Cold but not rigid: researchers discover a surprising plant phenomenon


Muskoxen near Toolik Field Station in Arctic Alaska graze on exposed shrub branches above the snow surface on a hot day in April 2020. (Photo by Seth Beaudreault/Station of Toolik field)

Juneau, Alaska (KINY) – Peter Ray and Syndonia Bret-Harte have studied Arctic plants for 50 years, but recently discovered there was even more to learn when an accidental experiment led to a startling discovery about the how these plants behave in the snow.

Their discovery warns of a potential new mechanism for future Arctic warming.

Ray, a professor emeritus at Stanford University, and Bret-Harte, a professor at the Fairbanks Institute of Arctic Biology at the University of Alaska, found that arctic and boreal woody shrubs and trees become more “bendable” when frozen. The researchers named the counterintuitive phenomenon “cryocampsis,” from the Greek roots “cryo” for “frozen” and “campsis” for “bending.”

Scientists reported on the cryocampus in a study published in the Proceedings of the National Academy of Sciences Nexus.

“I’ve never had such a serendipitous project before this one,” Bret-Harte said.

One day in 2006, Ray and Bret-Harte were testing the ability of shrub branches to bend under the weight of winter snow to understand how these plants affect the reflectivity, or albedo, of the Arctic.

The decreasing albedo of this region is a key factor in Arctic amplification — the fact that the Arctic is warming four times faster than the rest of the world.

“We were doing spring experiments on deck outside a lab at Toolik Field Station,” Bret-Harte said, “and we had a cold night that dropped below freezing. Peter came back the next day morning and said, ‘Hey, that’s weird. What’s going on here?'”

Common sense would say that freezing temperatures made the branches stiffer. But to Bret-Harte’s surprise, the branches bent even more in the cold.

Cryocampsis helps maintain the high albedo of the snowpack, Bret-Harte said.

“When the darker shrubs are buried under the more reflective snow surface, most of the solar radiation is reflected back into space, preventing the climate from warming up as quickly,” she said.

Although this is not something that currently affects the trajectory of the climate, it could change as future warming could cause the shrubs to not bend as much and stand above the snow instead, he said. she adds.

“Right now it’s like holding back the warming,” she said. “If you warm things up enough for that brake to be released, it could speed up the warming.”

The researchers confirmed this previously undescribed phenomenon through 15 years of experimentation with financial support from the National Science Foundation. They collected branches from nearly 200 species of plants around the world and tracked their bending at varying temperatures using a custom cantilever device that Ray built. All arctic plants and most boreal plants exhibited a cryocampus. Very few temperate and Mediterranean species and no tropical species have done so.

Syndonia researchers Bret-Harte and Peter Ray designed and built the apparatus pictured above in 2006 to simulate bending of branches under heavy snowpack at UAF’s Toolik field station. A branch is held in place at one end and a weight is placed at the free end. A needle attached to the free end follows the movement of the branch as it bends under the weight and rises once the weight is unloaded. (Photo by Peter Ray.)

According to Bret-Harte, the cryocampus likely evolved from the protective benefits it bestows during freezing northern winters.

“If you are below the snow surface in winter, you are not exposed to abrasive snow crystals blowing in the wind above the snow surface. You’re not exposed to herbivores,” Bret-Harte said.

Ray and Bret-Harte attribute the cryocampus to the movement of water between plant cell walls and the ice that forms in the woody internal piping system of branches. They suspect that there is something different about Norse species, like a protein or carbohydrate, that sets them apart from non-Nordic species. The couple is collaborating with a Danish chemist to find out.

“The crazy thing is when you heat up a branch with a load on it, it actually lifts the loads,” Bret-Harte said. “Where this energy comes from is a bit of a mystery.”

“There’s a lot to dig here,” Bret-Harte said. “It’s not the end of the story, it’s the beginning.”


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