Friday, October 19, 2007

Resurrection fern


Like the rest of the Eastern U.S. this week, southeast Missouri finally received rain and cooler weather. Storms traditionally rumble into the area over the park, sending leaves and branches flying off the drought-stressed trees. I'm never very eager to head into the park after a storm, mainly because I don't like seeing carnage: huge trees fall across the trail, enormous branches block the roads and shellbark hickory nuts make running the trails impossible. Usually the day after a storm, I have a date with a chainsaw.

Before I moved here, the National Champion Swamp Chestnut oak, the largest of its kind in America, lost roughly 40% of its crown during a storm. The large branches remain right next to the tree where they landed, ever slowly decomposing. Of course, the tree is likely no longer the National Champion (up for the title again in 2008) thanks to the missing branches. When the branches fell in what was surely a deafening crash, they brought to the ground level a thriving population of resurrection ferns.

Found only east of the Rockies, resurrection fern grows on the high branches of oaks and cypresses in humid regions. One of only two ferns recorded from the park, resurrection fern is particularly notable because it traditionally grows in old growth forests where Spanish moss grows. We don't have Spanish moss here, but we do have stately oaks and cypresses.

Resurrection fern is an epiphyte, which means it gathers its nutrients from the air, rainwater, and particles that happen to land on the bark upon which it grows. Epiphytes are unlike parasites in that they do not receive nutrients from their host plant. While most ferns dry up and reproduce by spores during times of drought, resurrection ferns can lose up to 76% of its water content and remain alive. Most other plants can only lose up to 12% of their moisture before they die.

During dry spells, resurrection ferns curl their fronds inward, allowing the underside to be exposed to air and available moisture. When it rains, the fronds unfurl and remain green for at least a couple of weeks. I've kept resurrection fern alive in a tank with dart frogs for about three weeks under constant hydration. The small fronds on a bit of live oak bark shriveled up after a month, despite having moisture. It probably realized that it was being held captive.

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