A24 - Juncus Bulbosus Community

Summary

Synonymy

Peaty moorland lochs West 1910 p.p.; Juncus fluitans consocies Pearsall 1921; Juncus fluitans vegetation Pearsall 1921; Juncus fluitans-Utricularia sociation Spence 1964; Juncus fluitans-Sphagnum subsecundum sociation Spence 1964; Sphagno-Sparganietum angustifolii Tüxen 1937 sensu Schoof-van Pelt 1973 p.p.; Scorpidio-Utricularietum Muller & Gors 1960 sensu Birse 1984 p.p..

Constant species

Juncus bulbosus.

Rare species

Utricularia intermedia.

Physiognomy

Juncus bulbosus is a plant of quite high frequency and some local abundance in a variety of aquatic communities and swamps, but in the vegetation included here it tends to be the most prominent feature along with a range of rather distinctive associates. Stands of this Juncus bulbosus community are of varying cover and luxuriance, with J. bulbosus itself occurring in the forms commonly recorded as var. fluitans, with branches procumbent and rooting at the nodes, or in free-floating masses, often forming dense tangles.

Occasionally, stands have very little else apart from J. bulbosus and no other species occurs frequently throughout the community, but Potamogeton polygonifolius is fairly common, sometimes with quite an extensive cover of floating leaves, particularly in shallower peaty waters, and some stands, often at greater depth and on rather more silty substrates, have P. natans. Then, Scirpus fluitans may be found, frequently hard to see among the floating rush shoots, and there can be some Callitriche hamulata or C. stagnalis. Myriophyllum alterniflorum is characteristic of one kind of Juncus vegetation and may be accompanied by occasional Potamogeton obtusifolius, P. gramineus and P. berchtoldii, though these are not usually present at very high covers.

More striking is the occurrence of various Utricularia and Sparganium spp. Commonest among the former is what has generally been recorded as U. vulgaris, but what is more likely to be the less basiphilous taxon in this aggregate, U. neglecta (Perring 1968). This is very hard to separate from U. vulgaris sensu stricto, especially with vegetative material which is all that has been found in the northern part of Britain where this vegetation is most common. U. minor has also been seen in this community and, very rarely, U. intermedia, although much care needs to be taken to distinguish this from U. ochroleuca.