Euro-Siberian region is represented by Euxine province in. Turkey. This region ..... Lake extends to Karaman, NiÄde, Sivas and Ãankırı with some interruptions.
AVCI, M. (1996). "The floristic regions of Turkey and a geographical approach for Anatolian diagonal", Review of the Department of Geography, University of Istanbul, Number 3, 59-91.
THE FLORISTIC REGIONS OF TURKEY AND A GEOGRAPHICAL APPROACH FOR ANATOLIAN DIAGONAL
Meral AVCI*
Turkey has a variety of plant species due to her position on the earth and to the characteristics of her climate, soil and geomorphology. This variety in plant species projects on the plant communities formed by clustering of plants having similar appearances and living conditions, although they are of the same species or of a different one. A really mozaic appearance occurs in the country in general, in terms of the geographical distribution of the vegetation cover accompanied by the local conditions. Turkey is one of the richest locations of the world regarding the plant species distributed on her. While, in the 1950s, it was known that 2480 plant species were found in Turkey (BİRAND, 1952), this number currently exceeded 10.000 with the addition of subspecies and varieties. This figüre is too high to be compared with the plant species in the countries of Northern Africa, Europe and in a larger part of Asia. Moreover, the number of taxon in Turkish flora (ali of the steps in the plant systematics such as family, genus, species, subspecies and variety) is closer to the number of taxon in ali Europe (GEMİCİ et al., 1992 : 64). The units of floristic domain which appear by the distribution of plant species and families bearing a resemblance to each other in terms of origin in certain areas of the earth are classified by various criteria). In this classification, the largest floristic units * Dr. Meral Avcı, is a research assistant in Geographical Department of the University of İstanbul.
60 of the world from «Floral Kingdoms». Within these large kingdoms, one distinguishes «Floral Regions» (ERİNÇ, 1977: 112). While the boundaries of floristic locations of various sizes are being drawn, other basic criteria are considered, such as differences betvveen regions, vegetation, floral history and the rate of endemics, besides the areas of the families. Since Humboldt, bio-geographists and botanists tried to separate the world into natural chorologic units or floral areas (phytochoria). Humboldt tried to classify the plants which dominated the geographical landscape according to their external appearances or, in other words, to their physionomies, but at the same time, he considered the relationship of the plants to their habitat. Humboldt's ecological and physionomical classification was later altered by other workers. In 1823, Shchouw described the units of plant geography based on endemic and floristic autonomy. In 1855, Candolle accepted not only the existence of the regions of plant geography, but he also distinguished the historical and actual zones (ARDEL, 1960 : 114; ZOHARY, 1973 : 77; USLU, 1983 : 35). One of the important works which clarified the distinction of floral regions was Grisebach's «Vegetation der Erde» published in 1884. Grisebach distinguished the regions known today as phytogeographical regions, adapting them to the natural units of the earth. A significant part of the boundaries drawn for these regions by Grisebach, who knew most of them well, were adopted later by plant geographists (ZOHARY, 1973 : 77). Grisebach who distinguished 5 floral regions on the earth such as Arctic, Forest regions of the Eastern Hemisphere, Mediterranean, Steppe and ChineseJapanese floral regions, included Turkey into two different floral regions according to the data known then (Figüre 1). On the map of Grisebach's vegetation regions, the whole of Trakya (Thrace), coastal regions of Black Sea, Aegean and Mediterranean were included in the Mediterranean Region, and the remaining inner areas of Turkey were included in the Steppe Region (GRİSEBACH, 1884). Good, in order to describe the total vegetation of the world based on a floristic classification, considered Grisebach's work, who tried this distinction for the first time. The book «Plant
62 Geography» of Good, published in 1955, emphasized not only the fundamental knowledge of the subject, but also the scope of the concept, «Phytogeographical Regions» (ZOHARY, 1973 : 77). According to Zohary, Engler's approach to the region concept is mainly floristic. Engler who did not accord much importance to ecology and vegetation depended clearly on «floristic indices» for the phytogeography units of the past and present. While his classification of «Floristic Kingdoms» was based on the past floral units, the essential consideration in «Floral Regions was physionomy of vegetation (ZOHARY, 1973 : 77). Zohary pointed out that, the book «Vegetationgebiete» written by Drude in 1890, did not bring new points of view to the subject (ZOHARY, 1973 : 77). However, Drude, in the French translation of his book, published in 1897, accepted that the plant geography had been a branch of plıysical geography. Drude emphasized that he gave due consideration to botanical events and contended with the general lines of the systematic floristic, and, on the other hand, he considered the part of most of the geographical events quite large. Drude describes the concept of «Floral Region» as follows : «Floral Regions are areas where some families containing certain special genera are included mostly». Drude's Floral Regions which were classified into three groups such as Boreal (belonging to the North), Austral (belonging to the Tropics and the South), and Oceanic included, according to the essentials in the Grisebach's classification, 21 areas and different vegetation regions in these areas (İNANDIK, 1969 : 11-13). Diels who, among others, made the first floristic classification in the world considered floristic plant geography as the manner of plants to acquire areas, the border of these areas, the factors influencing them, their occurrence and their being continuous or patchy. According to him, the areas which were the bases of floristic plant geography (which could be represented only by the recognition and comparison of species collected from these places) explained, at the same time, the systematic formation of the flora and made the classification of the world into plant regions possible. Diels, emphasizing that, in the classification of floral regions, floristic relations which occurred as a result of developments during
