant communities where Balkan endemics are dominant (Map 11). (Appendix 2 contains a complete list of the communities where Bulgarian or Balkan endemics prevail).

There is no complete list of the various habitats of these communities, and no attempts have been made to classify them. Preparations for the participation of Bulgarian experts in the CORINE program will allow opportunities to use the classification system that has been adopted by the European Community member countries involved in the program. (See Habitats of the European Community in CORINE Biotopes Manual, Part 2, 1991). As research under the CORINE programme has not yet begun, here we shall try to adapt Bulgarian habitats to the European classification system only in the broader categories.

1. Coastal and halophytic communities

The Black Sea coast and open waters, and their hydrophytic vegetation.

11. Ocean and seas

11.1. Open marine waters
Pelagic biocenoses. Characterized by their planktonic communities and by the composition of their surface-feeding faunas (fish, sea mammals, and seabirds).

11.2. Seabed
Benthic communities of animals and algae occupying the sea floor in the infralittoral, circalittoral, and deeper zones.

11.3. Marine vascular vegetation
Beds of submerged marine vascular vegetation, except those of brackish seas (e.g., Zostera marina).

11.4. Brackish sea vascular vegetation

15. Salt marshes with halophytic vegetation
Found in the coastal zone and in some inland areas, consisting of typical halophytic communities such as Salicornia herbaceae. Their role in the structure of the vegetation cover is limited.

16. Coastal sand-dunes and sand beaches

16.1. Sand Beaches
These either lack vegetation or are covered by annual communities (e.g., Cakile maritima).

16.2. Dunes
These are covered by psammophytic vegetation, dominated by Leymus racemosus ssp. sabulosus, Ammophylla arenaria, Cionura erecta, Sylene thymifolia, etc.

18. Cliffs and rocky shores
Steep rocky shores adjacent to the sea. In addition to their botanical significance, they are often important nesting sites for sea birds.

2. Non-marine waters

22. Standing fresh water
Lakes, ponds, and pools of natural origin containing fresh (i.e., non-saline) water. Also man-made freshwater bodies.

22.4. Aquatic vegetation
Communities of Lemna, Spirodela, Wolfia, Utricularia, Potamogeton, Nymphaea, Nuphar, etc.

23. Standing brackish and salt water

24. Running water
All rivers and streams. Riverbank vegetation: Salix, Populus, Alnus, Typha, Phragmites.

3. Scrub and grassland

31. Heath and scrub

31.4. Alpine and boreal heaths
Dryas octopetalla, Bruckenthalia spiculifolia, Juniperus nana. Found in the alpine and subalpine zones of all high mountains.

31.5. Dwarf mountain pine (Pinus mugho) scrub
Forms zones in the Rila and Pirin Mountains. Separate groups can be found in the Stara Planina, Vitosha, and Rhodope Mountains.

31.6. Subalpine bush and tall herb communities
Juniperus sibirica, Alnus viridis, Salix herbacea, Vaccinium myrtillus, Vaccinium vitis-idaea, Rubus idaeus. Found in the sub-alpine zones of all high mountains. Their role in the structure of the vegetation cover is important. The occurrence of Chamaecytisus absinthyoides in the Rhodopes, Rilas, Pirins, and Slavyanka is more limited.

31.7. Hedgehog-heaths
Astragalus aitosensis.

31.8. Thickets
Medio-European rich-soil thickets: Prunus spinosa, Prunus mahaleb, Rosa spp., Cornus mas, Cornus sanguinea, Crataegus monogyna, Lonicera xylosteum, Rhamnus catarticus, Clematis vitalba, Ligustrum vulgare, Viburnum lantana, Viburnum opulus, Cotoneaster integerrimus, Coryllus avellana.

32. Sclerophyllous scrub
Found chiefly in the southern parts of the country on highly eroded calcareous terrains, mostly as secondary communities that have replaced former oak forests. Carpinus orientalis, Paliurus spina-christi, Syringa vulgaris, Cotynus coggyria, Quercus coccifera, Juniperus oxycedrus, Pistacia terrebinthus, Ozyris alba, Phyllerea latifolia.

35. Dry siliceous grasslands

35.2. Medio-European open siliceous grasslands
Open formations of dry, siliceous soils, often species-poor and with a strong representation of annuals (Aira capillaris, Nardurus lachenalii, Vulpia myuros, Filago arvensis, Trifolium arvense, Trifolium campestre). Perennials: Agrostis capillaris, Anthoxanthum odoratum.

36. Alpine and subalpine grasslands

36.1. Alpine formations of Carex curvula, Juncus trifidus, Agrostis rupestris.

36.2. Subalpine formations of Sesleria comosa, Festuca valida, Nardus stricta, Festuca nigrescens, Festuca poaeformis, Calamagrostis arundinaceae, Senecio nemorensis.

37. Humid grasslands
Deschampsia caespitosa, Juncus effusus, Juncus conglomeratus, Eryophorum latifolium, Eryophorum vaginatum.

38. Mesophile grasslands
Lowland and montane mesophile pastures and hay meadows.

38.1. Mesophile pastures
Lolium perenne, Cynodon dactylon, Poa annua, Agrostis capillaris.

38.2. Lowland hay meadows
Festuca pratensis, Poa pratensis, Cynosurus cristatus, Phleum pratense, Arenatherum elatius. 38.2. Lowland hay meadows Festuca pratensis, Poa pratensis, Cynosurus cristatus, Phleum pratense, Arenatherum elatius.

38.3. Xerophytic pastures
Dichantium ischaemum, Chrysopogon gryllus.

4. Forests

41. Broad-leaved deciduous forests

41.1. Beech forests

41.11. Central-European acidophilous beech forests with woodrush
Medio-European beech and, in higher mountains, beech-fir or beech-fir-spruce forests on acid soils, with Luzula luzuloides, Vaccinium myrtillus, Pteridium aquilinum. Found in the western and central parts of the Stara Planina, Sredna Gora, Rhodope, and western border mountains.

41.13. Neutrophilous beech forests
Medio-European and Atlantic forests, on neutral or near-neutral soils, with mild humus, characterized by a strong representation of species belonging to the ecological groups of Anemone nemorosa, Lamium galeobdolon, Galium odoratum, and Melica uniflora and, in the mountains, various Dentaria, forming a richer and more abundant herb layer than in 41.11.

41.16. Beech forests on limestone
They can be found in the southern parts of the country: the Rhodopes and southern Pirin Mountains.

41.17. Southern medio-European beech forests
Including Ostrya carpinifolia on calcareous rocky terrains and Laurocerasus officinalis in the central part of the Stara Planina Mountains.

41.19. Balkanic beech forests
Fagus moesiaca dominant. Found in the Predbalkan region to the Shoumen plateau to the north and along the border between the eastern and the central part of the Stara Planina Mountains.

41.191. Forests of Fagus orientalis
Can be found in the eastern part of the Balkan Mountains and in the Strandzha region. South-euxinic species are found in the undergrowth.

41.2. Oak-Hornbeam forests
Quercus petraea and Carpinus betulus dominant. Limited role in the structure of the vegetation cover. Found in the mesophile oak and hornbeam belts of most Bulgarian mountains.

41.3. Ash forests
Fraxinus excelsior dominant. Limited role in the structure of the vegetation cover.

41.7. Thermophilous and supra-mediterranean oak woods
Quercus pubescens dominant. Occupies the southern flanks with dry and shallow soils, mostly in the lower parts of the mountains.

41.8. Hop-hornbeam, oriental hornbeam, and mixed thermophilous forests

41.9. Chestnut woods
Can be found in the Berkovsitsa region of the Stara Planina Mountains and in Belasitsa.

41.A. Hornbeam woods
Limited occurrence in the mesophile oak and hornbeam belt.

41.D. Aspen woods
Limited occurrence in the beech belt.

41.H. Other deciduous woods
Most of Bulgarian oak forests belong here, as they have not been included in the CORINE classification.

41.H.1. Lowland forests of Quercus pedunculiflora
In the lowlands and plains in northeastern Bulgaria and the Thracian lowland. Once occupied rich moist soils, now almost entirely destroyed as a result of extensive clearing.

41.H.2. Xeromesophytic woods of Quercus cerris and Quercus frainetto
The two species form pure, monodominant communities, but are most often found in mixed forests. Important for the structure of the vegetation cover. Widely spread in the whole country. Secondary communities are predominant.

41.H.3. Forests dominated by Quercus virgiliana
Can be found mostly in northeastern Bulgaria and the Predbalkan region.

41.H.4. Quercus daleshampii forests
Widely spread, forming the mesophile oak belt in the mountains.

