Distribution patterns, floristic structure and habitat requirements of the alpine river plant community Stuckenietum amblyphyllae ass. nova (Potametea) in the Pamir Alai Mountains (Tajikistan)

This paper discusses the floristic structure, distribution and habitat requirements of a new aquatic syntaxon, Stuckenietum amblyphyllae ass. nova. Patches of the Stuckenietum amblyphyllae association occur in the Pamir Alai Mountains in Middle Asia (Tajikistan). The biotope of this community represent high mountain rivers and ponds at the bottom of glacial river valleys situ- ated at elevations between 1900 and 3800 m. Patches of the Stuckenietum amblyphyllae association are characterised by a clear predominance of the typical species, i.e. Stuckenia amblyphylla, which occupies an aerial extent of between near 40 up to 90% of the surface studied. Patches of the community are poor in species, comprising a maximum of five taxa. Among associated species mainly rush, aquatic, meadow and marsh taxa have been noted. The Stuckenietum amblyphyllae community prefers cold, open, alkaline waters with medium flow-rate, ranging in depth from 15 to 75 cm. It is also, but rarely, found in the mountain ponds. Together with the Stuckenia filiformis community it designates in the Pamir Alai Mountains the upper limit of aquatic vegetation.