63 geologic periods and ecological plant geography should be considered together, distinguished six floral regions such as Holarctis, Paleotropis, Neotropis, Australis, Capensis, and Antarctis, and included Turkey as a whole in the Holarctis floral regions (DIELS, 1908 and Figüre 2). However, Gaussen included Turkey into Mediterranean floral region which encompassed a rather large area in the southern part of Holarctic floral region and which was one of the 8 floral regions he distinguished for the world (Figüre 3). Gaussen, who also separated Mediterranean floral regions into 15 small divisions, suggested that these divisions were formed as a result of changes occurring from place to place in the characteristics of climate, soil, and geomorphology, and differences in plant communities depending on these changes (GAUSSEN, 1933 : 178, 183-185). According to Walter, in a classification regarding floral regions, the essential concern of the subject has to be the past conditions of the plant together with their actual distribution. The actual distribution which can be explained by considering past characteristics, genetic and ecological conditions, can be studied only by distinguishing floral regions and areas (İNANDIK, 1969 : 19-20 referring to WALTER 1954). Currently, the classification of Turkey's floral regions has been clarified in the light of new researches. Among these studies, those of Davis and Zohary deserve attention (DAVİS, 1965 and 1971; ZOHARY, 1971 and 1973). Davis considered present flora and vegetation rather than climax vegetation of the past in the classification of floral regions. Zohary, on the other hand, determined floral regions not only according to the floral and vegetational inventory but also on the basis of past flora, that is, floral history. According to Zohary, trees are the most reliable indices of the vegetational history. The trees which are preserved in cemeteries and woods in steppe areas may be of use in the determination of the climax community of these areas. These are of crucial importance regarding the relations which are present between the current vegetation and the past one (ZOHARY, 1971 : 43-51).
Review F. 5
66 Apart from these considerations of Zohary about the classification of floral zones, Davis suggested that floral zones (phytochorion) were essentially a floristic concept, and that it would make sense to classify them not by remains scattered över the region, but by floral composition of present day. Moreover, according to Davis who suggested that most of the trees had no value as the indices of today's phytogeography regions, some species such as Juniperus excelsa, Pinus nigra, Quercus pubescens, Q. cerris and Pistacia atlantica were in their native habitat in two even three phytogeographical regions (DAVİS, 1971 : 15; ZOHARY, 1971 : 50) (Figüre 4). There are 3 floral regions in Turkey, although the boundaries change according to the criteria essentially used : 1. Euro -Siberian region 2. Mediterranean region 3. Irano -Turanian region 1. Euro -Siberian Region : This floristic region is divided into two areas as Euxine province and Hyrcanian province. The western area close to the Black Sea is called Euxine province, and the eastern one dominating northern Iran and Talysch regions is termed Hyrcanian province. Although these two areas separated by the Caucasian mountains from each other have significant similarities, they are markedly different as to their floristic compositions. Euro-Siberian region is represented by Euxine province in Turkey. This region extends to the western division of Caucasus, including the entire northern Anatolia. In the high altitudes of Euxine province, a formation of forests with large leaves occurs, mixed with conifers. In the Euxine vegetation areas, there has been no marked summer drought because of the rainfall which occurs even in summer months. Annual precipitation exceeds 1000 mm. in most places. Euxine province has been divided into two by Davis, as west and east by a boundary passing through the valley of Melet river
67
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68 which separates Eastern Black Sea part from the Middle Black Sea part. The part in the east is valled Colchic. The fundamental reason of this distinction is the density of Euxine species and the annual rainfall being markedly increased towards the east (DAVIS, 1971 : 17-18). As is known, annual amounts of precipitation as well as the share of the summer rainfall in the annual precipitation generally increases as one goes from the west to the east along the Black Sea coast. (In some meteorological stations, annual amounts of precipitation and the summer rainfall rates are as follows : Şile 767.2 mm., 11.9 %; Zonguldak 1232 mm., 18.2 %; İnebolu 1024.6 mm., 14.5 %; Sinop 643.6 mm., 14.0 %; Samsun 721.4 mm,, 14.9 %; Ordu 1135.2 mm., 19.7 %; Giresun 1267.7 mm., 19.2 %; Trabzon 798.1 mm., 15.6 %; Rize 2332.2 mm., 20.3 % ) . The dominant characteristic of the Euxine province is that the dominant vegetation cover is formed by mesophyl forests with large leaves and that the species with needle leaves are mixed with it. Although mesophyl forests occur in Hyrcanian province as in Euxine province, such species with needle leaves as Abies, Picea, and Pinus are not included in these forests1. In mesophyllic forests of Euxien province, there occur dominantly such species as Fagus orientalis, Rhododendron ponticum, Laurocerasus officinalis, Ilex colchica, Daphne pontica, Hedera helix, H. colchica, Vaccinium arctostaphylos, and Staphyla pinnata. (DAVIS, 1971 : 18; BROWICZ, 1988: 117-118). In the east of Melet river, the number of Euxine species and endemic species increases markedly. According to Davis, the species, the occurrence of which is limited by the colchic sector of Euxine province are such woody species as Betula medwedewii, Daphne glomerata, Epigaea gaultherioides, Osmanthus decorus, 1 Although the flora of Euxine province generally incilide the same species according to various researchers, it sometimes exhibits significant changes. For this reason, these species which exhibit changes according to researchers mentioned, are grouped as Euxine and Euxine-Hyrcanian and are given as a list (Table 1.) Browicz pointed out that the number of Euxine species was not completely determined, and that the number of trees and shrub species of this province was about 30,15 of which were evergreens.
