Amberley Wild Brooks and Arun Valley IPA
Location: South of Pulborough, West Sussex. North of B2139.
Grid Reference: TQ 039 161
The Arun valley comprises an associated set of wetland habitats with adjacent chalk and sandy grassland.
Although Amberley Wild Brooks, a site well-known for its outstanding aquatic flora, is a key feature, other areas such as Pulborough Brooks and unimproved pastures and sandy grassland near Watersfield are of great value.
The Arun Valley floodplain consists of a complex of meadows and drainage ditches, with a diverse flora including species of brackish, calcareous and acidic waters. The valley as a whole contains the vast majority of the native UK population of cut-grass, a plant which is restricted to ten UK locations, together with nationally important populations of true fox-sedge, sharp-leaved pondweed and narrow-leaved water-dropwort (the main colonies of the latter being outside Amberley Wild Brooks).
Amberley Wild Brooks is an extensive area of grazing marsh which is dissected by drainage ditches. The wettest parts of the marsh are dominated by soft rush, sedges and tussock grass. Drier fields, particularly in the south, have meadow grasses, crested dog’s tail grass and rye grass.
Species of note from the wettest grazing marsh include fen orchid, true fox sedge and marsh cinquefoil. The ditches which dissect the grazing marsh support 156 species of flowering plant. In addition to the rare cut grass the flora includes all five British duckweeds, all three British water-milfoils, all five British watercresses, all but one of the seven British water dropworts, and two-thirds of the British pondweeds including the uncommon sharp-leaved pondweed.
Other notable plants include greater water-parsnip, small water pepper, greater bladderwort, frogbit and flowering rush, also the marsh fern is an uncommon plant which occurs here.
Pulborough Brooks has been managed for centuries as flood meadows which are cattle grazed and cut for hay during the summer. Most fields consist of species-poor rough damp pasture. The ditches are locally of great botanical importance, supporting populations of the nationally rare sharp-leaved pondweed and many other characteristic species including frogbit, arrowhead, flowering rush, hairlike pondweed, fine-leaved water dropwort and greater water parsnip. The nationally scarce narrow-leaved water dropwort and small water pepper also occur.