New formula and conversion factor to compute basic wood density of tree species using a global wood technology database

Basic wood density is an important ecological trait for woody plants. It is used to characterize species performance and fitness in community ecology, and to compute tree and forest biomass in carbon cycle studies. While wood density has been historically measured at 12% moisture for construction purpose, it is convenient to convert this measure to basic wood density, i.e. the ratio of dry mass over green volume. Basic wood density can then be used to compute tree dry biomass from living tree volume. Here, we show that previous conversion factors used to convert densities at 12% moisture into basic wood densities are inconsistent. We derive a new, exact formula to compute the basic wood density Db from the density at moisture content w denoted Dw, the fibre saturation point S, and the volumetric shrinkage coefficient R. We estimated a new conversion factor using a global wood technology database where values to use this formula are available for 4022 trees collected in 63 countries (mostly tropical) and representing 872 species. Based on theory and data, we found that basic wood density could be inferred from the density at 12% moisture using the following formula: Db = 0.828 D12. This value of 0.828 provides basic wood density estimates 4-5% smaller than values inferred from previous methods. This new conversion factor should be used to derive basic wood densities in global wood density databases. This would prevent overestimating global forest carbon stocks and allow predicting better tree species community dynamics from wood density.

VIEILLEDENT Ghislain;  FISCHER Fabian Jörg;  CHAVE Jerome;  GUIBAL Daniel;  LANGBOUR Patrick;  GÉRARD Jean; 

2018-10-17

BOTANICAL SOC AMER INC

JRC112083

0002-9122,   

https://www.biorxiv.org/content/early/2018/07/01/274068,    https://publications.jrc.ec.europa.eu/repository/handle/JRC112083,   

10.1101/274068,