Table 1.
Terms used to report tropical forest wood density (g cm−3) in this paper, together with their definitions and data requirements. Identity-rich metrics use species identity to derive the wood density of each and every tree. Identity-poor metrics simply apply aggregate mean values to all trees, plots, forest types, or landscapes. We include these latter approaches which implicitly assume that species identity does not matter to assess the impact of using incomplete biological identities on forest biomass estimates. Note that whether identity-poor or identity-rich, the community-mean, plot-mean, forest-type-mean, landscape-mean, Amazon-mean wood density metrics can all be either abundance-weighted or basal-area-weighted. We recommend use of identity-rich basal-area-weighted wood density whenever possible (highlighted here and Table 2)
| Term | Definition | Data required to estimate |
|---|---|---|
| Identity-rich metrics | ||
| Species wood density | Species ‘basic specific gravity’, the oven-dry mass of a wood sample divided by its green volume (cf. Chave et al. 2006) | Ideally based on multiple individuals and accounting for radial variation from core to pith. Either from compilations (Zanne et al. 2009) or local measurements (e.g., Goodman et al. 2014a, b) |
| If no species wood density measurements available, allocate the genus-level mean, else the family-level mean (Baker et al. 2004) | ||
| Community-mean wood density | Community-mean wood density (WD), based on each tree’s species wood density weighted by the abundance of each species | Additionally requires species-abundance data for the plot |
| Community-mean wood density: basal-area-weighted | Community-mean WD, based on each tree’s species WD and weighted by the basal area of each species (e.g., Lewis et al. 2013) | Additionally requires accurate, above-buttress diameter measurement of every individual tree |
| Identity-poor metrics | ||
| Plot-mean wood density | The mean WD of all trees in the plot, based on species WD with species’ contributions weighted by their abundance or basal area | |
| Forest-type-mean wood density | The mean value of ‘plot-mean wood density’ averaged across contributing plots in the forest type | In the case of the Tambopata landscape, computed separately for Altura and Bajio forest typesa |
| Landscape (Tambopata-wide) mean wood density | The mean value of ‘forest-type-mean wood density’, averaged across contributing forest types in the landscape | In the case of the Tambopata landscape, the mean of the mean values for Altura and Bajio forestsa |
| Amazon-mean wood density | The mean value of ‘plot-mean wood density’, averaged across contributing plots in Amazonia | Published wood density values from plots across Amazonia (Mitchard et al. 2014) |
aAltura and Bajio forest types represent the two major units within the Tambopata landscape. The folk nomenclature used here corresponds to geomorphical units (erosional, depositional) and chronological units (Pleistocene, Holocene). See text for details