CO2 fixation estimation for trees

[meyer]

Is anyone aware of a formula for estimating (however crudely) an
individual treeÕs CO2 fixation? I would like to use it for an
elementary school science assignment. The idea would be something the
kids could use to estimate the CO2 fixed and O2 generated by trees in
their yards, and compare it to the CO2 produced by their parentÕs cars.
Ideally, something based on the diameter, height and
deciduous-evergreen-conifer status would be great, but even
small-medium-large tree estimates would help. Thanks.
Larry Meyer
Meyer at msscc.med.utah.edu