Record Large Trees Found at Extreme Altitudes

The first field campaign surveying Papua New Guinea's lush primary forests from the coast to clouds has revealed high mountain tops may house the largest trees recorded globally at such extreme altitudes.

They studied 195 forest plots in the rugged and remote Morobe Province along an elevation gradient spanning from the coastal lowland forests (50 meters) to upper montane tropical forests (3100 meters).

Unexpectedly, the researchers found that the forest biomass had a major peak at altitudes of 2,400-3,100 meters, altitudes where forests struggle to reach more than 15 meters in other parts of the world.

"However, we recorded more than 15 tree families with individuals growing 30-40 meters tall at extreme altitudes," Michelle Venter, a postdoctoral fellow at the University of Northern British Columbia, Canada, who led the study.

The study also involved the University of Queensland's John Dwyer and James Cook University's Professor Michael Bird.

"The study may force a rethink of what we know about the ideal environments for growing very large trees," said Dwyer.

Venter led seven field expeditions in areas far from roads and villages, with the help of more than 70 field assistants from five forest-dependent communities, working on slopes of up to 88 degrees.

"Tropical montane forests are typically squat and gnarly," he said. "Current thinking is that tall mountains make small trees, [but our findings] brings this assumption into question."

The tallest trees included a 41-meter high Nothofagus starkenborghii, one of the southern beeches whose ancestors dominated Gondwanan forests for millions of years.

Dwyer said the researchers became excited when they realized the unique climate conditions found on mountain tops of PNG were remarkably similar to those of temperate maritime areas known to grow the largest trees in the world.

"Think of the foggy midwest coast of the USA, which boasts the epically large coast redwoods," Venter said.

The world's tallest known tree is a 115.8-meter coast redwood found in California and the second-tallest reliably measured specimen is a 99.82-meter mountain ash from the Arve Valley in Tasmania.