Sky-high PNG trees cause re-think on forest assumptions

Sky-high PNG trees cause re-think on forest assumptions

Remote mountains in Papua New Guinea could be home to some of the world’s tallest trees at extreme altitudes, scientists said Wednesday, with a new study questioning assumptions about forests at such heights.

Trees located far above sea level do not usually grow more than 15 metres (49 feet), but scientists from Australia and Canada found those in the Pacific nation’s pristine highlands were up to 40 metres tall.

“Unexpectedly, forest biomass had a major peak at altitudes of 2,400-3,100 metres, an altitude where forests fail to grow more than 15 metres tall in other parts of the world,” said Michael Bird of James Cook University.

The discovery questioned the belief that “mountains make small trees” with forests at such altitudes often “squat and gnarly”, lead author, Michelle Venter of Canada’s University of Northern British Columbia, said.

“However, we recorded more than 15 tree families with individuals growing 30-40 metres tall at extreme altitudes, which brings this assumption into question.”

The scientists studied 195 forest plots in largely unresearched Morobe Province — from coastal lowlands at 50 metres above sea level to tropical forests at 3,100 metres — with their findings published in the Global Change Biology journal.

University of Queensland’s John Dwyer said the study could push researchers to re-evaluate the ideal environments for growing very large trees.

“We got excited when we realised that the unique climate conditions found on the mountain tops of PNG were remarkably similar to those of temperate coastal areas known to grow the largest trees in the world,” he said.

Such climates were not unlike those in the mid-west coast of the United States, home to large coastal redwoods, Dwyer added.

Giant sequoias, which are closely related to redwoods and found in California, are the world’s largest trees and on average grow to more 250 feet (76.2 metres), according to the US’ National Park Service.