41.H.5. Quercus polycarpa forests
Can be found in the eastern part of the Stara Planina Mountains and on Strandzha.

41.H.6. Quercus protoroburoides forests
Occupy a specific niche above timber line in a single locality in the Rilas.

42. Coniferous woodland

42.1. Fir forests
Occupy the zone between the beech and the spruce forests, mostly on the northern mountain flanks, on rich, moist soil. Dominated by Abies alba.

42.1.B.6 Abies alba ssp. borissi-regis forests
Limited occurrence in the southernmost parts of the country: the southern Rhodopes, Slavyanka, Belasitsa.

42.2. Spruce forests
Conifer forests dominated by Picea abies. Important in the structure of coniferous forests. Cover extensive territories, mostly on the northern flanks of the higher mountains.

42.5. Scotch pine forests
Dominated by Pinus sylvestris. Cover extensive territories in the mountains, mostly in the Rhodopes. They can be found most often on the southern flanks on shallow, eroded soils.

42.6. Black pine forests
Dominated by Pinus nigra. Occupy mostly calcareous terrains in the southern parts of the country.

42.7. Pinus leucodermis forests
On calcareous terrains in the Pirins and Slavyanka.

42.73. Pinus peuce forests
Found on silicate terrains in the higher parts of the Rilas, Pirins, and the central part of the Stara Planina Mountains.

44. Alluvial and very wet forests and brush

44.1. Salix spp. brush or arborescent formations, along flowing water subject to periodic flooding.

44.3. Medio-European ash-alder woods
Alnus glutinosa formations on soils. Periodically inundated by the annual rise of the river level, but otherwise well-drained and aerated during low water.

44.B. Platanus orientalis forests
In river valleys in the southern part of the country.

5. Bogs and marshes

6. Inland rocks, screes and sands

6.1. On siliceous terrains
Mostly in the central part of the Stara Planina, Rila, and Pirin Mountains.

6.2. On calcareous terrains
In the Danubian plain; Rila, southern Pirin, and Slavyanka Mountains.

8. Agricultural land and artificial landscapes

Ecological Services

In principle, all plant communities provide services to other components of the natural ecosystems in which they are found. The communities of macrophytic aquatic plants around inland water basins have such specific functions for water birds. A number of plant communities provide seasonal shelter and food for migratory birds. More detailed information on this matter should be prepared with the cooperation of zoologists.

Fragility (high, medium, low)

Annual communities are the most fragile: Trachinia distachya, Psilurus incurvus, Vulpia myurus, Vulpia ciliata, etc. They are highly sensitive to climatic changes and especially to changes in temperature and soil moisture. In years with more favorable conditions they grow plentifully and form specific communities, mostly in areas where competition with other plants is less severe. In unfavorable climatic conditions they can remain dormant.

The medium fragility group includes several types of plant communities:

1. Riparian forests

They are directly dependent on the moisture regime. Even the smallest deviation upsets the forests' specific composition and structure. Unfortunately, such deviations now occur regularly due to the total xerophilization of the conditions as a result of anthropogenic activity. Specialists in this field are well familiar with this problem (for example, along the Kamchia River).

2. Psammophytic vegetation on sand dunes

Psammophytes occupy limited areas. They develop on a specific substratum outside of which they are unable to survive. They also fall within the zone of very high anthropogenic pressure. The construction of resorts and the active presence of countless tourists have serious impacts upon their natural composition. Recent research has shown that dune vegetation has been also been subject to unfavorable changes in natural successional processes as a result of progressive stabilization of the sand substratum.

3. Mesophile meadows

Communities dominated by Festuca pratensis, Poa pratensis, Poa sylvicola, Alopecurus pratensis and other mesophilic species. These species are good fodder plants, but in the last few decades the areas where they occur have been reduced. Biologically, mesophile meadows are highly sensitive to the regime of underground waters. Under conditions of insufficient moisture they change into xerophile pastures, which are usually dominated by Chrysopogon gryllus. When moisture is abundant, they often change into hygrophile acidic grass formations. The species with high fodder value are also vulnerable to grazing. When overtrampled, they are replaced by xerophile pasture species. In addition, fertilization creates conditions for ruderalization.

4. In principle, all communities that for various reasons occupy small areas and are fragmentary and unable to maintain their natural homeostasis belong to this group.

The third, lowest-fragility group includes some Mediterranean formations: Junipera excelsae, Querceta cocciferae, Phyllereeta mediae, and Pistacieta terrebintae. Bulgaria is the northernmost area of their occurrence, so they are relatively unstable.

Known Threats

We have no concrete data so far as regards the negative impact of certain problems of the global biosphere: the thinning of the ozone layer, the greenhouse effect, and desertification.

Unfavorable changes in the vegetation cover are related to direct and indirect forms of anthropogenic influence on a regional scale. As a result of human activity the conditions under which plants exist have deteriorated and plant communities have suffered considerable degradation. The first of these changes is the reduction in the area of forest communities, which in turn has resulted in a decrease in the biological and environment-forming role of the vegetation cover. Deforestation is particularly severe on the southern flank of the Stara Planina Mountains, in the eastern Rhodopes, at Ograzhden, in the southern Pirins, and in the lower mountain slopes of western Bulgaria. As a result, the upper timber line has been lowered in the Rila, Pirin, and the Stara Planina Mountains.

Over 70% of the Quercus cerris and Quercus frainetto forests consist of shoots and shrubs. Quercus daleshampii forests are severely affected by degradation processes. Castanea sativa forests are in poor condition. All these unfavorable changes are due to extensive cutting. The forest complexes in the oak belt, which fall in the highly urbanized zone, are in even worse condition.

Human beings have also caused widespread damage by converting forest communities into agricultural lands and pastures by eradicating, burning, and upturning them.

The mesophile meadows in valleys and plains are subject to extreme anthropogenic pressures. Over the last several decades they have suffered large-scale plowing and were destroyed over the greater part of their original area. Changes have taken place in their composition and their fodder value because of changes in the moisture regime, the use of fertilizers and pesticides, and grazing combined with haying. Few areas of mesophile meadow have been included in protected areas (mostly to protect the habitats of Leucojum aestivum).

River bed corrections and other hydromeliorative activities, including the ill-founded policy of draining water basins along the Danube and Maritsa Rivers and in other parts of the country, have led to the destruction of entire aquatic ecosystems, together with the macrophytic plant communities that were typical for them.

Construction of roads, powerlines, canals, rail-roads, houses, and industrial complexes has also resulted in the immediate destruction of natural communities.

Advanced degradational processes have taken place in highland pastures as a result of uncontrolled grazing. Over half of their area is occupied by Nardus stricta. The species composition from the point of view of fodder quality has also deteriorated. The presence of weeds and ruderal species has increased.

Data on the negative impact of industrial pollution is available in regions with large enterprises, including the oil-processing plant in Bourgas, the chemical works in Devnia, and the metallurgical plants in Kremikovtsi and Srednogorie. Information has been published about disturbances in the production process, the intensity of photosynthesis, and changes in the composition and structure of natural plant communities in these areas.

Sites Containing the Most Representative Sample of Bulgarian Biodiversity

1. The Pirin (especially the southern) Mountains
2. Rila Mountains
3. The central part of the Stara Planina Mountains
4. The western and central Rhodope Mountains
5. The valley of the Strouma River
6. Strandzha Mountain
7. The Black Sea region
8. Kabioushka Mogila (a hill near Shoumen)
9. The Preslav part of the Stara Planina Mountains
10. Belasitsa

Plant Communities of Proven or Potential Economic Importance

• For wood material and products: Quercus cerris, Quercus frainetto, Quercus daleshampii, Quercus polycarpa, Fagus sylvatica, Fagus sylvatica ssp. moesiaca, Fagus orientalis, Picea abies, Pinus sylvestris, Pinus nigra, Pinus peuce, Pinus heldreichii.
  
  
• As natural sources of fodder: meadow communities, dominated by Poa pratensis, Festuca pratensis, Poa sylvicola, and Alopecurus pratensis; pasture communities, dominated by Agrostis capillaris, Dichantium ischaemum, Chrysopogon gryllus, Festuca nigrescens, and Nardus stricta.
  
  
• For the needs of pharmaceutical industry: mesophile meadows with representation of Leucojum aestivum, Tilia spp. forests; Artemisia spp., Inula helenium, Ruta graveolens, Thymus spp., Cotynus coggygria, Urtica dioica, Matricaria chammomilla, and other communities.
  
  
• For the needs of food industry (in limited degree): Vaccinium myrtillus, Vaccinium vitis-idaea, Rubus idaeus, Prunus spinosa.

