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Sycamore Trees

Cristy Meiners

This morning, our lawn looked like the aftermath of some sort of tree party. But instead of scattered confetti, big pieces of bark were strewn all over, deposited by the giant sycamore tree that grows in our neighbor's backyard.

These trees thrive in city settings because of their rapid growth and tolerance of pollution.

Sycamores are easy to spot thanks to their distinctive thin bark that looks like army camouflage. As the irregular blotches of tan and green pieces of bark flake off, or exfoliate, they reveal a creamy inner trunk, smooth to the touch.

On the surface, this pattern seems simple to explain: As the sycamore trunk gets bigger in diameter, the older bark has to push outward, cracking off its rigid plates.

But of the over 70,000 species of trees on our planet, only a handful of them shed their bark. Why? Botanists don’t have a definitive answer yet, but I’ll share some current theories.

For starters, bark is a dead layer of tissue that protects trees from losing moisture, from fire and from animal attacks. Since thin-barked trees lack the protection that thick bark provides, one theory is that shucking off old bark helps jettison insects and disease-causing microbes, like snakes when they shed their skins. And sycamores’ pale trunks make caterpillars more visible for birds to find and pick off, an additional mode of protection.

Most photosynthesis — how trees capture energy — takes place in green leaves. But another theory claims that think-bark trees like sycamores may capture energy through their trunk surfaces. It’s not an entirely out there idea — the process is often found in desert plants, where rates of stem photosynthesis can reach up to 60% of the leaf photosynthetic rate.

But this research is in its infancy, so stay tuned for updates!

And although hosting a sycamore may not be your best choice if you want a perfectly manicured lawn, these trees are great for providing compelling questions about nature, which I think makes that messy, post-party look of your lawn entirely worth it.

Dr. Nalini Nadkarni is an emeritus professor of both The Evergreen State College and the University of Utah, one of the world’s leading ecologists and a popular science communicator. Dr. Nadkarni’s research and public engagement work is supported by the National Geographic Society and the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. @nalininadkarni
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