Trees accelerate growth as they get older and bigger, study finds

Findings contradict assumption that old trees are less productive and could have important implications for carbon absorptionMost living things reach a certain age and then stop growing, but trees accelerate their growth as they get older and bigger, a global study has found.The findings, reported by an international team of 38 researchers in the journal Nature, overturn the assumption that old trees are less productive. It could have important implications for the way that forests are managed to absorb carbon from the atmosphere."This finding contradicts the usual assumption that tree growth eventually declines as trees get older and bigger," said Nate Stephenson, the study's lead author and a forest ecologist with the US Geological Survey (USGS). "It also means that big, old trees are better at absorbing carbon from the atmosphere than has been commonly assumed."The scientists from 16 countries studied measurements of 673,046 trees of more than 400 species growing on six continents, and found that large, old trees actively fix large amounts of carbon compared to smaller trees. A single big tree can add the same amount of carbon to the forest in a year as is contained in an entire mid-sized tree, they found."In human terms, it is as if our growth just keeps accelerating after adolescence, instead of slowing down. By that measure, humans could weigh half a tonne by middle age, and well over a tonne at retirement," said Stephenson."In absolute terms, trees 100cm in trunk diame...

Source: Guardian Unlimited Science - January 15, 2014 Category: Science Authors: John Vidal Tags: theguardian.com World news Trees and forests Climate change Environment Carbon emissions Science Source Type: news