AbstractA large portion of the terrestrial vegetation carbon stock is stored in the above-ground biomass (AGB) of tropical forests, but the exact amount remains uncertain, partly due to the difficulty of making direct, whole-tree measurements. We harvested four large tropical rainforest trees (stem diameter: 0.6–1.2 m, height: 30–46 m, AGB: 3960–18 584 kg) in a natural closed forest stand in East Amazonia, and measured above-ground green mass, moisture content and woody tissue density. We found approximately 40 % of green mass was water, and the majority of AGB was most often found in the crown, but varied from 42–62 %. Woody tissue density varied substantially intra-tree, with both height and radius, but variations were not systematic inter-tree. Terrestrial lidar data were collected pre-harvest, from which volume-derived AGB estimates were retrieved. These estimates were more accurate than traditional allometric counterparts (mean tree-scale relative error: 3 % vs. 15 %). Error in lidar-derived estimates remained constant across tree size, whilst error in allometric-derived estimates increased up to 4 −fold over the diameter range. Further, unlike allometric estimates, the error in lidar estimates decreased when up-scaling to the cumulative AGB of the four trees. Terrestrial lidar methods therefore can help reduce uncertainty in tree- and stand-scale AGB estimates, which would substantially advance our understanding of the role of tropical forests in the global carbon cycle.
New insights into large tropical tree mass and structure from direct harvest and terrestrial lidar
