13H3
Pyramid formations in fluvial-glacial deposits (Stob pyramids)
Relationships with habitat classifications. EUNIS: H3.1В2 Bare siliceous inland cliffs; PAL. CLASS.: 62.42 Siliceous bare inland cliffs.
Conservation status. None.
Category. Critically endangered [CR – C3 D3 F3 G3 H3].
General characteristics. This habitat type is a complex composition of sharp, needle-like, but mainly pyramidal or conical earth shapes. Some of them on top have ‘stone hats” of 0,8–1,0 m in diameter, thus resembling mushrooms. They are sculptured in 30–40 m thick, old Quaternary villafranchian fluvial-glacial deposits. The average height is 6–10 m, and the maximum height is 12 m. A significant number of them are united at their basis and form picturesque and very diverse groups. Apart from the diversity of shapes, the colours of the sediments are different, varying from pale yellow to dark brown and red. This unique Bulgarian habitat is situated in the northwestern part of South-West Rila Mts. (Kapatnitsa part), above Stob village, from where the name originates, the Stob pyramids. A small part of the habitat is on a northern slope, but most of the pyramids are on a southern slope. Formations without vegetation or covered with communities in their primary stages of development are most typical. The separate plant individuals or the primary coenoses scattered on the pyramids consist of species from the more advanced plant communities located mainly at the their bases. The xerothermic elements are from the sub-Mediterranean vegetation of the hornbeam-Balkan durmast belt in the Bulgarian mountains. The forest coenoses consist of Quercus dalechampii, with the participation of Carpinus orientalis, Fraxinus ornus, Pyrus amygdaliformis, P. elaeagrifolia, Sorbus torminalis, and Ulmus minor. Among the shrubs are Cornus mas, Corylus avellana, Crataegus monogyna, Ligustrum vulgare, and in stony and eroded places or rocks, Colutea arborescens, Cotinus coggygria, Juniperus communis, J. oxycedrus, Paliurus spina-christi, Sorbus aria, Syringa vulgaris occur.Together with the herbaceous species typical for the forest coenoses like Brachypodium sylvaticum, Cruciata laevipes, Festuca heterophylla, Galium pseudaristatum, Poa nemoralis,xerothermic elements are widely distributed, such as Aira elegantissima, Alyssum alyssoides, A. corymbosoides, A. murale, Arabis turrita, Astragalus hamosus, A. onobrychis, Bromus squarrosus, B. sterilis, Cardamine hirsuta, Cerastium brachypetalum, C. petricola, C. velenovskyi, Cleistogenes serotina, Comandra elegans, Coronilla varia, Cyclamen hederifolium, Cynosurus echinatus, Dianthus armeria, D. pinifolius, Draba muralis , Festuca valesiaca, Genista carinalis, G. tinctoria, Goniolimon tataricum, Koeleria nitidula, K. splendens, Lathyrus laxiflorus, L. sphaericus, Melica uniflora, Minuartia hirsuta, Onobrychis lasiostachya, Petrorhagia prolifera, Poa bulbosa, Potentilla laciniosa, P. micrantha, P. neglecta, Psilurus incurvus, Scabiosa columbaria, S. triniifolia, Scolymus hispanicus, Scorzonera hispanica, Senecio jacobaea, Stipa capillata, Tragopogon dubius, Trifolium dubium, T. patens, T. scabrum, Valerianella carinata, Veronica chamaedrys, V. hederifolia, V. triphyllos, Vicia lathyroides, Vulpia myuros. The ferns Asplenium adiantum-nigrum, A. trichomanes, and succulents Sedum acre, S. cepaea, S. hispanicum also occur.
Characteristic taxa.
- Vascular plants: Asplenium adiantum-nigrum, Alyssum alyssoides, A. corymbosoides, Asplenium trichomanes, Brachypodium sylvaticum, Carpinus orientalis, Colutea arborescens, Cotinus coggygria, Cruciata laevipes, Festuca heterophylla, Fraxinus ornus, Galium pseudaristatum, Goniolimon tataricum, Juniperus communis, J. oxycedrus, Minuartia hirsuta, Paliurus spina-christi, Poa nemoralis, Pyrus amygdaliformis, P. elaeagrifolia, Quercus dalechampii, Sedum acre, S. cepaea, S. hispanicum , Sorbus aria, S. torminalis, Syringa vulgaris, Ulmus minor.
Distribution in Bulgaria. Rila Mts. – northwesterm part of Kapatnitsa area, above Stob village, Kyustendil district; 500–650 m alt.
Conservation importance. Natural phenomenon and unique habitat type for Bulgaria - earth shapes without vegetation or with single plants and closed coenoses.
Threats. Infrastructure development, erosion processes, planting of alien species.
Conservation measures taken. Stobski Piramidy Nature monument has been established.
Conservation measures needed. Phytocoenological studies and monitoring, regulated access for the tourists.
References. Georgiev 1988.
Authors: Veska Roussakova, Dimitar Dimitrov
