06H2

H. Inland rock habitats

Mountain calcareous screes

Relationships with habitat classifications. EUNIS: H2.45 Rhodopi calcareous screes; PAL. CLASS.: 61.25 Rhodopi calcareous screes; HD 92/43: 8120 Calcareous and calk schist screes of the montane to alpine levels (Thlaspietea rotundifolii).

Conservation status. BDA, HD.

Category. Vulnerable [VU – A1, 2 B2 C1 D1 E1 F1 G1 H2 I J L1].

General characteristics. This habitat type occurs mainly in Pirin and Rhodopi Mts., more rarely in the Balkan Range and even more rarely in Rila Mts. and other mountains of Bulgaria. The North Pirin Mts. is rich in calcareous screes, located mainly on the slopes of the glacial river valleys in the subalpine belt and in the glacial cirques at high altitude in the alpine belt. The soil-forming substrate is marble or schist rich in limestone, hence the characteristics of the different habitats vary. This fact together with the dynamic stage of the different plant groups explains the existence of three local associations: Papveri degenii-Armerietum alpinae (divided in two subassociations) and Veronico kellereri-Silenetum prostratae belong to the local for Pirin Mts. alliance Veronico-Papaverion degenii. The third association, Bromo lacmonices-Geranietum macrorrhizi, is in the alliance Silenion marginatae.

The pioneer association Papveri degenii-Armerietum alpinae occurs between 2200 and 2700 m alt. on 25 to 45° steep slopes, and rarely in almost flat areas (5–10°). The exposure is mainly northern or northeastern, and more rarely western or southwestern. The substrate consists of rock pieces 10–20 cm in diameter, mixed with smaller pieces among which chernozem soil is accumulated. It retains water that sometimes appears on the slopes, from the melting snow, since in most cases the localities are in places where a thick snow layer is accumulated. As a result of this, the humidity of the habitat is good. Erosion is also often observed. Plants from different ecological groups develop in such conditions, including hasmophytes, hyonophytes, hekistotherm species from the alpine coenoses.The floristic composition of the communities, the species abundance and the total projective cover can vary, the latter between 25 and 75%. Arenaria biflora, Armeria alpina, Doronicum columnae, Draba scardica,Galium demissum subsp. stojanovii, Myosotis alpestris, Papaver degenii, Saxifraga adscendens subsp. discolor, S. androsacea, S. exarata subsp. pirinica, S. oppositifolia, Sedum atratum, Silene pusilla, Veronica kellererii, Ditrichum flexicaule, Hymenostylium recurvirostrum,and Leskea polycarpa are widely distributed. The differences in the sizes of the dominating rock pieces and the evolution stage of the soil and vegetation presuppose the existence of two subassociations. The first is the typical one, occurring on steep slopes with larger skeletal material and courser pieces, mainly in shady places, slow evolutionary processes with the participation of most of the listed species. The phytocoenoses from the second subassociation cover areas with more sunlight; the soil-formation processes are faster although the altitude is high. The characteristic species are Alyssum cuneifolium subsp. pirinicum, Dianthus microlepis, Festuca riloensis, and Pedicularis orthantha. Cerastium alpinum subsp. lanatum and Poa alpina occur more frequently. On marble and mobile screes in the alpine belt of Pirin Mts. (rarely at lower altitudes, up to 2200 m) occur the coenoses of the association Veronico kellereri-Silenetum prostratae. The screes consist of rock pieces of different size, including some with a diameter as large as 1 m. They occupy sunny, steep slopes up to 45°. The area of the separate phytocoenoses is very small, mainly between 50 and 100 m2. The floristic composition is not very rich. Silene vulgaris subsp. prostrata, a species typical for screes dominates the coenoses and Arabis ferdinandi-coburgi, Armeria alpina, Doronicum columnae, Euphrasia salisburgensis,Galium demissum subsp. stojanovii, Linum capitatum, Myosotis alpestris, M. suaveolens, Senecio rupestris,and Veronica kellererii participate. On mobile or partly fixed screes that consist of marble pieces of different sizes and slopes of less than 40°, mainly between 1800 and 2000 m alt., the coenoses dominated by Geranium macrorrhizum occur. Bromus lacmonicus, Lamium garganicum, Melica ciliata, Moehringia pendula, Teucrium chamaedrys, Thalictrum minus subsp. olympicum, Tortula intermedia etc. have a more limited distribution and abundance. The succession process leads towards Anthyllo-Seslerion klasterskii: the locality of the relic species Rheum rhaponticum is a scree of this type. It is situated on the southern slope above Kirilova Polyana locality in Rila Mts. The plants on these screes are often pulled out by strong water currents and collapsing of new rocks. Therefore the number of species is low. Very rarely, on small areas in Slavyanka, Pirin and Rhodopi Mts., between 1000 and 2000 m alt. a dominating species (mainly as assectator) on the calcareous screes is Sideritis scardica, a rare species for the Bulgarian flora and a Balkan endemic. The habitats are dry, the patches of Sideritis scardica are scattered among other herbaceous species. They also occur on calcareous rocks. Morina persica is another rare species from the Bulgarian flora that dominates on small areas in the low mountains of Bulgaria in Znepole region, South Pirin Mts., and Central Rhodopi Mts., up to 2000 m alt. It is more typical for calcareous rocky outcrops than for calcareous screes. The coenoses that develop on calcareous screes belong to class Thlaspietea rotundifolii and order Thlaspietalia rotundifolii. Its syntaxonomy at the association level has not been studied completely in Bulgaria.

Characteristic taxa.

Distribution in Bulgaria. All mountains of Bulgaria, but mostly in the high ones.

Conservation importance. Very rare phytocoenoses and species protected by the law: Alyssum stribrnyi, Arenaria pirinica, Brassica jordanoffii, Campanula cochlearifolia, Centranthus kellereri, Minuartia rhodopaea, Rheum rhaponticum Silene vulgaris subsp. prostrata, Thymus perinicus, Viola orbelica etc.. Local syntaxa also develop.

Threats. Grazing, collapsing of new rocks from above, denudation and intensive erosion process, etc. In some places the mobility of the substrate destroys the vegetation; avalanches also have negative impact. Tourism development within the borders of protected areas cause indirect and directs destruction of the screes, even high in the mountains.

Conservation measures taken. The habitat is in Annex № 1 of BDA. Part of the mountain calcareous screes are in sites of the European Ecological Network NATURA 2000 and other protected areas.

Conservation measures needed. Prohibition of grazing by domestic animals, detailed study of the specificities of the habitat; identification of priority localities for monitoring.

References. Mucina et al. 1990; Roussakova 2000; Simon 1958.

Author: Veska Roussakova


Mountain calcareous screes (distribution map)