01F2

F. Shrub communities

Alpine acidophilic Dwarf willow (Salix herbacea) communities

Relationships with habitat classifications. EUNIS: F2.111 Alpine acid Dwarf willow snow-patch communities; PAL. CLASS.: 36.1112 Alpine acid Dwarf willow snow-patch communities; HD 92/43: 6150 Siliceous alpine and boreal grasslands; Bondev (1991): 1 Acidophilous and psychrophilous grass (Cariceta curvulae, Festuceta riloensis, Seslerieta comosae, Junceta trifidi, Festuceta airoides, Agrostideta rupestris, etc.) and dwarf shrub communities (Saliceta herbaceae, Saliceta retusae, Empetreta nigrae, Vaccinieta uliginosi, etc.).

Conservation status. BDA, HD.

Category. Endangered [EN – A1, 2 B1 C2 D3 E2 H3 I J].

General characteristics. Salix herbacea is the smallest in size willow species – its shrubs are often several, even 1 cm high. The stems of this circumpolar (arctic-alpine) evergreen species creep on the ground. The phytocoenoses of Salix herbacea in Bulgaria are distributed in the whole alpine belt of Rila Mts and only in some places in Pirin Mts. Some phytocoenoses (on very small areas) have been established at 2000 m alt. but the optimal height for this communities is about and above 2500 m alt. Being a meso-hygrophyte this evergreen, frigophilic dwarf shrub (more a hekistothermic than a microtermic plant) occurs in some of the most extreme habitats in the upper parts of the mountains in Bulgaria, where the snow accumulates in big quantities and persists until late summer, sometimes until the new snow. The vegetative period is short, 1–2 (4) months. The habitats are of pioneer type and are characterised by very low annual temperature with small amplitude. They are localized in very variously sized lower places on the high peaks and ridges, on the northern slopes, in the glacial cirques, on silicate. The places covered by the herbaceous willow are most often of northern exposure and more rarely with northeastern or eastern exposure. At very high altitudes, they can occupy places with southern exposure as well. They are subjected to strong northern and northwestern winds. The herbaceous willow dominates the phytocoenoses on the slopes or the bottom of the cirques, in slight depressions of the relief. The areas are flat, with slight to moderate tilt that rarely reaches 50°. The Umbric Leptosols are shallow – 0,5 cm thick, rarely deeper. They are subjected to constant erosion. Small stones cover up to 30–40% of the surface. Sometimes Salix herbacea finds very favourable conditions on stony, slightly tilted bottoms of springs and even more rarely in bogs where much snow accumulates. The area of the phytocoenoses dominated by this species is usually small, several square meters to several tens of square meters, very rarely reaching several hundreds of square meters. The herbaceous willow is a glacial relic in the Bulgarian flora. It forms coenoses with other glacial or boreal relics, alpine species and regional endemics. All plants are small, many of them pressed to the soil by the snow. The herbaceous willow is an edificator whose biology makes it possible to cover a considerable part of the habitat surface. The floristic composition is poor. At more advanced stages of the development of the community more herbaceous plants participate and 2–3 layers can be identified. Alopecurus riloensis, Carex curvula, Festuca riloensis, Juncus trifidus, Sesleria comosa form a relatively high herbaceous layer, but in most of the phytocoenoses it is poorly developed. The second layer is richer in species and has a higher projective cover. The following species participate: Dianthus microlepris, Gnaphalium supinum (= Omalotheca supina), Primula minima, Salix herbacea, Taraxacum spp., etc. Mosses and lichens form the third layer and are obligate for most of the phytocoenoses.

Phytocoenoses of the herbaceous willow with Vaccinium uliginosum in bogs and springs are rare. Most of the phytocoenoses belong to the association Primulo minimae-Salicetum herbaceae. Characteristic species of this association are Salix herbacea, Primula minima, and Dianthus microlepis. Two subassociations have been identified. The typical subassociation is localized mostly on the mountain summits and their ridges and slopes and more rarely are in the large cirques. Apart from the herbaceous willow Campanula alpina, Carex curvula, Cetraria islandica, Festuca riloensis, Primula minima, and Sesleria comosa also occur. The average projective cover is 70%. On the slopes and the bottoms of the cirques the snow-drifts remain longer, the soil humidity is higher and the influence of the winds is weaker. The abundance of Carex pyrenaica, Poa media, Taraxacum spp., Ranunculus crenatus, Arenaria biflora, Alopecurus gerardii, A. riloensis, etc. increase in such localities. The average projective cover is 80%. This group of phytocoenoses belong to the subassociation Primulo minimae-Salicetum herbaceae poetosum mediae.

Characteristic taxa.

Distribution in Bulgaria. Rila and Pirin Mts; (2000) 2500–2900 m alt.

Conservation importance. Some of the very representative pioneer, chionophilic habitats on the Balkans. They shelter arctic-boreal vegetation with distinct regional specificity and include rare and endangered species: Sibbaldia procumbens, Taraxacum bithynicum, etc.

Threats. Grazing, trampling, climate changes.

Conservation measures taken. The habitat is included in Annex 1 of BDA. The localities are within the borders of Rila and Pirin National Parks and in site of the European Ecological Network NATURA 2000.

Conservation measures needed. Monitoring and limitation of the anthropogenic pressure; strict application of the restriction regimes according to the national legislation and the management plans of the national parks.

References. Ganchev 1963; Roussakova 2000.

Author: Veska Roussakova


Alpine acidophilic Dwarf willow (Salix herbacea) communities (distribution map)