For the distribution of these communities, see Bondev's (1991) Map of Bulgaria's Vegetation (M=1:600,000).

Conservation Recommendations

Bulgaria has so far achieved good results in environmental protection. The network of protected natural areas includes the greater part of the plant communities that are of interest from the point of view of conservation. At the same time, these results are inadequate from the point of view of modern standards for environment optimization.

The biodiversity conservation strategy should determine the maximum desirable percentage of protected territories in the country's total area. The experience of the developed countries should be used, bearing in mind that Bulgaria has fortunately managed to preserve vast areas of natural complexes.

The existing network of protected areas is quite fragmented. There are too many small reserves like Amzovo, Patleina, and Momin Grad. The present state of the reserve network should be reassessed and smaller reserves of lesser significance should be placed in a lower category of protected areas.

When creating new reserves, the following requirements should be considered: they should be large enough to include buffer zones and should include not only the primary, best preserved plant communities, but also secondary ones, thus providing an opportunity for observation of natural regeneration processes.

It is vitally important that these areas be guarded properly. This is the most serious problem at present and almost invariably exists in all protected areas.

Bulgaria lacks experience in the management of national parks; this is a field in which foreign assistance will be required.

More active publicity and outreach work is needed to engage the population in environmental protection.

The concept of rational use of natural resources should be given priority among the leading concepts in the strategy. The strategy currently uses the term "natural resources" in its broadest sense, including biodiversity. This term should rather be used in a narrower sense, i.e. to refer to "economic resources". That would allow the creation of a clear concept of their rational use that corresponds to their production potential.

As regards the general approach to environmental protection, the theoretical principles of modern ecology should be applied. Knowledge of the structural and functional characteristics of natural ecosystems is essential for their proper conservation. We are deeply convinced that it is impossible to manage systems that have not been studied thoroughly.

From the point of view of ecology there are no valueless species. Every biological species is the result of millions of years of evolution and if natural selection has endowed it with the ability to exist, we must admit that it occupies a position of importance in the structural and functional organization of the ecosystems where it occurs. Even the smallest blade of grass, even a plain and minor insect, contribute to nature's integrity, just as the smallest components in a complicated timing mechanism are essential to its accurate functioning.

Appendix 1. List of Plant Communities predominated by Bulgarian endemic species

Distributed in Eastern Stara Planina Astragalus aitosensis - mixtoherbosa Astragalus aitosensis - Dichantium ischaemum Astragalus aitosensis - Festuca dalmatica Astragalus aitosensis - Alyssum tortuosum Astragalus aitosensis - Poa bulbosa	Distributed in Stara Planina Festuca stojanovi + Poa badensis Festuca stojanovi - Carex humilis Festuca stojanovi - Paeonia tenuifolia Festuca stojanovi - Poa bulbosa
Distributed in Slavyanka Convolvulus sundermanii - Festucopsis sancta	Distributed in Eastern and Western Rila Festuca riloensis + Carex curvula Festuca riloensis Festuca riloensis - Sesleria comosa
Distributed in Central and Vrachanska Stara Planina Festuca balcanica - Sesleria coerulea Festuca balcanica - Festuca poaeformis Festuca balcanica - Poa ursina Festuca balcanica Festuca balcanica - Achillea ageratifolia Festuca balcanica - Saxifraga rocheliana	Distributed in Chepan and in Eastern Stara Planina Jurinea tzar-ferdinandii - Helianthemum canum Jurinea tzar-ferdinandii - Bromus riparius
	Distributed in Pirin and Vrashanska Stara Planina Kentranthus kellererii
Distributed in Pirin (Orelyak) Festuca pirinensis - Sesleria coerulans Festuca pirinensis - Astragalus angustifolius Festuca pirinensis - mixtoherbosa	Distributed in Rila Mountains Primula deorum - Sphagnum sp div. Primula deorum - Scirpus caespitosus

Appendix 2. List of Plant Communities predominated by Balkan endemic species

Distributed in Slavyanka Mountains Abies alba ssp. borissi-regis + Pinus heldreichii Abies alba ssp. borissi-regis + Pinus heldreichii - Fagus sylvatica	Distributed in Southern Pirin and Slavyanka Mountains Festucopsis sancta Festucopsis sancta - Sesleria coerulans Festucopsis sancta - Stipa pulcheriana Festucopsis sancta - Sesleria rigida
Distributed in Preslavska Mountains Aesculus hippocastanum - Carpinus betulus Aesculus hippocastanum - Aegopodium podagraria Aesculus hippocastanum - mixtoherbosa	Distributed in Rila, Pirin, Vitosha and Stara Planina Festuca valida Festuca valida - Nardus stricta Festuca valida + Deschampsia caespitosa Festuca valida + Festuca paniculata Festuca valida - Sesleria comosa Festuca valida - Festuca poaeformis Festuca valida - Agrostis rupestris Festuca valida - Calamagrostis arundinacea Festuca valida - Veratrum lobelianum Festuca valida - Deschampsia flexuosa
Distributed in Pirin, Slavyanka and Rila Chamaecytisus absintioides - mixtoherbosa Chamaecytisus absintioides - Daphne oleoides
Distributed in Rila Mountain Festuca amethystina ssp. kummeri + Festuca poaeformis
Distributed in Vrachanska Mountain Festuca panciciana - Poa badensis Festuca panciciana - Satureja montana Festuca panciciana - Achillea clypeolata Festuca panciciana	Distributed in Rila and Pirin Mountains Genista rumelica Genista rumelica - mixtoherbosa Genista rumelica - Dichantium ischaemum Genista rumelica - Poa bulbosa Genista rumelica - Psilurus aristatus
Distributed in Pirin and Slavyanka Mountains Festuca penzesii + Sesleria coerulans Festuca penzesii - Festuca dalmatica Festuca penzesii - mixtoherbosa Festuca penzesii - Stipa pulcheriana Festuca penzesii - Astragalus angustifolius
	Distributed in Central Stara Planina and Rhodopes Haberlea rhodopaensis Pinus peuce - Fagus sylvatica Pinus peuce - Juniperus sibirica
Distributed in Besaparski hills Inula aschersoniana + Agropyron brandze + Koeleria glaucovirens Inula aschersoniana - Dichantium ischaemum - Asphodeline lutea Inula aschersoniana - Dichantium ischaemum - Teucrium polium Inula aschersoniana - Koeleria glaucovirens - Alyssum tortuosum Inula aschersoniana - Agropyron brandze - Helianthemum canum Inula aschersoniana	Distributed in Verenishko Bardo and Shiroka Mountains Ramonda serbica Ramonda serbica - Geranium macrorrhizum Ramonda serbica - Festuca dalmatica Ramonda serbica - Sesleria rigida Ramonda serbica - Dianthus petreus Ramonda serbica + Ceterach officinarum Ramonda serbica - Galium purpureum
	Distributed in Rila, Vitosha, Pirin Mountains Sesleria comosa - Festuca airoides Sesleria comosa - Carex curvula Sesleria comosa - Festuca riloensis Sesleria comosa - Carex laevis Sesleria comosa - Nardus stricta Sesleria comosa + Poa ursina - Campanula alpina Sesleria comosa - Avena scheuchzerii Sesleria comosa - Genista depressa Sesleria comosa
Distributed in Rila, Pirin, and Central Strara Planina Pinus peuce - Vaccinium myrtillus Pinus peuce - Vaccinium myrtillus - Luzula nemorosa Pinus peuce - Vaccinium myrtillus - Calamagrostis arundinacea Pinus peuce - Pteridium aquilinum Pinus peuce - Calamagrostis arundinacea Pinus peuce - Vaccinium vitis-idaea Pinus peuce + Picea abies - Vaccinium myrtillus Pinus peuce + Picea abies - Luzula nemorosa - Vaccinium myrtillus Pinus peuce + Pinus sylvestris - Vaccinium vitis - idaea Pinus peuce + Picea abies + Pinus sylvestris - Vaccinium myrtillus-Calamagrostis arundinacea Pinus peuce + Pinus heldreichii + Pinus sylvestris - Calamagrostis arundinacea
	Distributed in Central and Vrashanska Stara Planina Sesleria latifolia Sesleria latifolia - Festuca dalmatica Sesleria latifolia - Stipa joannis Sesleria latifolia - Satureja montana
	Distributed in Coastal Dunes Silene thymifolia - Medicago marina

Bibliography

Adamovic, L. 1909. "Vegetationsverhaltnisse der Balkan Lander (Molische Landes) Umfassend Serbien, Altserbien, Bulgarien, Ostrumelien, Nordthrakien und Nordmacedonien". In: Die Vegetation der Erde, XI, Leipzig: 1-567.

