Carex ferruginea

Carex ferruginea, the rusty sedge or rust-coloured sedge, is a species of flowering plant in the family Cyperaceae.^[2][3] It is native to the Alps, the southern Carpathians, and the western Balkan Peninsula, and has been introduced to the U.S. state of New Jersey.^[1] It is a glacial relict species.^[4]

This species is a part of the distinctive grassland communities along the alpine chain. A phytosociological survey of the south-eastern Alps described the new ecological association Hormino pyrenaici–Caricetum ferrugineae, highlighting the independence of this flora from that of the northern Alps.^[5]

The species ranges throughout the entire Alpine arc, the Jura, the southern Carpathians and parts of the Balkan Peninsula.^[5]

It occupies the subalpine belt at roughly 1700–2300 metres elevation, where it builds dense, sloping meadows in sites with a constant groundwater supply—either from shallow aquifers in depressions or from the slow melt of long-lasting snow beds. On steep, freely draining slopes the prolonged snow-melt is vital for retaining soil moisture.^[5]

South-eastern Alpine stands differ floristically from their northern counterparts. Diagnostic companions include the dragon's-mouth Horminum pyrenaicum, Pedicularis elongata, Potentilla crantzii, Scorzonera aristata, Knautia longifolia and Festuca norica.^[5]

The meadows are dominated by C. ferruginea with frequent Carex sempervirens, Sesleria varia, Deschampsia cespitosa and F. norica beneath a conspicuous layer of flowering herbs such as Trollius europaeus, Leontodon hispidus and Veratrum album.^[5]

The association is recorded from the Val d'Adige (Bolzano) eastwards to at least the Canal del Ferro (Udine), with probable extensions into the Insubrian Alps and the Alpine foothills.^[5] Four sub-associations are recognised:^[5]

• typicum – the modal form richest in characteristic species;
• valerianetosum montanae – on relatively steep slopes in clearings of spruce woods;
• willemetetosum stipitatae – in gently sloping depressions adjoining neutro-alkaline fens;
• ericetosum carneae – the driest expression, usually at the foot of stabilised scree cones.^[5]

Because these grasslands rely on very specific geomorphological, edaphic and microclimatic settings, they tend to be long-lived landscape features. Their phytogeographical distinctness underlines the autonomy of the south-eastern Alpine flora from both the northern Alpine Caricetum ferrugineae and the Illyrian Hyperico alpini–Caricetum ferrugineae communities.^[5]