The Most Southern Tree Fern

Explanation: Here is a resident of the moist montane environments of New Zealand: the southernmost tree fern. This is Smith's, or soft, tree fern.

Tree ferns are a primitive and ancient division of terrestrial ferns. Basically, any fern that forms a main bole (stem) that raises its fronds (leaves) above ground level can be called a tree fern. But what makes this one special is its growth form and its location.

In New Zealand, Smith's tree fern is the only tree fern that produces and maintains a "skirt" of dead fronds that hang around and cover the stem as the plant grows.

In an earlier EPOW episode, we explored the ecology of tree "skirts."
Species of birds, reptiles, and other organisms can use the dense
skirts of trees, palms, and other plants, as hiding and nesting habitat.

Apparently, such use of the skirts of Smith's tree ferns is yet to be studied.

Who know what surprises may lie beneath and within those dead fronds?

The trunks of tree ferns are unlike those of conifer and hardwood trees. Tree fern trunks are essentially vertically-growing rhizomes, stems that usually grow along and under the ground, but in tree ferns they grow upward, carrying a canopy of fronds.

Cross-section of the vertical stem of a Smith's tree fern,
showing a central pith surrounded by highly crumpled tissue,
the structure of which likely providing structural support.

Because of their sturdy structure, the trunks have been used
as building material and fencing.

Welcome to Jurassic Park ... or at least to a
botanical lineage common during
the Jurassic Period (200 to 145
million years ago).

This hold-over -- Smith's tree fern -- is indeed
the most southern-growing tree fern
in the world, found in New Zealand
as far south as Stewart Island.

Information:
Brock, J.M.R., G.L.W. Perry, W.G. Lee, and B. Burns. 2016. Tree fern ecology in New Zealand: a model for southern temperate rainforests. Forest Ecology and Management 375:112-126.

EPOW - Ecology Picture of the Week