C. Inland waters

Vegetation of oligotrophic, fast-flowing mountain streams and rivers

Relationships with habitat classifications. EUNIS: C2.25 Acid oligotrophic vegetation of fast-flowing streams, C2.26 Lime-rich oligotrophic vegetation of fast-flowing streams. Pal. Class.: 24.41 Acid oligotrophic river vegetation, 24.42 Lime-rich oligotrophic vegetation; HD 92/43: 3260 Water courses of plain to montane levels with the Ranunculion fluitantis and Callitricho-Batrachion vegetation.

Conservation status. BDA, HD.

Category. Vulnerable [VU – A1, 2 B1 C1 D2 E1 F2 G2 H2 I J L3].

General characteristics. This habitat type encompasses parts of the upper flow of mountain streams and rivers that occur above 800–1200 m alt. with the speed of water above 1 m/s. The plant communities develop in the beds of the mountain streams and rivers mainly from 1200 up to 2500 m alt. The temperature of the water is low throughout the year. The bottom and banks are rocky or stony (stones are of different size), very rarely with sand-gravel or clay deposits. The water flow is almost always fast, the water is pure and poor in nutrients. The acidity is most often close to the neutral value. The water quantities show a clear spring maximum and autumn-winter minimum. This regularity is particularly typical for the karst areas in North Pirin, West and Central Balkan Range, and Rhodopi Mts. During the minimum period sometimes the surface water flow is absent (so called “lost waters”). This phenomenon can occur often in summers as well and can cause the absence of plants and animals in the midstream of the water bodies. The oxygen content is high, and the physical aeration prevails. The water turbulence is very strong as a rule and the stones and the rocky bottom in the riverbeds are smooth. Therefore the attachment of the plants is very difficult and most often impossible. The abrupt increase of the water quantity that is typical for the spring snow melting, although very short, increases the erosion-accumulation processes and additionally leads to the eradication and destruction of the plants. Some specific plants survive in these utterly unfavourable conditions: the mosses have greater chance to persist and develop. Their phytocoenoses are of different sizes, mainly very small and close to the banks where the water current is slower. The main edificators are Fontinalis antipyretica and Calliergon cordifolium.

Vascular plants very rarely occur on silicate rocks, mainly Cardamine amara, and at lower altitudes – also Alisma plantago-aquatica, A. lanceolatum,etc. The vascular plants Sparganium angustifolium, Ranunculus aquatilis, and more rarely Subularia aquatica occur (sometimes with high abundance) in the areas of waterflows out from the glacial lakes, where the slope is more moderate and there is a biological drift of plankton limnobionts and benthic reobionts. In karst mountain areas, where the autumn-winter minimum is more clearly expressed, the phytocoenoses consist of Leptodictyum riparium, Hygroamblystegium tenax, Calliergon cordifolium, Cinclidotus aquaticus, C. fontinaloides, C. riparius, Conocephalum conicum, Fissidens crassipes, Fontinalis antipyretica, Rhynichostegium riparioides, Scapania compacta, S. undulate,etc. The flowering plants are few. The species composition is identical to the one of the water streams on silicate rocks.

Characteristic taxa.

Distribution in Bulgaria. All mountains of Bulgaria, above 800–1000 m alt.

Conservation importance. Regulation and maintenance of the water flow in the rivers and streams in the country, maintenance of the underground waters and the humidity of the surrounding terrestrial ecosystems; the habitat for rare and endangered plants and animals.

Threats. Tourism and tourist infrastructure, pollution with organic and other types of waste, hydro-construction activities, mountain stock breeding, deforestation in the area of the water catchments, hence increased erosion, etc.

Conservation measures taken. The habitat is in Annex № 1 of BDA. A significant part of it is within protected areas – Rila, Pirin and Central Balkan National Parks, Vitosha Nature Park and sites from the European Ecological Network NATURA 2000.

Conservation measures needed. Limitation of the tourist flow in the areas of the vulnerable water bodies. Prohibition of the construction of ski tracks near the mountain streams and rivers. Control of the water quantities that will be used for household and industrial purposes.

References. Kovachev 2000; Kozuharov 2006; Stoichev 1996; Vannote et al. 1980; Videnova et al. 2000.

Authors: Jordan Uzunov, Dimitar Kozhuharov, Anna Ganeva, Veska Roussakova

Vegetation of oligotrophic, fast flowing mountain streams and rivers (distribution map)