69 Picea orientalis, Quercus pontica, Rhamnus imeretinus, Rhododendron caucasicum, R. smirnowii, R. ungerni, Rhodothamnus sessilifolius (the extension of this species is limited by the Eastern Alps), plus some herbaceous species. Although some of these species Davis classified as «Colchic» or «Süper Euxine» were endemic for Turkey, the habitat of some extended to Caucasus (DAVIS, 1971 : 17). Alpine flora of Colchic sector is closely related to Caucasus and shows very few floristic relations to the west of Turkey. On the other hand, Alpine flora of the western section in Euxine province is associated with the Irano -Turanian floral region of Turkey, and even with mountain flora of the Mediterranean (DAVIS, 1971 : 18). There has been a marked decrease of the Euxine species in the western section of Euxine province. Such species as Tilia tomentosa and Quercus frainetto from central Europe and Balkans are included into this region. Endemic plants which are less in number in western and middle section of Euxine belt than those in the eastern one, appear here, especially, in such elevated regions as Uludağ and İlgaz mountain. Zohary who suggested that Euxine-Hyrcanian area had been the shelter of many plants such as Zelkova, Pterocarya, Diospyros, and Albizia belonging to Tertiary flora at the end of Tertiary Period and in Pleistocene, and that it had also been the differentiation center of many plant species such as Sorbus, Acer and Quercus, divided the Euxine province into three horizontal groups in the light of information on climate, flora and vegetation (ZOHARY, 1971 : 44, 48-49; ZOHARY, 1973, 110, 123) (Figüre 5). a. The Eu-Euxinian Sector: The climax is characterized by beech forests. b. Sub-Euxinian Sector : It is characterized by climax forests of Carpinus-Quercus and Pinus sylvestris. The southern boundary of this sector extends along the southernmost boundary of Pinus sylvestris and/or Carpinus betulus' fields of occurrence. A few Eüxine oak species having close rela-
70 tions to Euro-Siberian species deserve attention in this sector. c. Arid Euxinian Sector: It is characterized by a steppe with trees where there are also scattered Euxine trees and shrubs. Zohary, pointing out that he was quite hesitant to use the term «steppe with trees», suggested that arboreal factors of the arid Euxine sector, including a larger part of the inner Anatolia, were destroyed largely by human hand. Today, the naked appearance of this region which is distinguished as arid-Euxine sector is the result of human interference which destroys largely its natural vegetation cover2. Some maquis elements which are the indices of Mediterranean climate exhibit an extension to the regions of Euxine province, represented by the northern slopes of mountainous areas of the Black Sea region. Researchers have differing opinions on the subject that maquis elements occur today in the Black Sea coasts. İnandık (İNANDIK, 1965: 11), Erinç (ERİNÇ, 1977: 106), and Atalay (ATALAY, 1983 : 89 and ATALAY, 1990 : 23-24) maintain that these are the relics which are extended to their formation areas of today under different climatic conditions in Pleistocene, and are preserved locally up to the present time. Davis has doubts about them that some elements belonging to the Mediterranean flora have probably extended northwards aiong the Anatolian diagonal which will be explained later. Davis suggested that Mediterranean elements in Black Sea were of two belts, that the first belt climbed approximately to 300 m. along the Black Sea coasts, and Euxine vegetation of this area were destroyed; that the second belt occurred in the south of Euxine mountain range 2 Davis points out that it is quite difficult to accept Zohary's suggestion that the boundaries of arid-Euxine sector are considerably larger, since at present time, plant species belonging to Irano-Turanian floral region are dominant in the floristic composition of this area. Davis who expresses his doubts about how many of these scattered trees can be considered Euxine relics (even EuroSiberian) maintains that such species as Pinus nigra together with Cistus laurifolius above the 1000 m. of altitude are considered as belonging to the Mediterranean (or sub-Mediterranean) floral region. (ZOHARY, 1971 : 50).
