F. Shrub communities

Alpine calciphilic dwarf-shrub communities near melting snow-patches

Relationships with habitat classifications. EUNIS: F2.1211 Alpine espalier willow snow communities; PAL. CLASS.: 36.12211 Alpine Salix retusa-reticulata snow patches; Bondev (1991): 2 Calciphilous, cryophytous grass (Kobresieta myosuroides, Cariceta kitaibelianae, Seslerieta korabensis, etc.) and dwarf shrub communities (Dryeta octopetalae, Saliceta reticulatae, etc.).

Conservation status. None.

Category. Critically endangered [CR – B1 C3 D3 E3 H3 I J].

General characteristics. The phytocoenoses of the dwarf willows in the vegetation of the alpine belts in the Bulgarian mountains are the remains of a cover which existed in Bulgaria during the last glaciation period in Europe. They occur very rarely and on small areas mostly linked to snow drifts. Such habitats are very specific. The snow melting continues till the beginning of the summer, and in some places the snow remains during the whole summer. The big snow mass presses the plants and restricts their growth, and the vegetation period is delayed and shortened. Most often it is not longer than 2–3 months. Therefore, the plant and soil development is also strongly delayed. In such places the soils are shallow, subjected to erosion. The fine soil particles accumulated between the stones (mostly small ones, rarely of medium-size) retain humidity that comes from the slowly melting snow and rains and hence the humidity is high throughout the summers. The temperature is lower than in the surrounding places and its amplitude is small. The slant and exposure of the slopes vary considerably. The slightly slanting slopes with northern exposure prevail, but there are also very steep slopes with southern exposure. The soil profile hardly reaches 5–10 cm, the presence of the skeletal material is high, often with numerous small stones on the surface. The soil formation on alkaline basic rocks results in alkaline soil solutions. Among the dwarf willows, Salix reticulata occurs more often, while S. retusa that develops on silicate bedrock has very limited distribution in Bulgaria. Salix reticulata is a procumbent small shrub with strongly branched ground stem and rooting shoots. In Pirin Mts. it prefers habitats protected from the direct sun, e.g. in slightly concave relief forms on rocky slopes or stony screes of calcareous schists or marble in the alpine belt where much snow accumulates. Salix reticulata has the well-expressed features of an edificator that strongly dominates over the remaining species in the phytocoenoses. The total projective cover of the communities is high, 80–100%. Most of the plants are small, caespitose and adherent to the ground. The following species occur more often: Bartsia alpina, Bistorta vivipara (= Polygonum viviparum), Erigeron uniflorus subsp. vichrensis (= Erigeron vichrensis), Pedicularis verticillata, Primula minima, Saxifraga androsacea, S. ferdinandi-coburgi, S. oppositifolia, Veronica kellererii, etc. Relatively tall plants like Armeria alpina, Carex kitaibeliana, C. parviflora, Poa pirinica, Primula halleri, and Sesleria coerulans occur more rarely and do not form a separate layer. All phytocoenoses belong to the association Bartsio-Salicetum reticulatae. These are among the phytocoenoses that are richest in rare species, including local endemics, in the vegetation cover of Bulgaria. For instance the local endemic Erigeron vichrenensis has its phytocoenological optimum here. The soil surface is covered by different moss species: Hymenostylium recurvirostrum, Mnium stellare, Polytrichum juniperinum, Tortella tortuosa, etc.

The phytocoenoses of Salix reticulata in Rila Mts. have very limited distribution. They are localized mainly in the region of the Rilets ridge and cover not more than 100 m2. In some places the slope can reach 30°, rarely more. The exposure is mostly northern. The most significant difference between the phytocoenoses in Rila and Pirin Mts is that in Rila Mts the distribution of typical chionophilic species different from the edificator is very limited. Species like Seslerietalia bielzi (Armeria alpina, Galium anisophyllon, Myosotis alpestris, Saxifraga adscendens subsp. discolor, S. exarata, Silene acaulis) are well represented. They are followed by species from the neighbouring alpine herbaceous phytocoenoses on acidic substrate: Seslerietalia comosae (Avenula versicolor, Carex curvula, Dianthus microlepis, Festuca airoides, F. riloensis, Poa media, Sesleria comosa ets.). In one of the already described phytocoenoses the abundance of Salix reticulata is similar to this of Salix retusa. So far, Salix retusa has been found only in Rila Mts., where it occurs on the ridge of Ibar peak. The species is slightly more frequent on the Rilets ridge where several isolated localities have been registered. Apart from growing together with Salix reticulata the species is represented by several pure groups of individuals. The associations related to this habitat type belong to order Arabidetalia caeruleae of class Thlaspietea roundifolii.

Characteristic taxa.

Distribution in Bulgaria. The alpine belt of Rila and Pirin Mts., above 2500 m alt.

Conservation importance. Rare phytocoenoses in the vegetation cover of Bulgaria with rare and protected species: Armeria alpina, Carex parviflora, Erigeron uniflorus subsp. vichrensis (= Erigeron vichrensis), Galium demissum subsp. stojanovii, Gentiana punctata, Poa pirinica, Primula halleri, Salix retusa, Saxifraga adscendens subsp. discolor, S. androsacea, S. exarata, S. ferdinandi-coburgi, S. oppositifolia, etc.

Threats. Intensive tourism and its negative impacts: trampling, pollution, picking of flowers, etc.

Conservation measures taken. The localities of this habitat are within Rila and Pirin National Parks and in sites of the European Ecological Network NATURA 2000 in Bulgaria.

Conservation measures needed. Monitoring of the habitat and effective implementation of the legal acts related to the management of protected areas.

References. Mucina et al. 1990; Rodwell et al. 2002; Roussakova 1995, 2000.

Author: Veska Roussakova

Alpine calciphilic dwarf-shrub communities near melting snow-patches (distribution map)