Unlocking the Forests' Secret Store--Carbon Dynamics in Australia
9/2/99
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Title: Unlocking the forests' secret store
Source: Sydney Morning Herald
Status: Copyright 1999, contact source for permission to reprint
Date: September 2, 1999
Byline: JAMES WOODFORD, Science Writer
Phillip May is a logging contractor and after years of loading and
unloading his truck he can tell almost to the kilogram how much a
trunk weighs even before a tree has been felled.
But this week, instead of felling for timber, Mr May has been helping
a team of scientists to weigh entire trees - roots, crowns, bark and
trunks - to help them work out how much carbon is locked up in a
typical forest.
In an average tree the main trunk - the part of greatest interest to
foresters - makes up 40 per cent of its bulk, the roots between 20
and 40 per cent and the crown the rest. About half of the mass of a
freshly felled tree is made up of water absorbed from the ground by
its roots, and at least a quarter is carbon that the tree has
converted from atmospheric carbon dioxide.
According to State Forests' carbon dynamics research officer, Dr
Annette Cowie, one tonne of carbon in a tree is equivalent to 3.7
tonnes of carbon dioxide in the atmosphere. Trees make this using an
enzyme called rubisco, which turns carbon dioxide into a complex
sugar which eventually becomes wood. Over the last few months State
Forests has numbered every tree greater than 10 centimetres in
diameter - living and dead - within a two hectare plot in a remote
section of Ourimbah State Forest, on the NSW Central Coast.
There scientists are employing three different techniques in an
attempt to work out the exact "biomass" of trees. One technique
involves remote sensing equipment such as infra-red aerial
photography, a second studying the branches on trees and
extrapolating the results to the entire organism and, the third,
completely uprooting 10 of the 1,300 trees in the study area and
weighing them using a chain harness and electronic sensor that can
measure up to 2.5 tonnes in a single lift. A 31- metre blackbutt gum
yesterday weighed in roots and all at 2.4 tonnes. The team, supported
by the Co-operative Research Centre for Greenhouse Accounting, also
includes scientists from the University of NSW, the Australian
National University and the Queensland University of Technology.
State Forests tree physiologist, Dr Kelvin Montagu, said the study
was important for finding how much carbon is stored in Australia's
forests. From the 10 felled trees that have been "destructively
sampled" the scientists hope to collect enough data to prepare
species specific equations that will allow foresters to estimate
total carbon in their forests by measuring a proportion of the
individual trees.
The data will also be useful as State Forests increasingly moves into
the marketing of its forests as greenhouse sinks, paid for by
polluting industries. "We are estimating that carbon will be worth at
least $US15 ($23) per tonne," Dr Cowie said.
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