71
Figüre 5 — Plant formation exhibiting distribution in Turkey according to Zohary. 1 — Euxinian mesic deciduous and mixed forest 2 — Sub-Euxinian mesic deciduous and mixed forest 3 — Mediterranean subalpine forest of Cedretea libani 4 — Mediterranean woodland climax 5 — Xero-Euxinia.n steppe-forest 6 — Central Anatolian dwarf-shrub steppes of Artemisietea fragrantis anatolica 7 — Mosaics of Anatolian Artmisietea fragrantis armeniaca and Sub-Euxinian oak forest remnants 8 — Mesopotamian steppes of the Artmeisietea harbae-albeae mesopotamica 9 — Xerophilos deciduous steppe-forest of Quercetea brantii 10 — Mosaics of hydro-and halophytic vegetation partly on sandy ground 11 — Mediterranean steppe-maquis
and that the presence of some Mediterranean species such as cedar was quite surprising (DAVİS, 1971 : 26-27). On the other hand, Dönmez who described maquis as «a plant community composed of species with evergreen leaves and with stems of 1-2 m. high, developed especially in the coastal regions after the destruction of essential forest cover in the Mediterranean climatic regions», maintained that maquis existed with decreased
72 species in proportion to the decrease of the influence of Mediterranean climate in these areas; and that, when one went out of the real Mediterranean climatic region, maquis-decreased in species as well as lost its altitude. Dönmez pointed out that maquis which contained 18-20 species in the Mediterranean coast, could only reach approximately 800-900 m. in these areas; and that it could be represented by 13-14 species up to 500-600 m. in Aegean coasts, by 8-10 species up to 300-400 m. in Marmara Sea coasts, and only by 4-5 species up to 150-200 m. in the Black Sea costs (DÖNMEZ, 1968 : 176-184; DÖNMEZ, 1976 : 85-87). Zohary, in turn, suggested that Mediterranean maquis, present in such Euxine areas as Black Sea coasts, Sakarya and Kelkit valleys, were not of Pre-Pleistocene relics but actual invasions. Moreover, Zohary also maintained that maquis which occurred along the Black Sea coast was not native but was replaced by the climax vegetation destroyed by the human hand, that is, it was secondary (ZOHARY, 1971 : 45-48). These suggestions put forward on the subject of maquis formation in Turkey become clearer, if the doctorate theses carried out on the subject of plant geography in various regions where different climate types are dominant, under the guidance of Dönmez at various dates are taken into consideration. It appears that the maquis which are formed in the southern parts of Turkey from the Mediterranean coasts to the northern Black Sea coasts become less in species as well as lose its altitude as they approach the Black Sea region. Maquis which are represented by 18-19 species in Teke peninsula in the Mediterranean region of Eu-Mediterranean climate reach 1200 m. (SAYHAN, 1990 : 291-304); those in Aegean coasts are represented by 16-17 species and reach 800-850 m. (GÜNAL, 1986 : 307-323); in southern Marmara coasts they are represented by 15-16 species and reach 550-600 m. (GÜNGÖRDÜ 1982 : 211-220); those of western Black Sea coasts are represented by 11-12 species and reach 300-350 m. (YALÇIN, 1980 : 188-189); maquis in the coasts of the middle Black Sea are represented by 10-11 species and reach 400-500 m, (AKTAŞ, 1992: 230-234); vvhile those of eastern Black Sea coasts are represented by 6-7 species and reach 200 m. (ENGİN, 1992 : 231-236). The characteristics owned by the maquis are the result of the decrease in the
73 influence of the Mediterranean climate as one approaches the Black Sea coasts. The fact that the areas where maquis are formed are the ones where the native vegetation have been destroyed, makes the suggestions of Dönmez and Zohary, that maquis are not primary but secondary formations in these areas, justifiable. However, it is necessary to point out that in Turkey, apart from Liquidambar orientalis, such species as Fagus orientalis (KAYACIK, 1956: 112), Osmunda regalis (GÜNGÖRDÜ, 19861987: 131-133), Frangula alnus (GÜNGÖRDÜ, 1995: 35-39), Tilia rubra subsp. caucasica (AVCI, 1992 : 227-229) are found under different climatic conditions quite far away from their native regions. However, the habitat of ali of them are considerably limited and almost ali maintain their existence under very specific conditions in their new environment where they are fixed. The rather large habitat of these species in the earlier periods are restricted, probably depending on the climatic changes in Pleistocene period, and today, they are preserved in ideal places similar to those having the climatic changes of the ancient times Nevertheless, the maquis elements representing Mediterranean region have no interruption ali along the Black Sea coasts. This fact clarifies why they should not be considered as relict species. Although some maquis elements exist in the Black Sea coasts where the Euxine province is represented, the maquis formation of this area is not the real Mediterranean maquis formation but a pseudo-maquis one which is a scrub community with evergreen maquis species as well as deciduous ones under the influence of the Black Sea climate (DÖNMEZ, 1985 : 125). 2. Mediterranean Region : Mediterranean floral region is represented in Turkey by «the Eastern Mediterranean Province» which is considered to extend from the eastern half of Italy to Liban, and it reaches to Gallipoli peninsula in the Southern part of Thrace, including ali the Southern Anatolian coast. In these regions, the plant life is maintained for a considerable part of the year without any important interruption. Dry forests and maquis elements which are marked representatives of the Mediterranean climate, described as «dry and hot summers and warm and rainy vvinters» find their way into the above mentioned habitat. Zohary
74 points out that actual composition of Eastern Mediterranean vegetation and the limits of this floral region do not change markedly, since Pleistocene period, except by the changes caused by human activities in these regions since the beginning of the Pleistocene period and by the fluctuations of the climate (ZOHARY, 1971 : 48). The areas where Mediterranean floral region are represented in Turkey may be grouped under 3 headings3 : a — Western Anatolia b — Western and Middle Taurus Mountains c — Amanos Mountains a)
Western Anatolia:
Although the vegetation cover of this region which includes Eastern Aegean islands has some similarities to the plant communities thriving on Mediterranean coasts, some important Mediterranean species such as Abies cilicica and Cedrus libani do not exhibit any formation in this region. On the other hand, Mediterranean floral region in the Western Anatolia extends into to Irano-Turanian floral region by way of the Inner Western Anatolian region. The number of endemic plant species in Western Anatolia is relatively few. They occur mostly on mountainous areas included in the Aegean region (Malope anatolica, Chronathus orientalis, Eryngium thorifolium, and an alpine species, Linum aretioides). Moreover, Liquidambar orientalis attracts attention as a relict species whose habitat is limited by Southwestern Anatolia and Rhodes.
