Area: 53.93 (ha)
Description and Reasons for Notification:
This site is special for its population of rare and scarce bryophytes (mosses and liverworts) which are adapted to growing on copper-rich substrates. The site is made up of seven areas of formerly mined land and the lower plant interest is primarily found on the spoil tips containing copper-rich waste, although some of the areas have derelict mine buildings and other structures which also support important bryophytes.
Nationally rare species include the liverworts ‘threadwort’ Cephaloziella nicholsonii, C.integerrima, C. massalongi and the moss Scopelophila cataractae. The composite site supports over 20% of all known British populations of these four species, C. integerrima has been confirmed at only two other sites in the British Isles since 1950 and C. nicholsonii is a British endemic.
At West Basset Stamps the nationally rare bryophytes C. nicholsonii, C . integerrima, C. massalongi and Pohlia andalusica occur. In addition, the nationally scarce liverwort C. stellulifera and the mosses Bryum pallescens and Gymnostomum viridulum are also present, the last being at its only locality in Britain where the species occurs with capsules.
The Dolcoath Road site supports the rare C. nicholsonii, C. integerrima, C. calyculata, P. andalusica and the scarce C. stellulifera. C. calyculata occurs on the tops and sides of two of the old wheel pit walls here.
The spoil tips, stream side and leat associated with the Tolgus Tin Works support C. nicholsonii, C. massalongi, C. integerrima, S. cataractae and P. andalusica, the latter being at its only site in Britain at which capsules have been recorded. Except for S. cataractae, the open areas of the mine spoil tips on the eastern side of Porkellis Moor support the same species.
At Poldice Valley the spoil tips and old mining structures support extensive areas of C. nicholsonii, P. andalusica, C. stellulifera and the nationally scarce moss B. donianum.
The land to the east of Godolphin Bridge supports C. massalongi, P . andalusica, and S. cataractae as well as B. donianum, C. stellulifera andFossombronia caespitiformis.
The locations of particularly high interest for bryophytes within each area are those having very high levels of copper. As a result of the toxic nature of the spoil tips these locations support little more than a mat of low-growing bryophytes and, in some places, lichens. These occupy relatively small areas within a more generally scrubby vegetation, with European gorse Ulex europaeus, willows Salix sp, heather Callunavulgaris or rank grassland. Although the growth of these invasive species is slow due to the toxic nature of the spoil tips, in the long term the sites will require active management to prevent them shading out or growing over the areas that are important for bryophytes. Where the structures and old buildings support important bryophytes then care must be taken during preservation or derelict land operations to safeguard the specialised conditions the plants require.