This tropical tree species has evolved to benefit from lightning strikes
Lightning strikes may kill untold numbers of trees every year, but one tropical species has evolved to benefit from the sudden jolts of electricity.
The tonka bean tree, aka Dipteryx oleifera, has exhibited the ability to transfer the electricity from lightning strikes onto the parasitic vines that attach to it, according to a paper published last month in New Phytologist. Lightning strikes have also been shown to damage neighboring trees with which the tonka bean tree may be competing for resources, leaving the former unscathed, researchers said.
Dipteryx oleifera consistently shows little damage as a result of lightning strikes, according to the paper.
Scientists studied nearly 100 trees struck by lightning in the Barro Colorado Nature Monument, a lowland rainforest in Panama, between 2014 and 2019. More than half of the trees struck directly were killed, but 10 strikes to tonka bean trees only led to "negligible" damage, while killing 78% of the lianas –the long-stemmed, woody vines – that clung to them, according to the paper.
In addition, all of the tonka bean trees that were struck by lightning survived, while 64% of the other tree species that were struck died within two years. In one single strike, 57 trees were killed but the tonka bean tree at the center of the group survived, according to the paper.
The researchers developed a unique high-definition lightning location system using custom sensors to track and accurately record the strikes, which allowed them to analyze their energy patterns.
The results of the lightning location system were compared against about four decades of tree plot records, which further established the tonka bean tree as the most lightning-resistant species in the forest.
Tonka bean trees have high internal conductivity, which allows electrical currents to flow through them without any heat buildup, according to the paper.
Lightning is a major cause of tree mortality, accounting for up to 40% of the deaths of large trees in lowland tropical forests where the tonka bean trees reside, previous research has shown.
In a typical lightning strike in a tropical forest, the lightning attaches directly to a large-canopy tree and the electrical current moves through air gaps, branches or lianas to damage neighboring trees, according to previous research.
Scientists now believe that lightning plays an "underappreciated role" in tree competition and coexistence, according to the paper. A single tonka bean tree greater than 60 cm (23.6 in.) in diameter is estimated to have been struck at least five times by lightning during its lifetime, according to researchers, helping each time to clear out vines and competitors.
Tonka bean trees can grow up to 130 feet tall and live for hundreds of years, with the lighting strikes likely helping to extend the lifespan of the trees by decades or even centuries, the researchers said.
Little is currently known about the positive effects of lightning on trees and the possibility that lightning can influence tree life history and patterns of biodiversity, according to the paper. Understanding how lightning shapes forest ecosystems could shed light on how resilient they in the face of global warming, which could bring stronger storms and lightning in the future, the researchers said.