3 Davis has distinguished 3 sections in the Mediterranean floral region as Western Anatolia, Taurus Mountains, and Amanos Mountains. Here, the section which Davis deals with as «Taurus Mountains» contains western and Middle section of Taurus Mountains belt. (DAVİS, 1971 : 18-19).
75 b) Western and Middle Taurus Mountains : In this section of Taurus Mountains which forms the southern wing in Turkey of Alpine Orogenic belt, forest formation with needle leaves consisting of Pinus nigra, Abies cilicia, and Cedrus libani occur in high altitudes. Pinus brutia and maquis formation where pine trees are destroyed are dominant species under 10001200 m.4. However, among the maquis elements, those which are adapted to the contions more easily are preserved, as a result of destruction of maquis elements and the erosion of the soil in many places. The dominant elements of this plant community which is termed as «Garig» and consists of utterly arid poor and thin plant formation are Quercus coccifera, Juniperus oxycedrus, Phillyrea latifolia, Cistus sp., Poterium spinosum, and Thymus sp. In the Western and Middle Taurus Mountains, especially Bolkar Mountains, Tahtalı and Bereket Mountains are the places where endemic plants populate these areas densely. Plant species such as Phlomis, Sideritis, Origanum belonging to Labiatea family form most of these plant communities. c) Amanos
Mountains:
Amanos mountains occupy a special place in the flora of Eastern Mediterranean Province because of some climatic characteristics (such as the excess of summer rainfall and relative moisture ratio) and floral history. Among the endemic species which occur in this region, the most prominent ones are such highly different species as Ajuga postii, Origanum amanum, Helleborus 4 Polunin and Huxley classified the maquis into two groups as «High maquis» and «Low maquis». High maquis consisted of tali scrubs reaching 4-5 m. its elements are Arbutus unedo, A. atıdrachne, Quercus ilex, Juniperus phoenica, Cercis siliquastrum, Olea europea, Erica arborea, Phillyrea latifolia, Spartium junceum and Pinus halepensis (It is quite surprising that this element which is a tree species is included in the maquis elements.) The elements of Low maquis are of 1-2 m. at most. Some of the more important species include Pistacia lentiscus, Phillyrea media, Rosmarinus officinalis, Ruscus aculeatus, Paliurus spina christli, Cistus salviifolius, and C. creticus (POLUNİN, HUXLEY, 1978 : 9-11).
76 vesicarius and Vulfenia orientalis. Among them Vulfenia has only 4 more species which are known to occur in Western Himalayas, Eastern Balkans and Alps. Amanos mountains atract attention by having so many Euro -Siberian elements such as Taxus baccata, Fagus orientalis, Buxus sempervirens, Ilex aquifolium, Staphylea pinnata, Fraxinus excelsior and Smilax excelsa, besides their excess of endemic plant species (ZOHARY, 1973 : 156). According to Davis, «Anatolian Diagonal» which was a migratory route in Pleistocene played the most important part in the variety of the vegetational cover of the Amanos mountains (DAVİS, 1971 : 18-27). Along this route which will be explained in detail later in the following pages, Euxine species have migrated from north to south. 3. Irano-Turanian Region : Irano-Turanian floral region which includes Inner Anatolia and Eastern Anatolia plateaus, is bordered on the north by Euro-Siberian floral region and in the south and west by Mediterranean floral region. Although the rainfall of the inner parts are prevented by mountain ranges surrounding these areas by the north and south, annual precipitation rates change generally between 300-400 mm. Irano-Turanian region exhibiting the characteristics of steppe, mountain steppe, and semi-arid regions of Iran and central Asia, is mixed with Euro-Siberian and Mediterranean floral regions which surround it in Turkey. Davis pointed out that Irano-Turanian floral region in Turkey was separated into two vegetation areas except for the high mountaineous regions; that the first of them was a large outer belt formed by shrubs with deciduous leaves and by forests with the appearance of a park and that this outer belt vvas the essential forest area according to Louis (1939) and Walter (1956); that the second one consisted of essentially steppe areas. This region whicb is represented by the central Anatolian steppe around the Sal* Lake extends to Karaman, Niğde, Sivas and Çankırı with some interruptions. These steppe areas without trees cover an important part of the Eastern and Southeastern Anatolia. On the other hand, mountain steppes appear on the higher parts of Eastern Anatolia (DAVİS, 1965 : 22). It is quite surprising that the genuine steppe areas which were mentioned by Davis to have been observed around
77 the Salt Lake, were extended to Eskişehir, Karaman, Niğde, Sivas and Çankırı again by Davis himself, since these above-mentioned areas which appear today as steppe areas avoid of trees and with bare landscapes are not natural steppe areas caused by conditions of climate and soil, but antropogenic steppe areas resulted from the destruction of forests by people due to various causes (AYTUĞ, 1967 and 1970; DÖNMEZ, 1985 : 129-130; KAYACIK and AYTUĞ, 1968; USLU, 1970; ZOHARY, 1971 : 45). Cullen who analyzed the extension of species for the IranoTuranian floral region in the first volume of «Flora of Turkey», observed a floral interruption in regions forming the transition areas between Inner Anatolian and Eastern Anatolian regions. Davis termed this line where the interruption was observed as «Anatolian Diagonal». This line extends to middle Taurus mountain beginning from the Gümüşhane-Bayburt regions which occupy the rain shadow of Eastern Black Sea coastal mountains (Figüre 4). This line separates into two branches in the southern part of Tahtalı and Binboğa mountains (approximately 38th parallel). One of these branches extends to Amanos mountains and the other to Aladağlar and Bolkar mountains. The habitat of 550 species in the first volume has been analyzed and it has been observed