Portholme

Also within

Cambridgeshire County

Condition (Natural England)

Habitats

Fast flowing river and stream

Geology & landscape

Landscape processes: Fluvial

Description

Description This area holds grassland communities of the alluvial flood meadow type. Portholme represents one of the largest areas of this grassland type in the country which continues to be managed on traditional linesas a ‘lammas’ meadow. Watercourses on the periphery of the site have populations of some uncommon invertebrates, including one dragonfly which is of a nationally restricted distribution. The grassland communities are characterised by the presence of such grasses as Yorkshire fog Holcus lanatus, yellow oat grass Trisetum flavescens, meadow foxtail Alopecurus pratensis and meadow fescue Schedonorus pratensis. The range of herbs present, typical of such meadows, includes lady’s bedstraw Galium verum, pepper saxifrage Silaum silaus and great burnet Sanguisorba officinalis. A number of locally rare and one nationally rare plant are also present. The meadow is surrounded by channels of the River Ouse and the Alconbury Brook is close by. These water bodies are important for dragonflies Odonata in particular the restricted dragonfly Libellula fulva. The traditional management of this site, which still continues, is by cutting for hay followed by grazing of the aftermath in later summer until the autumn. In winter and early spring Portholme is inundated by flood waters. This provides natural fertilising of the soil and it is this seasonal flooding coupled with the traditional management that maintains the diversity of the natural plant communities.

Species mentioned

Plant communities