Kōrero: Ferns and lycophytes

Whārangi 4. Habitat

Ngā whakaahua me ngā rauemi katoa o tēnei kōrero

Ferns and lycophytes are found in most land and freshwater environments in New Zealand, with the exception of the highest mountain tops.

Coast and cliff

Few ferns thrive on exposed coast or dry, inland rock faces, but those that do are equipped for survival. Coastal ferns such as Blechnum blechnoides, B. durum, shore spleenwort (Asplenium obtusatum) and Asplenium appendiculatum have fleshy or leathery fronds that withstand salt spray and protect against desiccation. Ferns growing on dry rock faces are usually covered in hairs or scales that protect against drying winds and intense sunlight.

Forest

Most of New Zealand’s ferns and lycophytes are found in the forest. Many species are confined to moist, shady, lowland forest. This is the natural environment of filmy ferns, hen and chickens fern (Asplenium bulbiferum), gully fern (Pneumatopteris pennigera) and kiwakiwa (Blechnum fluviatile).

The dampness of the soil has a bearing on which species grow. Silver tree fern (Cyathea dealbata) and crown fern (Blechnum discolor) can tolerate drier conditions and are more likely to be found on upper slopes and ridges than in damp gullies.

At higher altitudes, in wet mountain forests, large clumps of crepe ferns (Leptopteris hymenophylloides and L. superba) are a striking feature. Their thin, translucent fronds are similar to a filmy fern, but standing up to a metre tall, crepe ferns are unlikely to be mistaken for the much smaller filmy fern species.

Forest epiphytes

Epiphytes and climbing ferns are common in wet forests. Four species of fork fern (Tmesipteris) grow on the fibrous trunk of tree ferns. Strange-looking, they lack roots, and consist of a protruding stem with flattened leaves. Hanging clubmoss (Huperzia varia), hanging spleenwort (Asplenium flaccidum) and sickle spleenwort (A. polyodon) are associated with large perching lilies (Astelia and Collospermum), and are often found hanging out of clumps of these nest epiphytes.

Disturbed ground

Some ferns prefer disturbed ground. Ring fern (Paesia scaberula), water fern (Histiopteris incisa) and thousand-leaved fern (Hypolepis millefolium) quickly colonise exposed ground when canopy trees are overturned in strong winds. They die out when shaded by other species. According to fossil pollen records, bracken fern (Pteridium esculentum) increased dramatically following the arrival of humans in New Zealand. It grew quickly in areas of burnt forest, and repeated fires led to its persistence at a site, for it could re-sprout from underground stems – an ability few other New Zealand plants have.

Alpine areas

About 20 species of fern and lycophyte grow in alpine areas. Alpine shield fern (Polystichum cystostegia) grows in the shelter of large boulders or tussock grasses in summer. The fronds die back to a central tuft during winter. Two alpine clubmosses, Huperzia australiana and Lycopodium fastigiatum, are found in a variety of subalpine and alpine environments from bogs to rock fields. At very exposed sites, L. fastigiatum is usually bright orange.

Warm environments

A few tropical species, including the soft fern (Christella dentata) and swamp fern (Cyclosorus interruptus) survive in the far north, where they are safe from frosts. Also frost-free, the thermal areas of the central North Island such as Karapiti, Waimangu and Ōrākei Kōrako are home to the fork fern (Psilotum nudum) and ladder fern (Nephrolepis flexuosa), which grow on heated ground along banks or tracks.

Lakes

The pillwort (Pilularia novae-zealandiae) and quillwort (Isoetes species) grow submerged in lakes and alpine tarns. Pacific azolla (Azolla filiculoides) forms floating mats on the surface of ponds, often appearing bright reddish-purple in summer.

Me pēnei te tohu i te whārangi:

Patrick Brownsey, 'Ferns and lycophytes - Habitat', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/ferns-and-lycophytes/page-4 (accessed 7 December 2019)

He kōrero nā Patrick Brownsey, i tāngia i te 24 Sep 2007