that 135 species do not cross the western part of this diagonal or that only one or two of these species have occurred scattered in the western part of this line; and that 228 species have not been found in the eastern part of this diagonal (again with the exception of one or two species). Although, according to Davis, the eastern part of this diagonal, except for the Southeastern Anatolia, was more mountainous generally than its western part, the climate and some other characteristics of physical geography were not sufficient to explain this floral interruption. Davis maintained that this fact which was first realized by Cullen and was interpreted by him self, could be related to the paleogeography of Anatolia (DAVIS, 1971 : 19-20). Davis who suggested that, based on Kosswig (KOSSWIG, 1967 : 313-324), during Eocene and Oligocene, Anatolia was a region of lower islands related to innumerable seas between Tethys and Paratethys, pointed out that, although during Miocene the Ana-
78 tolian part lying in the west of the diagonal had been mostly of flat land, the sea and marine conditions had continued in the Eastern Anatolia. During Pleistocene, when Mesopotamian sea changed into the lower areas of today (actual Syrian deserts), the last link between Indian Ocean and Tethys receding (today's Mediterranean) had been lost forever5. Thus, Davis assuming that the mountainous areas of Eastern Anatolia plateau were not formed before the transition of Miocene-Pliocene and that, if this assumption, were true, Irano-Turanian flora extended from Iran to Eastern Anatolia during Pliocene, pointed out that in the same period, the extension of Mediterranean Sea towards the east had stopped and that the aridness of the Eastern Anatolian climate should have been increased. Doubtlessly, interglacial (inter pluvial) period of Quaternary had guided the change of Irano-Turanian flora and its migration to the west. Apart from Erinç who pointed out that marine conditions were generally dominant in Eastern Anatolia and that starting from the beginning of the Miocene, these conditions were lost (ERİNÇ, 1953: 7-11), Şengör, also, suggested that Eastern Anatolia and Iran were the stage of a widespread transgression coming from the west, in the period when Oligocene ended and Miocene began. According to Şengör, these areas remained under the sea at least until Seravalian (end of mid -Miocene), and it was recognized that in upper Miocene, a general regression had begun due to the precipitates from the lakes and fluvial precipitates över the prous rocks of marine origin (ŞENGÖR, 1980 : 14-15). These suggestions of Erinç and Şengör may help clarify Davis's interpretation a little more on the subject of oecurrence of Irano-Turanian flora in Turkey.
5 Although it was pointed out that the separation of Tethys into two, occurred during Eocene and Oligocene, Atalay maintained that this separation occurred at the end of Oligocene when the connection of Oligocene with the sounth had been interrupted. During Oligocene, the movement of Alp orogenic became increasingly violent and reached the paroxismal stage in upper Oligocene and regressions became important. The larger part of Turkey had almost completely become land except Southwest, Southeast Anatolia and Van Dake and İğdır environment of Eastern Anatolia ( A T A L A Y , 1987 : 382-383).
79 However, Ekim and Güner reviewed later the published 8 volumes of «Flora of Turkey» for the purpose of clarifying the problem of Anatolian Diagonal, interpreted by Davis for the Irano-Turanian flora (EKİM and GÜNER, 1986 : 69-77). Nevertheless this review did not take into consideration such species as Euxine ones occurring in the mentioned area, lignous species characteristic of Mediterranean Sea, numerous herbaceous species occurring in lower areas of Mediterranean Sea, species belonging to Mesopotamia, halophyte species growing mostly in the salty environments of the middle Anatolia as well as some plants having such special characteristics as infra-specific taxons (plants with different geographical distrubution, at the subspecies) although their occurrence for the diagonal were relatively interesting. Ekim and Güner, who pointed out that this review was subjective to some extent, found the number of species occurring in the west of the diagonal for the first volume quite different from those mentioned by Davis. East of the West of the Över the Diagonal Diagonal Diagonal Davis Ekim and Güner
135 123
228 114
62
This situation has resulted from the difference in the criteria. However, the result stemming from the occurrence of species formed by herbaceous perennials analyzed in these 8 volumes confirms the fact that there has really been an interruption in the occurrence of plants in the inner parts of Turkey. Ekim and Güner point out that the cause of this interruption is not related to the paleogeography of Anatolia but to the altitude, climate and habitat of Anatolia, since nearly half of the species growing in the eastern part of the diagonal occurs generally över 2000 m. Almost ali of these species growing över 2000 m. are concentrated mostly on the eastern, most part of the eastern Anatolia. This characteristic which appears in the distribution of the species occurring in the interior parts of Turkey and which is not so surprising as suggested by Davis, must be related to the dif-
