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and forest-steppes are also found in Bulgaria. Neither the floristic composition nor the
general outlook of the plant communities along both sides of the river Danube differ
significantly from the Ukrainian Black Sea coastal steppes. A number of Pontic and
ancient Mediterranean species reach to the east only the Danubian plain but are not found
in Ukraine (Доне в, 2002). In the southernmost part o f the Euro-Asiatic steppe and
forest-steppe area are located the flat terrains o f Dobrudza and Northern Bulgaria that are
related to the Lower Danubian province (Бондев. 2002). Namely on these territories
some of the xerophyle species reach the outermost localities outside the primary center of
distribution or are remnants of the disjunction of their primary areas. The steppe elements
in the Bulgarian flora originate from Southern Europe, Central and Asia Minor, reaching
various parts of the country dependent on their own ecological plasticity.
PATTERNS OF DISTRIBUTION
The irradiation of steppe vegetation type is realized at a wide front without
geographical barriers, so that the Dobrudza area and the Danube Plain are the richest in
steppe species (Fig. 2). The xerothermic species of the adjacent Northern Black Sea coast
belong also to this group. Several representatives o f this genus -
Astragalus glaucus
B ieb ..
A. exscapus
L., /1.
varias
S. Gmel.,
A, corniculatus
B ieb .,ri.
contortuplicatus
L.
are distributed only in the Danube Plain and along the Northern Black Sea coast.
Nowadays in these territories mainly on calcareous terrains with thin humic-
carbonate soils are preserved primary, modified and poor steppe floristic complexes.
These places are considered natural, and this migration stage o f the steppe geoelements
as (lie first one. Such primary steppe floristic complexes composed of
Dichantitun
ischaemwn
(L„)Roberty.
Chrysopogion gryilus
(L.)Trin,
Stipa pulcherrima
C. K och ,
Artemisia absinthium
L.,
A. pontica
L.,
Salvia pratensis
L.,
Glycyrrhysa glabra
L.
Astragalus pubiflorus
DC,
A. asper
Jacq,.
A.austriacus
Jacq.,
A. corniculatus, A.
ponticus
Pal l , are preserved in many places on the ridges o f the calcareous hills in the
Danube Plain.
On places free of tree vegetation and on the ancient Thracian mounds amidst the
arable land, which resemble peculiar refugia for rare plant elements, are found
Agropyron brancizae
Pantu et Sol acol u,
Paeonia tenwfofm
L.,
Adonis vernalis
L. /1,
wolgensis
Sl ev. ,
Salvia nutans
L,,
Potentilla emili-popu
Nvarady,
Potentilla
astracanica
Jacq., and a number of Astragalus species
- A. glaucus, A. vesicarius
L.,
A.
varitis, A. spruneri
B o iss.,
A. onobrychis
L., /1.
corniculatus, A. austriacus
. and
A.
ponticus.
These species probably originated and differentiated morphologically within
the borders of the cold steppe vegetation, with a subsequent stabilization in specific
ecological niches.
The present day territories with a steppe flora are raflier poor in species mainly as a
result of the pronounced climatic change towards cooling and higher humidity also
changes in the soil conditions, and the direct human impact as well. This distribution of
the steppe geoeJements is a secondary one.
Most of the plain-steppe species of
Astragalus
demonstrate clear relations with the
mountainous xerophyte flora - one part with the Caucasian species, another part with the
Anatolian-Tjanshan ones. The first group has migrated from the plains to middle altitudes
25
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