Studies on the Ecology of Rivers: I. On the Distribution of Macrophytic Vegetation in the Rivers of Britain

Abstract

The macrophytic vegetation of 9 English rivers is described, viz.: New Forest streams, Leven (Lanes.), Mole (Surrey), Tees (Durham-Yorks.), Wharfe (Yorks.), Tern (Shrops.), Dove (Derby), Itchen (Hamps.), Lark (Suff.). The chief habitat factors are rapidity and variability of current resulting in differences in silting of the bed, and calcareous content of the water. Four types of habitat are distinguished: Torrential, characterised by mossy vegetation of Eur-hynchium and Fontinalis (in calc.-water) ; nonsilted, with Ranunculus fluitans and Myriophyllum spicatum; partly silted, with Potamogeton polygonijolius (in non-calc. water), P. perjoliatus, and Sparganium simplex; silted, with Juncus supinus (in non. calc), Callitriche stagnalis, Elodea, arid P. crispus; and littoral region, with Sparganium erectum. The plant communities are impermanent, and tend to shift down-stream. In some cases the vegetation dies down in winter and in others not. It is affected by sewage pollution and excessive deposition of silt, and itself affects the rate of current-flow and silt-deposition.