80 ferences in the growth conditions (climate, soil and geomorphic properties) of the plants of Inner and eastern Anatolia which are two different geographic regions, since the geographic regional boundary beginning from Kızıldağ in northeast and extending to the southwest towards Tahtalı mountain, roughly in the direction of northeast-southwest of these two regions, the geographical characteristics of which are markedly different, corresponds generally the Anatolian diagonal of Davis. The factors which from the growth conditions of Inner and Eastern Anatolia regions will be roughly dealt with in the following. The climate of Eastern Anatolia which is manifested as severely Continental is different from that of Inner Anatolia. The Eastern anatolia region where the highest temperature differences are observed has been the most Continental part of Turkey as a whole. On the other hand, the annual temparature differences in Inner Anatolia which is also a Continental region, are less than 5-6°C than the Eastern Anatolia. This condition is related to the Continental proportion of this area which is less as compared to Eastern Anatolia (DÖNMEZ, 1990 : 58-60; ERİNÇ, 1953 : 20-30; ERİNÇ 1969 : 304-306). If the real annual distribution of the mean temperatures of the Inner and Eastern Anatolia regions is taken into consideration, as one approaches to the Eastern Anatolian region which is more continental and higher, there has been observed a marked decrease in the annual mean temperature which occurs between 8-12°C in the Inner Anatolian area, and in the east on the Kars plateaus these values fail below 4°C (ERİNÇ, 1969: 314-320). Again, the frequency of temperatures below 0°C and the mean number of days with frost are lower in the Inner Anatolia than the Eastern Anatolian region. (The number of days with frost in some meteorological stations of these regions are as follows : Kars 181, Erzurum 154, Van 132, Yozgat 106, Konya 100, Kırşehir 99, Ankara 75 DMİ, 1974). The differences occurring between the Inner Anatolia and Eastern Anatolian regions as to the temperature, appear when the characteristics related to precipitation are considered. Although the amount of rainfall exhibits considerable alterations in short
81 distances depending on the relief, (while the high mountainous areas of the region ha ve less than 1000 mm. of rainfall, such lower areas as İğdır depression have 250-300 mm. of rainfall) Eastern Anatolian region has more precipitation than the Inner Anatolian region. These two regions have differing values regarding the mean number of days with snowfall. In the Eastern Anatolian region, these values are considerably higher (Ankara 13.9, Konya 11.0, Kırşehir 12.8, Kars 44.7, Erzurum 50.1, Van 34.7). The number of snow-covered days varies with 20-40 in the Inner Anatolian region (Ankara 21.5, Konya 21.0, Kırşehir 22.5). These values reach their highest in the Eastern Anatolian region (Kars 107.7, Erzurum 113.6, Van 79.0). Meteorological stations belonging to Inner and Eastern Anatolia have very different moisture indices according to Thornthwaite method. The increase in the moisture indices as one goes from Inner Anatolia to Eastern Anatolia, suggests that the semiarid conditions of the Inner Anatolia decrease toward the east, and that even in the eastern half of the Eastern Anatolia they are replaced by semi-moist or moist conditions. Likewise, according to Erinç's rainfall efficiency index, an important part of Inner Anatolia is semi-arid while Eastern Anatolian region is semi-moist (ERİNÇ, 1969: 358-361; ERİNÇ, 1977: 14). The presence of soil is very important for the vast majority of plants and for ali plant formations. For this reason, it is clear that the soil is one of the most important factors, apart from the climate, in the distribution of the vegetation cover. Different soil conditions produce local or regional changes in the large plant community areas or belts resulted from certain climatic conditions (ERİNÇ, 1977 : 37). While mostly lithosols and brown forest soils occur largely in the Eastern Anatolian region, brown soils are more extensive in the Inner Anatolian Region. The distribution areas of other soil types such as lithosols, rendzinas and hydromorphic salty alluvial soils are more restricted (ERİNÇ, 1977 : 2425; ATALAY, 1989 : 384-385).
Review
F.
S
82 The vegetation cover in an area has a relation to the relief, though indirectly, except the climatic and soil conditions. This relation occurs depending on the changes in the temperature and precipitation conditions caused by the differences in the relief. Altitude and exposure cause the changes mentioned above. Among the geographical factors which cause the Eastern Anatolia to have a very marked characteristic, and which form the basis of this unit, the mean altitude of the region comes first (ERİNÇ, 1953 : 4). The large part of this region is generally covered by vast plains reaching above 2000 m. (Figüre 6). These plains are interrupted from place to place by narrow depressions or high mountain ranges. However, even İğdır plain which is the lowest depression (approximately 875 m.) of Eastern Anatolia is scarcely different from the mean altitude of the Inner Anatolia (1000 m). On the other hand, some depressions forming the lower areas of Eastern Anatolia (for example, Başkale 2300 m., Erzurum plain 1750-1800 m.) are at the same altitude as the summits of some mountains found in Inner Anatolia. These characteristics reveal with clarity that Eastern Anatolia is higher than Inner Anatolia. Ali of these differences in the growing conditions which appear as very important factors in the distribution of the vegetation cover, and which are mentioned above in general lines, will naturally create some important changes between vegetation covers of the two regions. It is clear that ali plants, whether belonging to forest, shrub, or herbaceous formations, will occur generally according to the growing conditions mentioned before. Moreover, dealing with the climatic conditions of these regions (which probably will constitute to subject of another research paper), especially the analysis of the temperature and precipitation values according to the daily data, will explain better the differences present between these regions. Hovvever, these characteristics which appear even in a general overview, have an important value on the subject of the interpretation of the Anatolian diagonal, the presence of which was mentioned by Davis et al., since transition areas of these two regions with such different habitat properties having different vegetation covers and regions showing more distinguishing characteristics as compared to the transition areas should have been the result of the differences mentioned.