Alexandrov, A. 1983. "Preserving of Spruce Genetic Resources by the Archive Plantations and Provenance Trialis." (Bulgarian; Abstract in English.) III Nac. Conf. po Botanika (Third National Conference of Botany, Sofia, 1983) : 915-920. Publ. House of the Bulgarian Academy of Science.

Apostolova, I. 1987. "Minimal Area of Association Fagus sylvatica - Galium odoratum." (Bulgarian; Abstract in English), Ecologija. 20: 16-25.

Avramova, C. 1956. "Phytocoenological Investigations of Some Meadows in Sofia District". (Bulg. Abs. in German), Izvestija na Bot. Inst. BAN, (Bulletin of the Institute of Botany, Bulgarian Academy of Sci). 5: 191-227.

Bondev, I. 1959. Vegetation Cover of High - Mountain Region to Ridae Ibar in East Rila. (Bulg. Abs in German), Sofia. Publ. House of the Bulgarian Academy of Science.

Bondev, I. 1966. "High - Mountain Vegetation Cover of Bercovitsa and Chiprovska Mountain". (Bulgarian; Abstract in German). Izvestija na Bot. Inst., BAN, (Bulletin of the Institute of Botany, Bulgarian Academy of Science), 16:79-171.

Bondev, I. 1973a. "Climax and Secondary Vegetation in Bulgaria and its Mapping".(Bulg.) II Nac. Conf. po Botanika. (Second National Conference of Botany). Sofia: 183-189. Publ. House of the Bulgarian Academy of Science.

Bondev, I. 1973b. "Edificators and Dominants in the Vegetation Cover of Bulgaria".(Bulg.) II Nac. Conf. po Botanika (Proceedings of II National Conference of Botany, Sofia): 199-212. Publ. House of the Bulgarian Academy of Science.

Bondev, I. 1980. "Besonderheiten der Phlanzen Decke Bulgariens und Thre Erforschung." Folia Geobot. Phytotax. Praha. 15, 2: 189-190.

Bondev, I. and S. Ganchev. 1983. "The Situation and the Problems of Phytoecology in Bulgaria." (Bulg. Abs. in English). Sbornik III Nac. Conf. po Botanika (Proceedings III National Conference of Botany. Sofia 1981) : 23-34. Publ. House of the Bulgarian Academy of Science.

Bondev, I., S. Ganchev, and C. Kochev. 1964. "Subtype Halophyte Vegetation". In: Rastitelnost na livadite i pasishtata v Bulgaria (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I. Bondev, and S. Ganchev: 237-239, Publ. House of the Bulgarian Academy of Science.

Bondev, I. and J. Janev. 1983. "The Anthropogenic Factors Role for the Changes of the Natural Vegetation Around Tintiava Tourist House - Vitosha Mountain - Trends and Prognosis." (Bulg. Abs. in English). Sbornik III Nac. Conf. po Botanika (Proceedings III National Conference of Botany, Sofia, 1981) : 964-971. Publishing House of the Bulgarian Academy of Science.

Bondev, I., I. Lasarov, and M. Ljubenova. 1985. "The Vegetation of the Reserve "V. Kolarov" in the Rhodope Mountain". (Bulgarian; Abstract in English). Mejdunar. Symp. po Proect 8, MAB, Blagoevgrad (International Symposium Project 8 - MAB. Protection of Natural Areas and the Genetic Fund they Contain. 23-28.09.1985. Blagoevgrad), 2:133-141.

Bondev, I. and M. Ljubenov. 1983. "General Regularities in Distribution of Plant Associations in the Sofia Part of the Balkan Mountain." (Bulg. Abs. in English). Sbornik III Nac. Conf. po Botanika (Proceedings III National Conference of Botany, Sofia, 1981), :377-385. Publ. House of the Bulgarian Academy of Science.

Bondev, I. and M. Ljubenova. 1985a. "The Vegetation Cover of the Reserve "Chamlaka" in the Eastern Part of the Rhodopes." (Bulg. Abs. in English). Mejdunar. Symp. po Proect 8, MAB, Blagoevgrad (International Symposium Project 8 - MAB. Protection of Natural Areas and the Genetic Fund they Contain. 23-28.09.1985. Blagoevgrad), 2:104-113.

Bondev, I. and M. Ljubenova. 1985b. "Plant Communities in the Reserve Borovo in East Rhodopes Mountains". (Bulg. Abs. in English). Mejdunar. Symp. po Proect 8, MAB, Blagoevgrad (International Symposium Project 8 - MAB. Protection of Natural Areas and the Genetic Fund they Contain. 23-28.09.1985. Blagoevgrad), 2:142-147.

Bondev. I. and T. Meshinev. 1988. "Geobotany Mapping in the Mountain Regions of Bulgaria". (Russ.) Ecologija Vissokogorii. Publ. House Meznireba, Tbilissi, :104-108.

Bondev, I., T. Meshinev, N. Andreev, and L. Slavova. 1980 "The Flora in the Parangalitsa Reserve". (Bulgarian; Abstract in English). Regional. Symp. po Proekt 8, MAB (Regional Symposium under Project 8 - MAB. Conservation of Natural Areas and of the Genetic Material they Contain. 20-24 October 1980. Blagoevgrad) :110-111.

Bondev, I., T. Meshinev, and N. Andreev. 1983. "Botanical Characteristics of the Reserve "Bistrishko branishte"." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings III National Conference of Botany, Sofia, 1981), :935-948. Publ. House of the Bulgarian Academy of Science.

Bondev, I. and V. Nicolov. 1979. "Plant Cover in the River Iskar Gorge Between Plana and Lozenska Mountains." (Bulgarian; Abstract in English). Fitologija. 13 :3-30.

Bondev, I. and V. Velchev. 1947. "Anthropogenic influence on the Dynamic Processes in the Vegetation as a Component of the Natural Ecosystems in Bulgaria." (Bulgarian; Abstract in English) III Nac. Congress na Geografite v Bulgaria. (Third National Congress of Geographers in Bulgaria). :106-108.

Bondev, I. and V. Velchev. 1964. "Suggestions for Improvement of Meadows and Pastures." (Bulgarian; Abstract in English) In: Rastitelnost na livadite i pasishtata v Bulgaria (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I. Bondev and S. Ganchev. :251-257. Publ. House of the Bulgarian Academy of Science.

Bondev, I. and V. Velchev. 1984. "Ecological Structure of the Vegetation Cover in Bulgaria." (Bulgarian) Teoretichni i Prilojni aspecti na Rastitelnata ecologija (Theoretical and Applied Aspects of the Plant Ecology). Sofia, Part 1 : 77-84.

Bondev, I. and V. Velchev. 1986. "Anthropogenic Changes of the Natural Vegetation in the Strandzha-Sakar District and their Reflect on the Economic Significance."(Bulgarian) Sbornik Strandzha - Sakar, M. Tarnovo (Proceedings for District Strandzha-Sakar, Malko Tarnovo). Vol.2. Book 2 : 5-21.

Bondev, I., V. Velchev, and S. Ganchev. 1973. "Natural Vegetation of the Grey and Cinnamon Brown Forest Soils." II Nac. Conf. po Botanika (Second National Conference of Botany, Sofia). :126-130. Publ. House of the Bulgarian Academy of Science.

Bondev, I., V. Velchev, and S. Ganchev. 1982. "General Characteristics of the Contemporary Vegetation." (Bulg.) In: Geografija na Bulgaria. Fiz. Geogr. (Geography of Bulgaria. Physical Geography, Environment and Resources). :420-451. Publ. House of the Bulgarian Academy of Science.

Bondev, I., V. Velchev, S. Ganchev, and C. Kochev. 1969. "Draft for the Symbols of the 1:200000, Geobotanic Map of the People's Republic of Bulgaria." (Bulgarian; Abstract in English). Izvestija na Bot. Inst. BAN. (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 19 : 77-88.

Christov, M.A. 1944. "Composition of the Gitten Village Meadows." (Bulg.) Godishnik na Sof. Universitet, (Annual of the Sofia University, Faculty of Agriculture & Woods), XXII. 1943/44, Agriculture. I:85-105.

Christov, M.A. 1953. "Contribution to the Study of Our Natural Meadows in the District of Karlovo & Kazanluck." (Bulg.) Nauchni Trudove na Selskostop. Acad., Agronom. fac. (Study of the Academy of Agriculture. Faculty of Agriculture). I. 1952/53 :123-132.

Davidov, B. 1912. "Costal Sands in South Bulgaria and their Vegetation." (Bulg.) Sbornik na Prirodoizpitatelnoto Drujestvo (Proceedings of the Natural - Scientific Society). 5. Sofia.

