07H3

H. Inland rock habitats

Silicate rocks with hasmophytic vegetation

Relationships with habitat classifications. EUNIS: H3.152 Carpatho-Balkan-Rhodopi campion siliceous cliffs; PAL. CLASS.: 62.252 Carpatho-Balkan-Rhodopi campion siliceous cliffs; HD 92/43: 8220 Siliceous rocky slopes with hasmophytic vegetation.

Conservation status. BDA, HD.

Category. Vulnerable [VU – A1, 2 B2 D2 H2 I J].

General characteristics. This habitat type encompasses vertical or very steep (65°–90°) silicate (granite, gneiss, riolite) rock walls and the crevices in them. The conditions at which the plants and other organisms occur are extremely unfavourable, hence the natural selection is very strong and the abundance of the species is low. The temperature during day and night and during the different seasons varies considerably. The substrate humidity can be almost close to zero or can be permanently high. The plants can very often be subjected to strong winds and the snow cover can be absent. Soil cover is absent or is very poorly developed. Small quantities of fine soil accumulate in some crevices in the rocks, and humidity is retained. The direct sunlight can be avoided but the conditions remain unfavourable for the plant development. Apart from the altitude other factors that have significant impact on the floristic cover and structure of the rock phytocoenoses are acidity of the rocks, exposure, slope, size of the crevices, running water or humidity of the substrate. The projective cover of the vegetation is mostly extremely low; separate individuals or small groups of plants can be distant from each other without contact. The isolation and the need for specific adaptation to the environment are the prerequisites for endemism. However, on silicate rocks it is much more limited than on calcareous rocks. Silicate rocks constitute a significant part of the surface of the alpine belt and to a smaller degree in the subalpine belt/ upper subalpine belt in Rila Mts.. Their distribution in Pirin Mts. and in other Bulgarian mountains is much more limited. The most frequent species in the phytocoenoses of this group in the alpine vegetation are Anthemis orbelica, Potentilla haynaldiana, Saxifraga pedemontana subsp. cymosa,S.pseudosancta (= S. juniperifolia), Silene lerchenfeldiana.Although the exposure has a more limited impact on the composition of the vegetation under consideration, the two main species still prefer sunny places: Silene lerchenfeldiana and Potentilla haynaldiana. At the same time the exposure of most of the rock complexes is northern or with a northern component, more rarely it is eastern or western and very rarely - southern. The projective cover of the vegetation varies considerably, from 1–30% (60%). In this conditions Allium melanantherum, Anthemis carpatica, Armeria alpina, Aster alpinus, Campanula rotundifolia, Cryptogramma crispa, Doronicum columnae, Gentiana frigida, Geum bulgaricum, Huperzia selago, Jovibarba heuffelii, Polytrichum juniperinum, Rhodiola rosea, Saxifraga bryoides, S. exarata, S. retusa, Sedum annuum etc. are also more frequent species. Apart from the typical hasmophytes, most of the species of the surrounding phytocoenoses of the alpine vegetation that are better developed, have pioneer characteristics. Species from surrounding herbaceous and shrub coenoses grow in the crevices, where little fine soil accumulates, and also on the almost vertical rocks. Such species are Agrostis rupestris, Avenula versicolor, Bruckenthalia spiculifolia, Carex curvula, C. kitaibeliana, Empetrum nigrum, Festuca riloensis, Hieracium alpicola, Jasione laevis subsp. orbiculata, Juncus trifidus, Juniperus sibirica, Minuartia recurva subsp. orbelica, M. stojanovii (Balkan endemic that occurs in Bulgaria only in South Pirin Mts.), Pinus mugo, Primula minima, Ranunculus crenatus, Sesleria coerulans, Sesleria comosa, Vaccinium uliginosum etc. A relatively high number of moss species develop on the silicate rocks: Dicranum scoparium, Mnium blittii, Polytrichastrum alpinum, Polytrichum juniperinum, etc. All these and some other species make considerably diverse plant groupings that can be classified in different associations. At lower altitudes, in the lower sub-alpine sub-belt and in the belts of the beech forests, on steep and shady rocks and rock crevices with northern exposure occur Asplenium septentrionale, A. viride, Centaurea nervosa, Clenidium molluscum, Cystopteris fragilis, Distichium capilaceum, Haberlea rhodopensis, Helianthemum nummularium, Hylocomium proliferum, Hypnum triquetrum, Minuartia saxifraga, Plagiochila asplenioides, Plagiopus oederianus, Polypodium vulgare, Polytrichum juniperinum, Rosa pendulina, Scrophularia aestivalis, Selaginella helvetica, Sempervivum erythraeum, S. leucanthum etc. A considerable number of the species mentioned above occur in many Bulgarian mountains. Open silicate rocks, mainly on limited areas, occur everywhere but they are mainly on the high mountain ridges. Their exposure is different and the species composition is poor. The typical hasmophytes are few. Very often species whose distribution is related to screes occur there. Together with the mosses Alchemilla asteroantha, A. jumrukczalica, A. pyrenaica, Allium carinatum, A. victorialis, Androsace obtusifolia, Asperula aristata, Campanula scheuchzeri, Centaurea kernerana, Cerastium decalvans, Galium heldreichii, Gentiana acaulis, Huperzia selago, Minuartia bulgarica, Potentilla haynaldiana, P. rupestris, Rhodiola rosea, Rhododendron myrtifolium, Satureja pilosa, Saxifraga bryoides, S. exarata,Saxifraga pseudosancta (= Saxifraga juniperifolia), Sedum album, Seseli bulgaricum, Symphyandra wanneri, Valeriana tripteris etc. also occur. The silicate rocks in Vitosha Mts. do not have their own specificities. In Rhodopi Mts. some rare species from the Bulgarian flora occur such as Campanula rotundifolia, Petkovia orphanidea, Seseli rhodopeum, Symphyandra wanneri, etc. At lower altitudes, below 1000 m., silicate hasmophytic communities are rarer. They are almost absent in North Bulgaria; the Svistov-Suhindol fault is one of the exceptions. It has anthropogenic origin, a result of extraction of basalt. Large areas of such silicate outcrops at low altitudes are more frequent in South Bulgaria: Strandzha Mts., Sakar Mts. and especially East Rhodopi Mts. In Strandzha Mts. silicate rocks are more limited. The occurrence of Stachys angustifolia, Cheilanthes persica, Saponaria stranjensis, Sempervivum leucanthum, Silene compacta, Umbilicus horizontalis, and U. rupestris is typical.In the gorges along Arda River, near Studen Kladenets dam at Madzharovo town, there are high vertical volcanic rocks: gneiss, volcanic tuffs, riolites, etc. which have diverse hasmophytic vegetation. More specific is the participation of Alyssoides bulgarica, Anthemis rumelica, Potentilla regis-borisii, P. rupestris, Silene lerchenfeldiana, Verbascum humile, V. roripifolium, and V. rupestre. Haberlea rhododpensis forms rock coenoses with high projective cover on wet rocks. On sunny and open places Anthoxanthum aristatum, Micropyrum tenellum, Notholaena maranthae etc. make similar coenoses. The vegetation on silicate rocks is united in one Dacian-Balkan alliance Silenion lerchenfeldianae (Androsacetalia vandellii, Asplenietea trichomanis), that occurs in a very wide vertical range, from the mountain foothills (800–1000 m alt.) up to 2925 m alt. The floristic composition of the coenoses differs according to the altitude and the exposure. More detailed floristic studies may lead to the determination of additional syntaxa such as Asplenion septentrionalis and Hypno-Polypodion vulgaris (Asplenietalis septentrionalis, Asplenietea trichomanis). They encompass the vegetation from lower altitudes (the first syntaxon) and coenoses rich in mosses on shady rocks (the second syntaxon)in Central Europe.

