It may be a small correction, but it is far from negligible as far as forest ecologists and carbon cycle specialists are concerned. The error lay in a formula established almost 50 years ago (in 1971) for calculating basic wood density. Given that basic density is used to assess the amount of carbon stored in a tree, the fact that the formula had to be corrected meant that forest carbon stocks may have been overestimated by 4 to 5%. “This new formula should enable us to determine more accurately the role of forests in the carbon cycle and the impact of deforestation on climate change” , says Ghislain Vieilledent, an ecologist with CIRAD who was the corresponding author of the work published in the journal American Journal of Botany on 16 October.
For more than 70 years, CIRAD has had a database on 1300 wood species and almost 4500 trees. It was when they came to promote this resource that Ghislain Vieilledent and his colleagues at CIRAD and at Paul Sabatier University in Toulouse discovered an incoherence in a conversion factor: the one used to compute the basic density of a tree based on wood density at 12% moisture, which corresponds to the average wood moisture content in temperate regions. Since this technical characteristic is widely available in wood technology databases, ecologists only have to apply a conversion factor to it in order to establish the basic density of a tree species. However, it was precisely that conversion factor that did not tally with the researchers’ new calculations.