Effects of wood density and the height-x-diameter relationship on biomass differences between three widespread Amazonian forest types
Bruce
Walker
Nelson, INPA-Ecologia, bnelson@internext.com.br
(Presenting)
Mabiane
Batista
França, INPA- Curso de PG em Ciências Florestas Tropicais, Mabiane.Batista-Franca@Uhb.Fr
Euler
Melo
Nogueira, INPA- Curso de PG em Ciências Florestas Tropicais, eulerquait@inpa.gov.br
Átila
Cristina
Oliveira, INPA - Curso de PG em Ecologia, atilaoli@inpa.gov.br
Spatial models of the distribution of carbon stocks across Amazonia rely ultimately on allometric regressions relating tree biometric variables to tree or stand biomass. Regressions for individual trees developed in Amazonian primary forest, using diameter at breast height or above buttress (DBH), have been derived only for dense forests on infertile soil. Carbon emissions will be overestimated if such models are applied to open forests or to dense forests on more fertile soils, both of which are common in the Amazonian Arc of Deforestation. In a central Amazon dense forest, where commonly used allometric models were developed, trees are taller at any given DBH than in two southwest Amazon forests. Wood density with bark at breast height is 0.712 +/- 0.119 (average +/- 1 std dev; n=310), greater than both SW Amazon open (0.512 +/- 0.176; n=92) and SW Amazon dense (0.600+/- 0.160; n=97) forest types. Effects on biomass, of lower wood density and shorter stem height, were devised in small calibration inventories then applied to larger inventories where only DBH is available. The wood density correction alone reduces estimated above-ground stand biomass (trees over 5 cm DBH) by 28% in the SW Amazon open forest and by 16% in the SW Amazon dense forest. When tree height effects are also considered, accumulative reduction of estimated biomass in these two forest types is 40% and 22%, respectively.