Delipavlov, D. 1957. "Meadow Vegetation in the Village Ravnogor, District Peshtera." (Bulg.) Nauchni Trudove na Visshija Selscostop. Inst. (Scientific Proceedings of the Higher Agriculture and Stock - Breeding Institute) "V.Kolarov." Plovdiv. Book 4 : 249-268.

Dimitrov, D. and K. Kosev. 1987. "The Vegetation of the Danube Island Ljuljak." (Bulgarian; Abstract in English). Trudove IV Nac. Conf. po Botanika (Proceedings of IV National Conference of Botany, Sofia). III : 25- 31.

Dimitrov, S.G. 1952. "Meadow Vegetation in Smolijan - Chepelare Region". (Bulg.) Nauchni Trudove na Visshija Selskostop. Inst. "V.Kolarov", Plovdiv. (Scientific Proceedings of the Higher Agriculture and Stock - Breeding Institute) Book 1 :151-218.

Dingler, H. 1877. Das Rhodopengebirge und Seine Vegetation. Zeitschrift d.Deutsch. und Osfera. Verein. Bd. VIII.

Docheva-Popova, R. 1953. "Geobotanical Sletch with Fodder Characteristics of the Meadows and Pastures in the Territory of Village Chuprene (District Belogradchik)." (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 3:151-180.

Drajeva, L. 1963. "Hygrophytic and Mesohygrophytic Vegetation, Spread with the Stream of River Palacarija." (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 12:203-226.

Filipovitch, L. 1981. "Late Glacial Development of the Forest Vegetation in the High Mountain Part of Stara Planina." (Bulgarian; Abstract in English). Fitologija. 18:3-21.

Filipovitch, L. 1988. "Anthropogenic Influence on the Vegetation Development on the High Slopes of the Vitosha Mountain During the Late Postglacial Times." (Bulgarian; Abstract in English). Fitologija. 35:25-34.

Filipovitch, L. 1992. "Anthropogenic Activity as a Factor for the Formation of Contemporary Plant Communities in the Central Sredna Gora Mountain." (English). Fitologija. 43:30-34.

Ganchev, I. 1952. Vegetation Cover of the Eastern Part of Ljulin Mountain. (Bulg). Sofia. Publ. House of the Bulgarian Academy of Science.

Ganchev, I. 1958. "Peculiarities of the Vegetation of Ograjden Mountain, the Valley of Central Part of the Struma River and the Region Around the Town of Sandanski." (Bulg.) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 6:3-48.

Ganchev, I. 1961. Vegetation of the Lozenska Mountain and Peculiarities in It's Development. (Bulg.) Sofia. Publ. House of the Bulgarian Academy of Science.

Ganchev, I. 1962. "Forming and Development of the Herbaceous Communities in Bulgaria." (Bulg.) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 9:5- 42.

Ganchev, S. 1963. "Vegetation Cover of the Orophyte Belt in the West Part of the North-West Rila." (Bulg.; Sum in French). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 12:5-99.

Ganchev, I. 1964. "Economic Condition of Meadows and Pastures." (Bulg.) In: Rastitelnost na Livadite i Pasishtata v Bulgaria (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I. Bondev, and S. Ganchev. :240-245. Publ. House of the Bulgarian Academy of Science.

Ganchev, I. 1965. "Remain Forests in the Plain of Stara Zagora and on the Surrounding Hills." (Bulg.) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 14:19-87.

Ganchev, Sl. N. Iotzova-Baurenska, T. Meshinev, and M. Bojadzijsky. 1982. "The Influence of the Light Regime on the Growth of Potentilla fruticosa in Beglika Region - West Rhodopes." (Bulgarian; Abstract in English). Ecologija. 10:3-12.

Ganchev, S, and C. Kochev. 1962. "The Herbaceous Cover in the Valley of River Studena." (Bulgarian; Abstract in French). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 9:43-78.

Ganchev, S., C. Kochev, and D. Jordanov. 1971. "The Halophytic Vegetation in Bulgaria." (Bulgarian; Abstract in English). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 21:5-9.

Ganchev, I., N. Stojanoff, and T. Georgiev. 1955. "Notes on the Pasture Vegetation in Elena District." (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 4:61-94.

Georgiev, T. 1941. "Meadow Formations in Plana Mountain." (Bulgarian; Abstract in German). Godishnik na Sof. Univ. (Annual of Sofia University. Agronomy and Forestry Faculty). Book 19, 1-Agriculture :193-206.

Georgiev, T., and M. Christov. 1944. "Some Meadow Types in Our Country." (Bulgarian; Abstract in German). Godishnik na Sof. Univ. (Annual of Sofia University, Agronomy - Forestry Faculty). Book 22. 1- Agriculture :181- 317.

Gorunova, D. and H. Kochev. 1991a. "Vegetation Cover in the Basin of Chepelarska River (West Rhodopes). I." (Bulgarian; Abstract in English). Fitologija. 40:3-29.

Gorunova, D. and H. Kochev. 1991b. "Vegetation Cover in the Basin of Chepelarska River (West Rhodopes). II." (Bulgarian; Abstract in English). Fitologija. 41:3-27.

Gorunova, D. and H. Kochev. 1992. "Plant Cover in the Chepelarska River Basin (West Rhodopes). III." (Bulgarian; Abstract in English). Fitologija. 42:48-65.

Horvat, J., B. Pawlowski, und J. Walas. 1937. "Phytosoziologische Studien Uber die Hochgebirgsvegetation der Rila Planina in Bulgarien." Bull. de l'Acad. Polon. des Sciences Zetres. Ser. B.

Ivanow, B. und A.K. Drenowsky. 1910. "Uber die Pflanzenformationen der Alpinen Region des Witoschaberges in Bulgarien." Algemeine Botanische Zeitschrift. Karlsruhe i.B. 12:1-4.

Jordanov, D. 1931. "Phytogeographical Investigations of the Bogs in Bulgaria in Connection with Their Vascular Plants." Godishnik na Sof. Univ. (Annual of Sofia University. Faculty of Physics and Mathematics), 27, Book 3:75-156.

Jordanov, D. 1936. "About the Distribution of Steppe Vegetation in Bulgaria." (Bulgarian; Abstract in German). Sbornik na Bulgarian Academy na Naukite (Proceedings of the Bulgarian Academy of Science). XXXII:3-105.

Jordanov, D. 1938-1939. "Vegetation in the Bulgarian Part of Strandja Mountain." (Bulg.) Godishnik na Sof. Univ. (Annual of Sofia University. Faculty of Physics and Mathematics), 34-35, Book 3:409-476, 1-90.

Jordanov, D. 1944. "Vegetation of Sakar Mountain, Manastirsky, Svety Iliisky and Bakadjizite Hills." (Bulg.) Godishnik na Sof. Univ. (Annual of Sofia University. Faculty of Physics and Mathematics), 12, Book 3:268-399.

Jordanov, D., S. Ganchev, St. Denchev, T. Meshinev and N. Nicolov. 1972. "New Data About the Distribution and Ecological Peculiarities of Some Plant Species from the Western Part of Kazanlak Valley." (Bulg. Abs. in English). Izvestija. na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 22:135-142.

Jordanov, D. and C. Kochev. 1976. "Macrophytic Vegetation of Freshwater Basins Along Danube in Bulgaria, Dynamics under Anthropogenic Influence and Preservation." (Russ.) Bot. Zurnal (Botanical Journal), Leningrad. 61, 9:1294-1297.

Jurucova, L, and V. Velchev. 1987. "The Content of Heavy Metals in the Communities of Pinus peuce Griseb. in the Pirin Mountain." (Bulgarian; Abstract in English). IV Nac. Conf. po Botanika (Proceedings of IV National Conference of Botany, Sofia). III:148-155.

Jurucova, L, and V. Velchev. 1987. "The Content of Heavy Metals in the Communities of Pinus peuce Griseb. in the Pirin Mountain." (Bulgarian; Abstract in English). IV Nac. Conf. po Botanika (Proceedings of IV National Conference of Botany, Sofia). III:148-155.

Kitanov, B. 1984. "Phytogeographical and Phytocoenotic Characteristic of the Rhodopes Mountains." (Bulgarian; Abstract in English). Problemi na Geografijata (Problems of the Geography). 4:44-50.

Kochev, H. 1969. "Forest Vegetation at the Cherni Osam River (Central Balkan Mountain)." (Bulgarian) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 19:9-62.

Kochev, H. 1973. "Geobotanical and Phytoclimatic Investigations of Castanea sativa Forests in Bercovitca Region." (Bulgarian; Abstract in English). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 24:31- 73.

