Scientists say they have pieced together the world's oldest known tree from two fossils dating back 385 million years, a discovery they say could help explain the role early forests played in climate change.

The researchers from the U.S. and Britain said the fossilized trunks and branches found two years ago near Gilboa, N.Y., match those of stumps first discovered in the region over 100 years ago.

The findings, published in the April 19 issue of the British scientific journal Nature, shed new light on the appearance and function of these early trees.

The trees, of the genus Wattieza, stood at least eight metres high and resembled palm trees, with fern-like branches instead of the flat, round leaves found in many trees today.

Wattieza is at least 15 million years older than Archaeopteris, which had been identified in 1999 as the earliest known tree.

The stumps discovered in 1870 in Gilboa had confounded attempts to match them for over 100 years, making the discovery of their other halves a significant find, Cardiff University Prof. Christopher Berry, one the co-authors of the study, said in a statement.

He also said the make-up of these early forests shed new light on the role they might have played in the evolution of early animals.

'Spectacular find'

"This is a spectacular find, which has allowed us to recreate these early forest ecosystems," he said.

"Branches from the trees would have fallen to the floor and decayed, providing a new food chain for the bugs living below."

The rise of forests in the late middle Devonian period might also have been responsible for a cooling of the planet, paving the way for more complex organisms, said Berry.

"This was also a significant moment in the history of the planet. The rise of the forests removed a lot of carbon dioxide from the atmosphere. This caused temperatures to drop and the planet became very similar to its present-day condition," he said.

Berry contributed to the paper along with Linda VanAller Hernick and Frank Mannolini from the New York State Museum and William Stein, a paleobiologist at Binghamton University in Binghamton, N.Y.