To improve estimates of neotropical forest carbon stocks more direct measurements are needed: An example from the Southwestern Amazon

• Published in: Forest ecology and management 2024-10, Vol.570, p.122195, Article 122195
• Main Authors: Melo, Antonio Willian Flores de, Lima, Adriano José Nogueira, d’Oliveira, Marcus Vinicio Neves, dos Santos, Joaquim, Brown, I. Foster, do Amaral, Eufran Ferreira, Silva, Sonaira Souza da, Oliveira, Igor, de Camargo, Plínio Barbosa, Higuchi, Niro
• Format: Article
• Language: English
• Subjects: Carbon stock uncertainty; Open forests; Plant allometry; Southwestern Amazon; Tree biomass
• ISSN: 0378-1127
• DOI: 10.1016/j.foreco.2024.122195

Tropical forests play a critical role in the global carbon cycle, storing 40–55 % of terrestrial plant carbon and significantly contributing to primary productivity. However, uncertainties persist in estimating carbon stocks and fluxes, exhibiting variation across the Neotropics, Africa, and Asia tropical forest regions. Despite hosting some of the most densely sampled forests, significant uncertainties persist in biomass and forest carbon stock estimates in the Neotropics. Although the Southwestern Amazon (SWA) forests span over 20 million hectares, no specific biomass or above- and below-ground carbon model has been calibrated for this region thus far. In our study, we conducted direct forest inventories in the SWA to address the following question: Do the allometric patterns, biomass, and carbon stocks observed in the Southwestern Amazon differ from those found in other regions of the Amazon or Pantropical? Our research reveals substantial differences in water and carbon content, biomass stocks, above- and below-ground oven-dry biomass ratios, and allometric patterns between SWA forests and other Amazonian and Pantropical forests. We have demonstrated that these differences result in overestimations of forest biomass when applying allometric equations developed for other Amazonian and Pantropical regions to the open forests of Southwestern Amazonia. This overestimation can reach up to 37 % when using equations from the eastern Amazon, and between 26 % and 46 % depending on the applied Pantropical equation. The use of an inappropriate factor for the root-to-shoot ratio in the Southwestern Amazon (SWA) can lead to overestimates of belowground oven-dry biomass by up to 20 %. To reduce uncertainties related to estimates of forest carbon stock and flux in Neotropical forests, it is necessary to enhance the density of direct biomass measurements, particularly in southwestern Amazonia. •Improvement of tropical forest carbon stock estimates depends on increasing the direct biomass measurements.•We developed the first set of allometric equations for Southwestern Amazon (SWA) Forests.•The allometric patterns of the forests of the SWA are distinct from the Pantropical regions.•Equations derived from other regions may overestimate SWA forest biomass by up to 46 %.•Our results fill a significant gap in biomass estimation for SWA Forests.