21C3
Muddy river banks with semi-ruderal communities of tall, annual hygrophytes
Relationships with habitat classifications. EUNIS: C3.53 Euro-Siberian annual river mud communities; PAL. CLASS.: 22.52 Euro-Siberian annual river mud communities; HD 92/43: 3270 Rivers with muddy banks with Chenopodion rubri p.p. and Bidention p.p. vegetation.
Conservation status. BDA, BC, HD.
Category. Endangered [EN – A1, 2 C2 D2 E2 F2 G2 H2 J].
General characteristics. The habitat encompasses muddy river banks of large rivers in the lowlands, where tall annual (0,50–0,70 m high), pioneer nitrophilic (ruderal) plant communities develop. They belong to the alliances Bidention and Chenopodion rubri of class Bidentetea tripartiti. The communities are related and develop after the water retreats leaving behind mud that is rich in organic material and nitrogen. They usually appear at the end of the summer, while early on, the banks are muddy and without vegetation. If the conditions are not suitable, for instance as a result of autumn rains that make the water level high, it is possible that this vegetation develops to a limited extent or does not develop at all within the vegetation season. This habitat is typical for the lower parts of the valleys of large rivers – the Danube, Maritsa, Iskar, Yantra, Toundzha rivers. The nitrophilic species prevail in the species composition which is dominated by Bidens frondosa, B. tripartita, Persicaria hydropiper, P. lapathifolia, Rumex conglomeratus, and Xanthium italicum.These communities usually make complexes with the communities of the small annual hygrophytes (see “Muddy and sandy river banks with communities of small, annual hygrophytes”), although the projective cover of the first group is higher. Species that are more typical for the habitat of the small, annual hygrophytes occur also in the composition of these ruderalized coenoses. Such are mainly Cyperus glomeratus, C. fuscus, Dichostylis michelianus (= Cyperus michelianus), Echinochloa crus-galli,and many others. In some places, at the end of the vegetation season, the semi-ruderal coenoses can be replaced by pioneer hygrophytic coenoses that represent a later succession stage of the vegetation on the banks where the water has retreated.
Characteristic taxa.
- Vascular plants: Artemisia annua, Bidens cernua, B. frondosa, B. tripartita, Catabrosa aquatica, Chenopodium ambrosioides, C. glaucum, C. rubrum, Cyperus strigosus, Echinochloa crus-galli, Lythrum salicaria, Myosoton aquaticum, Persicaria hydropiper, P. lapathifolia, P. mitis, Polygonum aviculare, Potentilla supina, Ranunculus sceleratus, Rumex conglomeratus, R. maritimus, R. palustris, Veronica anagallis-aquatica, Xanthium italicum.
- Fungi: Macromycetes – Agaricus subperonatus, Peziza echinospora; Micromycetes – Ascochyta vollubilis, Erysiphe betae, Septoria polygonorum (on Persicaria hydropiper), Podosphaera xanthii, Puccinia xanthii (on Xanthium italicum); Uromyces rumicis (on Rumex palustris).
- Animals: Lycaena dispar, Actitis hypoleucos, Charadrius dubius.
Distribution in Bulgaria. Along the Danube, and its islands; along Maritsa, Toundzha, Vit, Iskar, Yantra and Ogosta rivers.
Conservation importance. Some rare and protected species such as Dichostylis michelianus (= Cyperus michelianus) occur on the alluvial riverbanks.
Threats. Extraction of gravel and sand from the river terraces, changes in the hydrological regime of the rivers: draining, redirection of the river beds, invasion of alien species (neophytes that replace the populations of the autochthonous species and change the typical species structure of the coenoses), erosion, low water levels, floods along the river valleys.
Conservation measures taken. The habitat is in № 1 of BDA. Some of the localities are within protected areas – Persina Nature Park, Kalimok-Brashlen Protected Site, Konplex “Aleko-Telika” Protected Site, Ibisha Managed Nature Reserve, and sites from the European Ecological Network NATURA 2000.
Conservation measures needed. Study of the dynamics and threats of this habitat type, particularly in areas of massive distribution of invasive species (e.g. along the Danube). Termination of hydro-ameliorative activities and extraction of gravel and sand along rivers (mainly the Danube) in the sites from NATURA 2000.
References. Kolev 1964; Tzonev 2002.
Author: Rossen Tzonev
