Hosted by Sandra Tsing Loh, The Loh Down on Science is a fun way to get your daily dose of science plus a dash of humor in less than two minutes.
Hosted by Sandra Tsing Loh
Airs Weekdays 2:31, 3:31 and 5:49 a.m.

Fir Coats

Why don't evergreen trees get cold? Because they're wearing fir coats! Seriously.

Do trees get. . . cold?

This is Sandra Tsing Loh with the Loh Down on Science

Saying yes they do! No they don't. Well-- Plant ecologist Brent Heiliker of the University of Pennsylvania wondered how fir trees weather extreme cold.

He studied tree samples from Canada's Northwest Territories, in the dead of winter. He measured the amounts of two types, or isotopes, of oxygen--a heavier one and a lighter one.

The relative amounts of the two oxygen atoms vary depending on temperature. This offers a way to indirectly measure the trees' internal thermostat.

The result? Heiliker calculated that even when the air temperatures hit zero, fir trees' needles remain at a balmy seventy degrees!

But how? Their needles aren't capable of generating heat. The answer: Canadian firs clump their needles together, trapping a layer of still air that acts like a blanket to keep them toasty warm.

It's the trees' very own version of a fir coat. Get it? Fir coat. Cruelty free, of course. No animals except our human listeners were harmed in the making of this pun.