W5 - Alnus Glutinosa-Carex Paniculata Woodland

Summary

Synonymy

Swamp carr Pallis 1911; Alder thicket Rankin 1911 b p.p.; Valley fen woods Farrow 1915; Alder wood Clapham 1940; Swamp carr and semi-swamp carr Lambert 1951; Alder woodland types 2c p.p. & 3c McVean 1956b; Alder carr Sinker 1962; Valley fen alderwoods Haslam 1965; Osmundo-Alnetum glutinosae (Klötzli 1970) Wheeler 1980c p.p.; Alnus-Salix woodland XXiii Meres Report 1980; Alder stand types 7Ba and 7Bb Peterken 1981; Scutellaria galericulata-Alnus glutinosa Association Birse 1982 p.p.; Woodland plot type 14 Bunce 1982 p.p.

Constant species

Alnus glutinosa, Carex paniculata, Galium palustre, Rubus fruticosus agg., Brachythecium rutabulum, Eurhynchium praelongum.

Rare species

Carex appropinquata, C. elongata, Cicuta virosa, Dryopteris cristata, Peucedanumpalustre, Thelypterispalustris.

Physiognomy

The canopy of the Alnus glutinosa-Carex paniculata woodland is characterised by the high frequency and often the great abundance of Alnus but its detailed floristics and physiognomy vary considerably according to the age of the stand and the nature of the substrate. Alnus and Salix cinerea are the most frequent invaders of the kinds of swamp and fen from which this woodland is derived and, in the early stages of colonisation, their proportions are very much a reflection of the chance availability of propagules and the frequency and disposition of sites where seedlings can gain a hold, very often here the tops and sides of Carex paniculata tussocks. In general, though, young stands are characterised by the co-dominance of these two species in low, uneven and open canopies and the general trend with ageing is for S. cinerea to be relegated to an understorey or, where the Alnus grows up to cast a deep shade, to be completely extinguished. Betula pubescens can also appear early in invasion but it is decidedly patchy and its overall frequency is no more than occasional. Once the canopy has thickened up, light quickly becomes insufficient for its establishment. In drier situations, on initially firmer substrates or in sites where the fen mat consolidates with the passage of time, Fraxinus excelsior can become frequent but it generally makes no more than a local contribution to the canopy. Quercus robur can also occur in such situations though it remains rare through the community as a whole.