Kochev, H. 1976. Vegetation Cover of the Area between Rivers Batova and Dvoinytca, Varna Region. (Bulgarian) Publishing House of Bulgarian Academy of Science.

Kochev, H. 1983. "Ecological and Biological Groups of Plants in the Water-bodies Along the Black Sea Coast in Bulgaria." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981). :418-426.

Kochev, H. 1989. "Humid Areas in Bulgaria - Achievements and Perspectives of Phytological and Phytoecological Investigations." (Bulgarian; Abstract in English). Fitologija. 37:70-78.

Kochev, H., and G. Baeva. 1987. "Investigations on Chemical Composition of Some Plant Species in the Biosphere Reserve "Srebarna", Silistra District." (Bulgarian; Abstract in English). Trudove IV Nac. Conf. po Botanika (Proceedings of IV National Conference of Botany, Sofia). III:164-169.

Kocev, H., and L. Cerovska. 1987. "The Plant Coenosis in River-bed of the Beli Ossam River (Central Stara Planina Mountain)." (Bulgarian; Abstract in English). Trudove IV Nac. Conf. po Botanika (Proceedings of IV National Conference of Botany, Sofia). III:18- 24.

Kochev, H., and S. Ganchev. 1964. "Vegetation Cover of the Subalpine Part of Etropolska Stara Planina." (Bulgarian) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 13:81-7.

Kochev, H., S. Ganchev and D. Jordanov. 1971. "Chalophytic Vegetation in Bulgaria." (Bulgarian) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 21:5-50.

Kochev, H., S. Kovachev and J. Uzunov. 1983. "The Biological Characteristic of the Duranculak Lake and Some Problems of Its Protection." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981), :925-934.

Kochev, H. and J. Tzolova. 1987a. "Phytocoenological Investigations in the Bogs Reserve Persinsky Blata." (Bulg.) Teoretichni i Prilojni Aspekti na Rastitelnata Ecologija (Theoretical and Applied Aspects of the Plant Ecology). Sofia. Part 1:148- 156.

Kochev, H. and I. Tsolova. 1987b. "Ecological Investigation of the Protected Area "Lagat-Dramkata, Pleven District." (Bulgarian; Abstract in English). Trudove IV Nac. Conf. po Botanika (Proceedings of IV National Conference of Botany, Sofia). III:215-219.

Kostov, K. 1983. "Origin and Expansion of Oak Forests in Dry Plain of North Bulgaria." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981) :519-526.

Meshinev, T. 1973. "The Effect of Light on the Germination of Potentilla fruticosa Seeds." Dokladi na BAN (Compt. Rend. Bulgarian Academy Sci.). 26, 5:691-693.

Meshinev, T. 1975. "Germination of Potentilla fruticosa Seeds Under Natural and Experimental Conditions." In: V Chest na Akad. D. Jordanov (Honour of Acad. D.Jordanov). Publ. House of the Bulgarian Academy of Science :185-192.

Meshinev, T. 1985. "Phytocoenological Characteristics of the "Kastrakly Reservation." (Bulg.) Mejdunar. Symp. po Proekt 8 - MAB, Blagoevgrad. (International Symposium Project 8 - MAB, Protection of the Natural Areas and the Genetic Fund They Contain). 2:115-123.

Meshinev, T. 1990. The Grassland Vegetation in the Lowlands in Bulgaria. (Engl.) Lowland Grasslands of Eastern Europe. IUCN, Gland, Switzerland and Cambridge, UK.

Meshinev, T. and I. Apostolova. 1985. "Minimum Area of Piceetum myrtillosum Association in the "V.Kolarov" Reserve (West Rhodopes)." (Bulgarian; Abstract in English). Ecologija. 17:24-29.

Meshinev, T., D. Ivanov and Sl. Petrov. 1989. "Phytocoenological Role of the Mosses within Association Piceetum myrtillosum in the Region of the Vassil Kolarov Reserve (West Rhodopes.)" (Bulgarian; Abstract in English). Ecologija. 22:3-13.

Meshinev, T. and K. Katerova. 1983. "Ecological Estimation of the Protected Region Chernelka." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981) :957-963.

Meshinev, T., M. Mileva, G. Spiridonov, P. Vassilev, and R. Tekke. 1991. Sand Dune Inventory of Europe. Bulgaria. :71-73. (Engl.) Ed. DT. I. P. Doody. EUCC.

Meshinev, T. and O. Todorova. 1985. "Flora of the "Etara National Park." (Bulg.) Mejdunar. Symp. po Proekt 8 - MAB, Blagoevgrad. (International Symposium Project 8 - MAB, Protection of the Natural Areas and the Genetic Fund They Contain)., 3:27-32.

Meshinev, T, and P. Vassilev. 1983. "On the Problem about Key and Critical Parameters in Monitoring of the Environment." (Bulg., Abs. in English). Sbornik III Nac. Conf. po Botanika. (Proceedings of the III National Conference of Botany, Sofia, 1981) :972-979.

Meshinev, T., P. Vasilev, and A. Indgean. 1982. "Vegetation of the National Park Ropotamo." Nac. Teroet. Conf. "Sl. brijag" (Collection, National Theoretical Conference on Environmental Protection and Reproduction, 1-5.XI.1982. Slanchev Brijag) :94-98.

Nedeva, D. 1983. "Seasonal Dynamics of Meadow Vegetation in the District of the Town Bankja." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981) :449-456.

Nicolov, B. and S. Semenska. 1985. "Vegetation Relations in the Biosphere Reserve 'Koupena'." (Bulgarian; Abstract in French) Mejdunar. Symp. po Proekt 8 - MAB (International Symposium "Conservation of Natural Areas and of the Genetic Material they Contain - Project 8, MAB, 23-28.09.1985, Blagoevgrad), 1:97-102.

Nicolov, N., and V. Nicolov. 1984. "Biosphere Reserve "Chervenata Stena" - State of the Flora and Vegetation and Recommendation about Their Preservation." Ecological Cooperation (Bratislava) :40-43.

Penev, I. 1950. "Grass Composition of Pastures in West Stara Planina Mt. (Berkovski Balkan)." Sbornik na Opitnata Visokoplaninska Stancija (Collection of the High-Mountain Pasture Experimental Station), I:45-88.

Penev, I. 1953. "Herbaceous Cover of Some Pastures in the Rhodope Mts." (Bulg.) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 3:91-150.

Penev, I. 1960a. "Grass Communities on the Ridges of the Mechovershki & Parangalishki Divisions of Rila Mt." (Bulg.) Godishnik na Sof. Univ. (Annual of the Sofia University. Biological-Geological-Geographical Faculty). I. - Biology.

Penev, I. 1960b. "The Forest and Shrub Vegetation Along The Blagoevgrad's Bistritza River (Rila Mt.)." (Bulgarian) Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 7:107-163.

Penev, I. 1964. "Subtype Psychromesophyte High-Mountain Vegetation." (Bulg.), In: Rastitelnost na Livadite i Pasishtata v Bulgarija (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I.Bondev, and S.Ganchev. :130-161. Sofia. Publ. House of the Bulgarian Academy of Science.

Penev, I. 1965. "Grass Communities Above the Forest Zone of Vitosha Mt." (Bulgarian) Godishnik na Sof. Univ. (Annual of the Sofia University. Faculty of Biology), 58, Book 2, Botany. Microbiology, Physiology,& Biochemistry of Plants. 1963/1964. :59-94.

Penev, I. 1984. "Longos Forests at Bulgarian Black Sea Coast." (Bulgarian; Abstract in French). Godishnik na Sof. Univ. (Annual of Sofia University, Biological Faculty), Book 2, 74:113-129.

Petrov, P. and D. Stojanov. 1983. "Inventory of the Forest Plant Resources as a Source of Food and Medicinal Stuffs." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981) :537- 544.

Russakova-Anastassova, V. 1986. "A Map of the Present Alpine and Subalpine Vegetation in the Rila Mountain." (Bulgarian; Abstract in English). Fitologija. 31:34-51.

Russakova-Anastassova, V. 1987. "Problems of Mapping of the Vegetation in Bulgaria." (Bulgarian; Abstract in English). Trudove IV Nac. Conf. po Botanika (Proceedings of IV National Conference of Botany, Sofia) III:10- 17.

Simeonovski, M. 1965. "The Vegetation of the Calcareous Habitats of Rila Mt." (Bulg.) Godishnik na Sof. Univ. (Annual of the Sofia University), 58. II.

Simeonovski, M. 1967. "Grass Communities in the Marinkovitza Region."(Bulg.) Godishnik na Sof. Univ (Annual of the Sofia University). 60.II.

