Plants, long known to be the "lungs" of the Earth that create oxygen, may also play a role in electrifying the atmosphere, Australian researchers say.

A link between trees and electricity has long been theorized but researchers from Queensland University of Technology in Brisbane say they think they may have finally discovered it.

In experiments conducted in six locations around Brisbane, the researchers found the positive and negative ion concentrations in the air were twice as high in heavily wooded areas than in open grassy areas, such as parks.

Natural ions in the air are mainly created by ionization due to two processes, radiation from the gas radon in air and cosmic radiation from space.

Radon is a byproduct of the radioactive decay of radium, which is present in minute quantities in rocks and is continually exhaled by the ground.

"Because radium is found in rocks and radon is soluble in water, ground water is particularly rich in radon," researcher Rohan Jayaratne said.

"Trees act as radon pumps, bringing the gas to the surface and releasing it to the atmosphere through transpiration -- a process where water absorbed by the root system is evaporated into the atmosphere from leaves," he said in a university release Wednesday.

"This is especially prevalent for trees with deep root systems, such as eucalyptus."

In a eucalyptus forest, trees may account for up to 37 percent of the radon in the air, he said.

The findings, he said, have potentially important implications for the atmosphere, climate and human health.

"Although there is an established link between airborne particles and human health, the role of ions is largely unknown," he said.

"We do not believe that ions are dangerous -- the danger comes from the pollutants. If there are no dangerous particles in the air to attach to the ions there is no risk of ill health."