Life span

Perennial, moderately long-lived.

Growth form

Solitary herb growing in small, very dense tussocks with a compact caudex. Leaves in dense clusters from caudex. Leaf bases with abundant, brown, narrowly lanceolate, acute or apiculate, dentate scales.

Leaf

Leaves 1.5–3 cm, with a short petiole 0.3–0.5 cm, less than 1/5 of leaf length. Petiole jointed (with a distinct ring, however, often hidden by scales), breaking off in the joint when the leaf is shed and leaving stiff stumps on the caudex (a character of the genus Woodsia). Blades 0.3–0.5 cm broad, narrowly oblong or linear in outline, pinnate with 8–15 pairs of pinnae. Pinnae very small, ca. 2 × 2 mm, as broad as long, moderately dissected with obtuse lobes. Petiole, rhachis and pinnae glabrous (but see Reproductive organs below), a character distinguishing W. glabella from other North Atlantic Woodsia.

Inflorescence and Flower

Reproductive organs

Sori orbicular, on lower surface of pinnae, up to 12 per pinnae as a rim along the margin, covered by persistent indusia with brownish hairs (a character for the genus Woodsia, sometimes mistaken for hairs on the blade). Each sorus has 5–10(12) sporangia. Spores pale brown, reticulate.

Fruit

Reproduction

Sexual reproduction by spores; no vegetative reproduction. Developing sporangia have been observed in several Svalbard plants but no mature spores have been seen.

Spores are dispersed by wind, possibly over very long distances.

Comparison

The two ferns of Svalbard (Botrychium excepted) are easily distinguished. Woodsia glabella has jointed petioles leaving stiff stumps on the caudex, once dissected blades, sori submarginal, and indusium hairy and firm; Cystopteris fragilis has petioles not jointed, blades twice dissected, sori well inside the margin of pinnulae, and indusium glabrous and deciduous.

The northern fern species most similar to Woodsia glabella is Asplenium viride (common on the mainland but not found in Svalbard). It differs in having no joint on the petiole, entire (but dentate) pinnae, and linear sori along the main veins.

Habitat

In crevices in calcareous cliffs and boulders, in very dry heath on firm, stone-rich calcareous substrate. The species is an obligate calciphile.

Distribution

Thermophilous. Very rare in Svalbard and confined to two fjords on W Spitsbergen: At Kapp Wærn between Ekmanfjorden and Dicksonfjorden on the north side of Isfjorden (and also an old find from 'Nordfjorden' which may be the same locality), and at several sites at Ossian Sars-fjellet and Blomstrandøya in the inner parts of Kongsfjorden. All localities are in the middle arctic tundra zone and the weakly continental sector.

Woodsia glabella is arctic circumpolar and one of the two ferns with very wide ranges in the Arctic (the other being Cystopteris fragilis). It also reaches south into mountains in the boreal zone, in Europe to N Norway.

Comments

The extreme rarity of this species in Svalbard suggests that its local reproduction is very poor or near absent. The presence of several stands at Ossian Sars-fjellet could vouch for some reproduction but the observed occurrences on Blomstrandøya and Kapp Wærn, with several 'individuals', could both be due to fragmentation of rhizome through a long period of time, perhaps millennia. Fern spores are very easily dispersed by wind over long distances. The scarcity in Svalbard may be due to local climatic conditions rather than to dispersal barriers. All observed Svalbard plants are stunted, much more so than plants found in, e.g., Greenland and arctic Russia.

Literature

No cited literature