Stanev, St. 1977. "Geobotanical Characteristics of Several Plant Communities, Specific for the Bessaparski Hills." I (Bulg. Abs. in English), Fitologija. 6:16-32.

Stanev, St. 1977. "Geobotanical Characteristics of Several Plant Communities, Specific for the Bessaparski Hills." II (Bulg. Abs. in English), Fitologija. 7:25-50.

Stanev, St. 1986. "Tree and Shrub Vegetation of the Besaparsky Ridove Hills." (Bulg. Abs. in English), Fitologija. 32:16-69.

Stefanoff, B. 1923. "Wood Formation in North Strandzha." Godishnik na Sof. Univ (Annual of the Sofia University, Faculty of Agriculture.). II:33-68.

Stefanoff, B. 1927. Origin and Development of Vegetational Types in the Rhodope Mts. State Publisher's, Sofia.

Stefanoff, B. 1950. "State and Biological Peculiarities of the Forest Vegetation in Bulgaria." (Bulg. Abs. in German), Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 1:30-191.

Stoyanoff, D., E. Pavlova, M. Rangelova, I. Bondev, T. Meshinev, N. Andreev, and L. Slavova. 1978. "Methods of Complex Investigations in the Reserves and Other Protected Areas." Proceedings of the Committee of Environment. Sofia, 1:4-23.

Stoyanoff, I. 1947. "Contribution to the Study of the Composition of the Mountain & High Mountain Pastures & Meadows in West Bulgaria." (Bulg.) Godishnik na Sof. Univ. (Annual of the Sofia University, Agronomy and Forestry Faculty). XXV. 2:115-118.

Stoyanoff, I. 1948. "Contribution of the High-mountain Pastures in the West Rhodope Mt." (Bulg.). Godishnik na Sof. Univ. (Annual of the Sofia University, Forestry and Technical Faculty). 1:321-335.

Stoyanoff, N. 1922. "On the Vegetation of the Ali Botush Mt." (Bulg.) Godishnik na Sof. Univ. (Annual of the Sofia University, Faculty of Physics and Math.), XVII:1-35.

Stoynoff, N. 1926. "On the Origin of the Xerotermic Plant Element in Bulgaria." Journal of Ecology. XIV. 1:138-154.

Stoyanoff, N. 1926. "Uber die Verbreitung der Orientalischen Buche auf der Balkanhalbinsel." Magyar Botanikay Lapokev, 1-12:131-136.

Stoyanoff, N. 1927. "Contribution to the Study of Woods in the East Balkan Mt." (Bulg. Abs. in German). Godishnik na Sof. Univ. (Annual of the Sofia University. Faculty of Agriculture), V:345-394.

Stoyanoff, N. 1928. "Longos Forest Along River Kamchia and the Longos Forests as a Plant Formation." (Bulg.) Gorskostopanski Pregled (Forest Review), 14, 8-9:341-354; 10:148-149.

Stoyanoff, N. 1929. "Der Longos-Wald in Bulgarien." In: Botanische Jahrbucher fur Systematik, Pflanzengeschichte und Pflanzengeographie. Bd. LXII. 5:502-523.

Stoyanoff, N. 1929. "Ergebnisse Eines Fruhlingsausfluges in Bulgarisch - Macedonien." Izvestija na Bulg. Bot. Drujestvo (Bulletin of the Bulgarian Botanical Society). III:57-64.

Stoyanoff, N. 1932. "The Beech Woods of the Balkan Peninsula" In: Die Buchenwalder Europas. Veroff. d. Geobotan. Inst. Rubel, Zurich. 8:182-218.

Stoyanoff, N. 1934. "Vegetational Relations in the Sofia Valley. I." (Bulg. Abs. in German). Godishnik na Sof. Univ. (Annual of the Sofia University). XII:750-784.

Stoyanoff, N. 1935. "Vegetational Relations in the Sofia Valley. II." (Bulg. Abs. in German). Godishnik na Sof. Univ. (Annual of the Sofia University). XIII:238-278.

Stoyanoff, N. 1936. "Characteristique Phytogeographique du Massiv de Rila-Rhodopes et de Pirin." In: Resumes des Communications Presentees a la III-e Section (Phytogeographie) du IV-e Congres des Geographes et Ethnographes Slaves a Sofia. :9-11.

Stoyanoff, N. 1937. "Vegetational Relations in the Sofia Valley. III." (Bulg. Abs. in German). Godishnik na Sof. Univ. (Annual of the Sofia University). XV:1-40.

Stoyanoff, N. 1938. "Flora on the Bistrishki Reservation." (Bulg. Abs. in German). Sbornik na Prirodozashtitnoto Drujestvo (Union for Native Environmental Protection Collection). II:13-46.

Stoyanoff, N. 1941. "An Attempt in Characteristic of the Main Phytocenoses in Bulgaria." (Bulg. Abs. in German). Godishnik na Sof. Univ. (Annual of the Sofia University. Faculty of Physics and Mathematics.) XXXVII, Natural History, III:93-194.

Stoyanoff, N. 1947a. "Grass Vegetation on the Belenski Island. I." (Bulg.) Gorsko stopanstvo (Economy Forestry) III. Book 1-2:21-28.

Stoyanoff, N. 1947b. "Grass Vegetation on the Belenski Island. II." (Bulg.) Gorsko stopanstvo (Economy Forestry). III. Book 3-4:39-46.

Stoyanoff, N. 1947c. "Grass Vegetation on the Belenski Island. III." Gorsko stopanstvo (Economy Forestry). III. Book 5-6:166-173.

Stoyanoff, N. 1948. The Vegetation of the Danube Islands Near Bulgaria and It's Utilization. (Bulgarian; Abstract in German). Sofia, Publishing House of the BAS.

Stoyanoff, N. 1964. "Origin of Meadows and Pastures." In: Rastitelnost na Livadite i Pasishtata v Bulgarija (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I. Bondev, and S. Ganchev. :246- 250. Publ. House of the Bulgarian Academy of Science.

Stoyanoff, N. and B. Achtarov. 1951. "Ephemeroid Plant Communities in Our Southern Regions." (Bulg. Abs. in English). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science), 2:48-72.

Stoyanoff, N. and B. Achtarov. 1953. "Flora of the Golo Bardo Mt. in West Bulgaria." (Bulg. Abs. in English). Doklady BAN (Compt. Rend. Bul. Acad. Sci.). IV:21-24.

Stoyanoff, N., G. Georgiev, and I. Ganchev. 1955. "Notes on the Pasture Vegetation in Elena District."(Bulg. Abs. in English). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 4:61-94.

Stoyanoff, N., B. Kitanov, and V. Velchev. 1955. "Geobotanical Works in South Dobrudzha."(Bulg.) In: Sbornik na Expediziata po Polezashtitnite Pojasy ot 1952 (Collection of the Expedition for the Field Protection Zones from 1952.) Bulgarian Academy of Science :59-125.

Stoyanoff, N., and B. Stefanoff. 1922. "Phytogeografical and Floristic Characterization of Pirin Mt." (Bulg. Abs. in German). Godishnik na Sof. Univ. (Annual of the Sofia University, Faculty of Physics and Math), XVIII:1-27.

Stranski, Iv. 1921. "Vegetational Relations in the Middle Rhodope Mts." Sbornik na BAN (Bulgarian Academy of Science Collection). :1-141.

Turrill, W.B. 1929. The Plant Live of the Balkan Peninsula. Oxford:1-140.

Valev, S. 1953. "The Natural Vegetation and Vegetational in the Valley of Botevgrad." Godishnik na Sof. Univ. ( Annual of Sofia University. Biological Faculty). Book 1, 47:83-129.

Valev, S. 1955. "Some Features of the Vegetation in the Part of Rjana Mountain."(Bulg. Abs. in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 4:185-238.

Valev, S. 1961. "Meadow and Pasture Vegetation in the Valley of Ichtiman." (Bulg. Abs. in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 8:69-87.

Valev, S. 1964. "Subtype Hydrophyl Eutropic Vegetation (Swampy Meadows)" (Bulg.). In: Rastitelnost na livadite i pasishtata v Bulgaria (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I. Bondev, and S. Ganchev :24-28. Publ. House of the Bulgarian Academy of Science.

Valev, S., N. Stojanoff, B. Kitanov, B. Achtarov, and I. Ganchev. 1964. "Subtype Mesophyte Grass Vegetation." In: Rastitelnost na livadite i pasishtata v Bulgaria (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I. Bondev, and S. Ganchev. : 29-129. Publ. House of the Bulgarian Academy of Science.

