Data from: Marcescence and prostrate growth in tree ferns are adaptations to cold tolerance

Cold tolerance strategies in plants vary from structural to biochemical.
Many temperate tree fern taxa are marcescent—retaining whorls of dead
fronds encircling the upper trunk—or develop short or prostrate trunks
possibly to insulate against cold temperatures that might detrimentally
affect their trunks and growing crowns. We asked the following questions:
(1) do global growth patterns traits of temperate taxa relate to
environmental factors associated with latitude (a proxy for seasonality
and frost tolerance) and elevation (a proxy for temperature), (2) do
growth patterns of tree ferns in New Zealand vary along a temperature
related gradient, and (3) do marcescent tree fern skirts insulate the
growing crown from sub-zero temperatures? We review the global and
regional distributions of these structural and morphological traits within
Cyatheales. Further, we assess the patterns of tree fern marcescence, and
other traits potentially associated with cold tolerance (no trunk,
prostrate, short-trunked), by comparing the ecological niches of nine taxa
of the Cyatheales along environmental gradients across New Zealand.
Finally, we conducted a field experiment to assess the thermal insulation
properties of tree fern marcescent skirts. We identified significant
trends among growth forms, marcescence, and envionmental gradients
consistent with our hypothesis that these are adaptations to tolerate
cold. In addition, our field experiments provide quantitative evidence
that marcescent skirts have a strong insulating effect on tree fern
trunks. The Cyatheales have evolved several strategies to protect the pith
cores of their trunks from extreme cold temperatures in temperate forests
allowing them to capture niche space in environments beyond the tropics.