A perennial herb found on ungrazed faces and ledges of wet or dry calcareous cliffs. It grows in short vegetation or amongst tall herbs, or in dwarf Salix scrub. Populations are probably maintained by vegetative growth. From 550 m in Coire Ghamhnain (Main Argyll) and usually above 700 m, reaching 1095 m on Ben Lawers (Mid Perth).
The distribution of C. atrata is stable.
Circumpolar Boreo-arctic Montane element.
Light (Ellenberg): 7
Moisture (Ellenberg): 5
Reaction (Ellenberg): 6
Nitrogen (Ellenberg): 3
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): -0.3
July Mean Temperature (Celsius): 11.1
Annual Precipitation (mm): 1980
Height (cm): 50
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 57
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.02
Scarce Atlas Account
Carex atrata L.
A strictly montane plant, C. atrata grows on ungrazed faces and ledges of calcareous cliffs of the higher mountains, as scattered tufts or small clumps in both dry and moist places. Typical associates are other montane calcicoles, such as Carex capillaris, Cerastium alpinum, Dryas octopetala, Persicaria vivipara, Poa alpina, Saxifraga aizoides, S. nivalis, S. oppositifolia, Silene acaulis and Thalictrum alpinum; and more widespread plants such as Carex flacca, Festuca ovina agg. and Thymus polytrichus. On more stable ledges with taller herbaceous communities, it grows with Angelica sylvestris, Geum rivale, Oxyria digyna, Saussurea alpina, Sedum rosea and Trollius europaeus. C. atrata also occurs amongst open growths of Salix lapponum and other montane willows. The attitudinal range is from 550 metres at Coire Ghamhnain in Glen Orchy to 1060 metres on Beinn Heasgarnich.
A perennial, C. atrata flowers and produces ripe fruits in most localities, but there is no information on germination. Probably most populations are maintained by vegetative growth, and this species appears to have little capacity for spread under present conditions, although this may be mainly a grazing limitation.
South of the Scottish Highlands, the best population is on Snowdon, and it is very rare elsewhere. It is almost plentiful on the Breadalbane mountains, but is nowhere abundant. It may once have had a wider distribution at high levels, and if so it has evidently become restricted to steep rock habitats through grazing. It is probably still present in most of the 10 km squares for which only pre-1970 records are available.
This is a circumpolar arctic-alpine species, occurring in the high mountain systems of central Europe, Asia and the Rockies, as well as widely at higher latitudes. In southern Norway it grows in open birchwood and willow scrub as well as in montane herbaceous and rock communities, while in Norwegian Lapland it grows down to sea level in closed herb-rich grassland.
D. A. Ratcliffe
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1982. Sedges of the British Isles. Botanical Society of the British Isles Handbook no. 1, edn 2.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
1994. Scarce plants in Britain.