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Lightning & Trees

S. Linzbacher
WikiMedia Commons

Envision a bolt from the sky striking a single tall tree in an open field.

That electric charge travels through the layer of moist sap just beneath the bark, heating and expanding as it goes, then blasting off the bark, and killing the tree.

That’s what lightning can do to just one tree. But what about a whole forest?

Over the past two decades, a team of researchers has monitored the number of lightning strikes at their research site in Panama. They estimated that tropical forests around the globe experience over 60 million strikes each year, which can kill up to 40% of the largest trees in those forests.

Obviously, the tallest trees are the most directly vulnerable. But these researchers discovered another mortality factor — the presence of woody vines or “lianas.” These plants germinate in the forest floor soil and then grow into the tree canopy, using understory stems for support. Researchers found that the greater the density of lianas, the larger the number of small trees lightning damaged or killed.

With their long stems filled with water, lianas act as super conductors for electricity. They physically connect canopy trees to the forest understory, like jumper cables between cars, delivering deadly electrical current from tall trees to the small trees that would otherwise be unaffected by a lightning strike. The death of those smaller trees and saplings can ultimately change the future composition of the whole forest.

As their research deepens, these scientists better understand the complex interconnections among trees, knowledge that comes not as a bolt of lightning, but through careful observations over time.

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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