Introduction: Pentaclethra macroloba is a hyperdominant tree in the Amazon estuary of great socioeconomic importance for the region because the oil from its seeds is a powerful herbal medicine. Objective: We aimed to characterize the morphological structure, the morphological adaptations in response to the daily flooding of the Amazon estuary and the biogeographic area of P. macroloba. Methods: Detailed description of the external morphology, from germination to the adult tree, was obtained from individuals located in floodplain forest, Northeast Amazonia. The occupation area and the geographical extension of P. macroloba were determined from point of geographical coordinates of botanical samples deposited in the digital collections of Mobot and SpeciesLink. Results: Adult individuals have adapted structures in response to daily flooding, such as: adventitious roots to increase respiratory efficiency and lenticels in the trunk, serving as a connection point for oxygen transport between the root and the aerial part. Dried fruit favours the activation of the explosive dehiscence mechanism, allowing the seed to be expelled long distance. Deltoid shape of the seed allows water fluctuation and more efficient dispersal. Seedling is phanerocotylar hypogeal and with one pair of reserve cotyledons that provide the seedling an extra source of energy to escape the flood. Germination rate was 78 % and the speed was 0.2 seeds.day-1. Circular buffer method revealed the presence of 123 subpopulations of P. macroloba distributed in a radius of 5 699 943 km² across the Neotropical region. Conclusions: Much of the morphological structures of P. macroloba are adaptive and evolutionary responses to the periodically flooded environment of the Amazon estuary, showing that these environments select the trees, best adapted, to inhabit the flood. P. macroloba has a wide geographical area denotes the plasticity of adapting to different environments, which may justify its monodominance in some regions.
Around 30 Mm3 of sawlogs are extracted annually by selective logging of natural production forests in Amazonia, Earth’s most extensive tropical forest. Decisions concerning the management of these production forests will be of major importance for Amazonian forests’ fate. To date, no regional assessment of selective logging sustainability supports decision-making. Based on data from 3500 ha of forest inventory plots, our modelling results show that the average periodic harvests of 20 m3 ha−1 will not recover by the end of a standard 30 year cutting cycle. Timber recovery within a cutting cycle is enhanced by commercial acceptance of more species and with the adoption of longer cutting cycles and lower logging intensities. Recovery rates are faster in Western Amazonia than on the Guiana Shield. Our simulations suggest that regardless of cutting cycle duration and logging intensities, selectively logged forests are unlikely to meet timber demands over the long term as timber stocks are predicted to steadily decline. There is thus an urgent need to develop an integrated forest resource management policy that combines active management of production forests with the restoration of degraded and secondary forests for timber production. Without better management, reduced timber harvests and continued timber production declines are unavoidable.
While attention on logging in the tropics has been increasing, studies on the long‐term effects of silviculture on forest dynamics and ecology remain scare and spatially limited. Indeed, most of our knowledge on tropical forests arises from studies carried out in undisturbed tropical forests. This bias is problematic given that logged and disturbed tropical forests are now covering a larger area than the so‐called primary forests. A new network of permanent sample plots in logged forests, the Tropical managed Forests Observatory (TmFO), aims to fill this gap by providing unprecedented opportunities to examine long‐term data on the resilience of logged tropical forests at regional and global scales. TmFO currently includes 24 experimental sites distributed across three tropical regions, with a total of 490 permanent plots and 921 ha of forest inventories.
When 2 Mha of Amazonian forests are disturbed by selective logging each year, more than 90 Tg of carbon (C) is emitted to the atmosphere. Emissions are then counterbalanced by forest regrowth. With an original modelling approach, calibrated on a network of 133 permanent forest plots (175 ha total) across Amazonia, we link regional differences in climate, soil and initial biomass with survivors’ and recruits’ C fluxes to provide Amazon-wide predictions of post-logging C recovery. We show that net aboveground C recovery over 10 years is higher in the Guiana Shield and in the west (21 3 Mg C ha) than in the south (12 3 Mg C ha) where environmental stress is high (low rainfall, high seasonality). We highlight the key role of survivors in the forest regrowth and elaborate a comprehensive map of post-disturbance C recovery potential in Amazonia.
Indigenous societies are known to have occupied the Amazon basin for more than 12,000 years, but the scale of their influence on Amazonian forests remains uncertain. We report the discovery, using LIDAR (light detection and ranging) information from across the basin, of 24 previously undetected pre-Columbian earthworks beneath the forest canopy. Modeled distribution and abundance of large-scale archaeological sites across Amazonia suggest that between 10,272 and 23,648 sites remain to be discovered and that most will be found in the southwest. We also identified 53 domesticated tree species significantly associated with earthwork occurrence probability, likely suggesting past management practices. Closed-canopy forests across Amazonia are likely to contain thousands of undiscovered archaeological sites around which pre-Columbian societies actively modified forests, a discovery that opens opportunities for better understanding the magnitude of ancient human influence on Amazonia and its current state.