07E1

E. Herbaceous communities and communities of lichens and mosses

Danubian loess steppes

Relationships with habitat classifications. EUNIS: E1.2C Pannonic loess steppe grasslands; PAL. CLASS.: 34.91 Pannonic loess steppe grasslands; HD 92/43: 6250 *Pannonic loess steppe grasslands; Bondev (1991): Xerothermal grass communities with a prevalence of Dichantieta ischemi, Poaeta bulbosae, Poaeta cocinnae, Chrysopogoneta grylli and Ephemereta.

Conservation status. BDA, BC, HD.

Category. Endangered [EN – A1, 2 B1 C3 D2 E2 F2 G2 H3 I].

General characteristics. This habitat type occurs on the elevations in the northern part of the Danubian plain, on typical loess with a thickness of 30–50 up to 100–120 m. In these places the loess cover forms typical shapes – “hunches” (garbitsi) (near Oryahovo and Kozloduy towns, Gorni Tsibar and Dolni Tsibar villages) and large loess plateaus (Zlatiyata, Ravnisteto, the elevations near Somovit village, Nikopol and Svistov towns, northwards from Byala town). Between Kozloduy town and Gorni Tsibar village (and in other places in NW Bulgaria), the loess cover ends at the terraces of the Danube with a vertical wall 80 m high and 4 km long. The loess steppes are distributed on the rounded ridges (the heights of these loess “hunches” at Ostrov village and Oryahovo town reaching 220 m alt.) and on the less tilted slopes where the erosion processes are weak. The soils are castanic and typical chernozems, in various stages of degradation. These soils are relatively rich, but dry. On the strongly eroded slopes with calcareous outcrops the loess steppes gradually turn into petrophytic steppes. According to the soil strength and degree of erosion various loess steppe coenoses can be observed, dominated mainly by grasses. Closed and densely tufted herbaceous communities prevail on the richest and least eroded soils. The following major species Chrysopogon gryllus (association Thymo urumovii–Chrysopogonetum), Festuca valesiaca, F. rupicola and Stipa tirsa occur. The height of the main herbaceous layer (the tufts of Chrysopogon gryllus) reaches up to 1.80 m. A second layer of lower grasses also exists (Poa spp., Festuca spp., Koeleria spp.). The most representative loess steppes are in the area of Nikopol plateau and on the right bank of Vit river between Pleven town and Somovit village (Korabiiskiy Val locality). Typical steppe species (Pontic-Pannonic elements) participate in the species composition: Astragalus dasyanthus, A. pubiflorus, Centaurea stereophylla, Crocus reticulatus, Nepeta parviflora, and Salvia nutans. Some regional endemics also occur, Chamaecytisus kovacevii and Stachys arenariaeformis. As a result of long-lasting, intensive grazing in the vicinity of the settlements, e.g. near Ostrov village, the coenoses of Chrysopogon gryllus have been replaced by the more plastic, but poorer in species, coenoses of Bothriochloa ischaemum(= Dichanthium ischaemum). Species that are not suitable for grazing for various reasons (Artemisia austriaca, Eryngium campestre, Euphorbia nicaeensis, Thymus callieri subsp. urumovii) prevail in the composition of the latter but some primary elements like Astragalus austriacus also occur. In the western part of the Danubian plain (the area of Lom and Kozloduy towns) most of the typical pontic steppe species disappear. The open communities of the steep loess outcrops are very typical for these places. Large tufts of Artemisia campestris, Centaurea rumelica, Chamaecytisus supinus, Kochia prostrata, and Peganum harmala develop in the loess crevices. On the loess “hunches” on the top of the steep slopes these coenoses are closed and some grass species (Agropyron cristatum, Stipa capillata) have considerable participation. Most of the steppes on the loess plateaus were ploughed in the Middle Ages and a very small part has been preserved until now, mainly on places that cannot be cultivated. The steppes that have survived are subjected to degradation processes.

Characteristic taxa.

Distribution in Bulgaria. Only in the Danubian plain – in the area of distribution of the typical (dust) loess on top of the loess plateaus and “hunches” in the heights between the Danube to the North and the line between Brusartsi town, Hayredin village, Byala Slatina town, Pleven town, Levski town, Polski Trambesh town, Byala town and Russe to the South.

Conservation importance. Endangered habitat in Bulgaria, covering relatively small areas and subjected to various negative impacts. This habitat is of particular importance for the protection of the isolated localities of many rare, endangered and protected steppe species – Astragalus dasyanthus, A. pubiflorus, Centaurea rumelica, Chamaecytisus kovacevii, Stachys arenariaeformis,as well as fungi of conservation value (e.g. Amanita vittadinii).

Threats. Most of the steppes were ploughed in the past and turned into cultivated land. In the areas close to the human settlements grazing has had a negative impact. It caused the extinction of some relic, steppe species and in the same time increasing of the number of more mobile, thorny, poisonous and ruderal species. Natural erosion processes, fires, forest planting (mostly with black locust), and to a lower degree communication systems (roads, electric transmitters, etc.) also have negative impact.

Conservation measures taken. The habitat is included in Annex № 1 of the national Biodiversity Act. The largest and most representative localities in the area of Russe, Nikopol, Oryahovo and Kozloduy towns are included in sites of the European Ecological Network NATURA 2000 in Bulgaria.

Conservation measures needed. Investigation and monitoring of the preserved loess steppe communities.

References. Ganchev et al. 1964; Jordanoff 1936; Tzonev 2002.

Author: Rossen Tzonev


Danubian loess steppess (distribution map)