Vassilev, P. 1980. "Vegetational Cover of the Golo Bardo at the Town of Pernik." (Bulg.) Probl. na Obuch. po Opasv. na Ocolnata sreda (Problems of the Education about Protection of the Environment.), Sofia :53- 62.

Velchev, V. 1958. "Geobotanical Notes Upon the Meadows and Pasture Vegetation in Troyan and Teteven Districts." (Bulg. Abs. in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 6:49-77.

Velchev, V. 1962. The Herbaceous Cover of Calcareous Terrains in the Region Dragoman-Beledie-Han, District of Sofia. Sofia. Publ. House of the Bulgarian Academy of Science.

Velchev, V. 1970. "Convolvulus compactus Boiss. in Bulgaria." (Bulgarian; Abstract in English). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 20:115-122.

Velchev, V. 1971. The Vegetational Cover of Vratsa Mountain. Sofia. Publ. House of the Bulgarian Academy of Science.

Velchev, V. 1973. "Phytocoenological Investigation of the Pinus peuce Griseb. in Central Balkan Range." (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 24:169-198.

Velchev, V. 1983."Development and Achievements of the Botanic Science in Bulgaria After the Second National Conference and its Problems in the Five-year Plan and Till 1990." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981), :9-22.

Velchev, V. and B. Achtarov. 1964. "Subtype Ephemeral-like and Ephemeral Vegetation." In: Rastitelnost na livadite i pasishtata v Bulgaria (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I.Bondev, and S. Ganchev. :219-236. Publ. House of the Bulgarian Academy of Science.

Velchev, V., B. Achtarov, and S. Valev. 1964. "Subtype Xerophyte Grass Vegetation." In: Rastitelnost na livadite i pasishtata v Bulgaria (Vegetation of Meadows and Pastures in Bulgaria). Edited by I. Ganchev, I. Bondev, and S. Ganchev :162-218. Publ. House of the Bulgarian Academy of Science.

Velchev, V. and I.Bondev. 1975. "Spreading, Ecological and Biological Peculiarities and Phytocoenological Characteristics of Astragalus aitosensis Ivanisch." (Bulgarian; Abstract in German). In: V Chest na Acad. D. Jordanov (Honour of Academician Daki Jordanov). Sofia. Publ. House of the Bulgarian Academy of Science :121- 159.

Velchev, V. and I. Bondev. 1982. "Psammophytic Vegetation in Our Country and Problems of its Conservation." (Bulgarian), Nac. Teoret. Konf. "Sl. Brijag", (National Theoretical Conference about Protection of the Environment. 1-5.11.1982. Sunny Beach). 1:298-301.

Velchev, V. and I. Bondev. 1984. "Ecological Peculiarities and Position of Phillyrea latifolia L. in the Vegetation Cover of Bulgaria. (Bulgarian; Abstract in English). Savremenni Teoret. i Prilojni Aspecti na Rast. Ecologija (Modern Theoretical and Applied Aspects of the Plant Ecology). Sofia. 1:106-116.

Velchev, V, and I. Bondev. 1984. "Threaten and Rare Plant Communities in Bulgaria."(Bulgarian; Abstract in English). Savremenni Teoret. i Prilojni Aspecti na Rast. Ecologija (Modern Theoretical and Applied Aspects of the Plant Ecology). Sofia. 1:94-105.

Velchev, V., I. Ganchev, S. Denchev, and B. Djancov. 1968. "Contribution about Investigation the Composition and Plant Geographic Peculiarities in Sashtinsca and Ichtimanska Sredna Gora." (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 18:93-99.

Velchev, V., S. Ganchev, T. Meshinev, and P. Vassilev. 1983. "Programme of Complex Ecological Investigations at the Experimental Base "Beglica" - West Rhodope Mountains." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981) :359- 366.

Velchev, V., S. Ganchev and P. Vassilev. 1975. "Ecological and Biological Studies on Ramonda serbica Panc. and Haberlea rhodopensis Friv." (Bulgarian; Abstract in English). In: V Chest na Akad. D.Jordanov (Honour of Academician Daki Jordanov). Sofia. Publ. House of the Bulgarian Academy of Science :175-184.

Velchev, V., D. Jordanov, and S. Ganchev. 1965. "Investigation of Acer monspesulanum L. in Nord-West Bulgaria." (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 15:91-117.

Velchev, V., D. Jordanov, and S. Ganchev. 1973. "Investigation of Ramonda serbica Panc. in Bulgaria. (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 24:139-167.

Velchev, V., T. Meshinev, P. Vassilev, and I. Apostolova. 1987. "Biological Productivity and Phytocenotic Role of the Grass Components in Association Piceetum myrtilosum - West Rhodopes." (Bulg., Abs. in English). Trudove IV Nac. Konf. po Botanica. (Proceedings of the IV National Conference of Botany, Sofia), III:45-52.

Velchev, V., D. Peev, and P. Vassilev. 1985. "State and Problems of the Preservation of Threatened and Role Plants and Plant Communities in Strandzha - Sakar Region." (Bulgarian; Abstract in English.) Ecologija, 17:10- 23.

Velchev, V. and P. Vassilev. 1970. "A Phytocoenological Study of Kentranthus kellereri Stoj. et Stef. in the Northern Part of the Pirin Mountain Range." (Bulgarian; Abstract in English). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 20:123-130.

Velchev, V. and P. Vassilev. 1971. "One Plant Community of Astragalus angustifolius Lam. in Kotel - Varbitsa Part of the Eastern Balkan Range." (Bulgarian; Abstract in German). Izvestija na Bot. Inst. BAN (Bulletin of the Institute of Botany, Bulgarian Academy of Science). 21:77-80.

Velchev, V. and P. Vassilev. 1975. "Ecological and Biological Investigation of Festuca pungens Kit. during Germination. (Bulgarian; Abstract in German). Ecologija. 1:5-7

Velchev, V. and P. Vassilev. 1976. "Ecological, Biological and Phytocoenological Study of the Seaside Pancratium Lily (Pancratium maritimum L.) in the Sozopol Region." (Bulg. Abs in English). Fitologija. 5:3-20.

Velchev, V. and P. Vassilev. 1982. "Quercus coccifera L. in Bulgaria and Its Protection." (Bulg.) Nac. Teoret. Konf. "Sl. Brijag" (National Theoretical Conference about Protection and Reproduction of the Environment. 1-5.11.1982. Sunny Beach). 1:302- 305.

Velchev, V., and P. Vassilev. 1983. "Endemic Plant Communities in Bulgarian Mountains and Status of the Protection." (Bulgarian; Abstract in English). Mejdunar. Simp. po Proect 6, MAB (International Symposium Project 6 - MAB. Interrelations Man - Mountain Ecosystem. 24-29.10.1983. Vratza). 1:84-90.

Velchev, V., and P. Vassilev. 1984. "Ecological and Phytological Role of Astragalus angustifolius Lam. in the Vegetation of Bulgaria." (Bulgarian; Abstract in English). Savremenni Teoret. i Prilojni Aspecti na Rast. Ecologija (Modern Theoretical and Applied Aspects of the Plant Ecology). Sofia. 1:125-131.

Velchev, V., P. Vassilev, and A. Indjeian. 1985. "Vegetation of the Reservation "Boraka" in the Eastern Part of the Rhodope Mountains." (Bulgarian; Abstract in English). Mejdunar. Symp. po Proect 8, MAB, Blagoevgrad (International Symposium Project 8 - MAB. Protection of Natural Areas and the Genetic Fund they Contain. 23-28.09.1985. Blagoevgrad), I:104-113.

Velchev, V., P. Vassilev, and T. Meshinev. 1979. "The Influence of the Environment on the Generative Reproduction of Pancratium maritimum." (Bulgarian; Abstract in English). Ecologija. 5:64-71.

Velchev, V., P. Vassilev, and T. Meshinev. 1983. "Vegetation of the Reserve Silkossia." (Bulgarian; Abstract in English). Sbornik III Nac. Conf. po Botanika (Proceedings of the Third National Conference of Botany, Sofia, 1981) :949-956.

Velchev, V., P. Vasilev, and T. Meshinev. 1989. "Ecological Investigations in the Institute of Botany with Botanical Garden at the Bulgarian Academy of Sciences - Achievements and Aims." (Bulgarian; Abstract in English). Fitologija, 37:35-45.

Velchev, V., P. Vassilev, T. Meshinev, and A. Ingejan. 1984. "Ecological Requirements and Participation of Juniperus excelsa M.B. in the Vegetational Cover of Bulgaria." (Bulgarian; Abstract in English). Savremenni Teoret. i Prilojni Aspecti na Savr. Ecologija (Modern Theoretical and Applied Aspects of the Plant Ecology). Sofia. 1:132-139.

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