84 The Irano-Turanian floral region of Turkey which attracts attention as to its distribution of species is the richest region of Turkey regarding its plant species and the number of endemics is rather considerable. Especially, the endemic plant species belonging to the genera such as Astragalus, Silene Hypericum, Verbascum, Phlomis and Achilles occur mostly in Irano-Turanian floral region (ANŞİN, 1983 : 327). The areas in the Eastern Anatolia Erzurum, Erzincan and its environment, and areas in the south of Van Lake which are included in this floral region, and Çankırı and Sivas which are in Inner Anatolia deserve attention as the centers of endemism. Transition Areas : The transition areas which remain among three floral regions represented in Turkey are of a special importance as to the vegetation cover. These transition areas have both a number of endemic plants and they are characterized by their own endemics. These areas deserve attention as the regions where hybrid species occur mostly (DAVIS, 1971 : 23-26). Lakes District vvhich extends between Mediterranean floral region and Irano-Turanian floral region may be given as an example of this characteristic. In the western section of this district which is the habitat of Quercus vulcanica, an endemic species, there appear many hybrid oak species (Quercus cerris x Q. ithaburensis subsp. macrolepis, Q. cerris x Q. trojana, Q. cerris x Q. pubescens, Q. trojana x Q. infectoria, Q. infectoria subsp. boisseri x Q. pubescens) (AVCI, 1990).
Table 1 — Euxine and Euxine - Hyrcanian Species Aceording- to Davis Zohary and Browi.cz. Davis Abies bornmuelleriana Abies nordmanniana Acer campestre Acer cappadocicum Acer cinerascens Acer hyrcanum Acer ibericum Acer platanoides Acer pseudoplatanus Acer sosnovskyi Acer tataricum Acer trautvetteri Albizia julibrissin Alnus barbata Alnus glutinosa Alnus subcordata Amelanchier ovalis Andrachne colchica Betula litwinowii Betula medwediewii Betula pendula Buxus sempervirens Carpinus betulus Carpinus orientalis Castanea sativa Celtis glabrata Cerasus avium Cerasus sintenisii Coraus australis Cornus mas Corylus avellana Corylus colurna Corylus pontica Cotinus coggygria Cotoneaster racemiflorus Crataegus microphylla Crataegus pentagyna Daphne caucasica Daphne glomerata Daphne mezereum Daphne pontica Diospyros lotus Epigaea gaultheroides
+ +
Euxine Zohary + +
Browicz
Euxioe-Hyrcanian Zohary Browicz
+ + + + + + +
+
+ + + +
+
+
+ + +
+ + + + + +
+
+
+
+ + + + +
+ +
+
+ + +
+ +
+ + +
+
+ +
+ + +
+ + +
+
+
+
+ +
+ +
+ +
+ +
86 Table 1 — (Continuous) Euxine
Davis Euonymus latifolius Euonymus europaeus Fagus orientalis Frangula alnus Fraxinus excelsior Fraxinus ornus Hedera colchica Hedera helix Hippophae rhamnoides Hypericum androsaemum Hypericum calycinum Hypericum xylosteifolium Ilex aquifolium Ilex colchica Jasminum officinale Juglans regia Juniperus communis Juniperus oblanga Juniperus sabina Laurocerasus officinalis Ligustrum vulgare Lonicera caucasica Malus orientalis Mespilus germanica Osmanthus decorus Ostrya carpinifolia Philadelphus caucasicus Picea orientalis Pinus nigra Pinus sylvestris Populus canescens Prunus divericata Pterocarya firaxinifolia Punica granatum Pyracantha coccinea Pyrus communis Pyrus elaeagrifolia Quercus cerris Quercus dalechampii Quercus frainetto Quercus hartwissiana Quercus robur Quercus petraea
Zohary
Brovvicz
+
+ +
+ + +
+
Euxine-Hyrcanian Zohary Brovvicz • + + + + + + +
+ +
•
+
+ + + +
+
+ + + +
+ + +
+
+ +
+ + +
+
+
+ + + +
+
-+
+
+
+
+
+ + +
+ + +
+ +
+
+ + + + + + +
+
87 Table 1 — (Continuous)
Davis Quercus pontica Quercus pubescens Rhamnus catharticus Rhamnus depressus Rhamnus imeretinus Rhamnus microcarpus Rhamnus pallasii Rhamnus pontica Rhamnus spathulifolia Ribes bieberstenii Rhododendron caucasicum Rhododendron flavum Rhododendron ungernii Rhododendron ponticum Rhododendron smirnovii Rhodothamnus sessilifolius Smilax excelsa Sorbus armeniaca Sorbus aucuparia Sorbus colchica Sorbus dualis Sorbus graeca Sorbus subfusca Sorbus torminalis Spiraea hypericifolia Staphyla colchica Staphyla pinnata Syringa persica Taxus baccata Tilia cordota Tilia rubra IJlmus campestris Ulmus leavis Vaccinium arctostophylos Viburnum tantana Viburnum opulus Viburnum orientale Zelkova carpinifolia
Euxine Zohary + +
Browicz +
Euxine-Hyrcanian Zohary Browicz
+ + +
+ + +
+ + + +
+ + +
+ + +
+ + + + + +
+
+
+
+ +
+ + + +
+
+
+
+ + + +
+ + + + + + + + + + +
+
+
+
+
+ +
+
88
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