Characteristic taxa.

Distribution in Bulgaria. In all mountains of the country, from (400) 700 up to 2925 m alt.

Conservation importance. Many vascular plants of conservation value occur in the hasmophytic communities on silicate rocks like: Alchemilla asteroantha, A. jumrukczalica, Androsace obtusifolia, Aquilegia aurea, Athyrium distentifolium, Bartsia alpina, Campanula scheuchzeri, Centaurea kernerana, Cerastium decalvans, Cheilanthes persica, Clematis alpina, Draba carinthiaca, Galium heldreichii, Gentiana acaulis, G. frigida, Jovibarba heuffelii, Potentilla regis-borisii, Ranunculus incomparabilis, Rhodiola rosea, Rhododendron myrtifolium, Saponaria stranjensis, Sempervivum leucanthum, Seseli bulgaricum, S. rhodopeum, Symphyandra wanneri, Verbascum rupestre.

Threats. Erosion, rock weathering, air pollution, direct or indirect destruction of the hasmophytic vegetation in the areas close to tourist complexes.

Conservation measures taken. The habitat is included in Annex № 1 of BDA. A significant part of its localities are within protected areas of Rila, Pirin and C Balkan National Parks, Strandzha Nature Park, different protected areas in East Rhodopi Mts. and sites from the European Ecological Network NATURA 2000.

Conservation measures needed. Study of the syntaxonomy of the hasmophytic vegetation in Bulgaria, identification of rare and endangered syntaxa and monitoring aiming at their conservation.

References. Meshinev et al. 2000; Roussakova 2000.

Authors: Veska Roussakova, Chavdar Gussev.


Silicate rocks with chasmophytic vegetation (distribution map)