In Search of the Giant Trees of Amapá

In October 2024, Geonoma participated in the project “Using plant hydraulic scaling to predict the drought vulnerability of the world’s tallest tropical trees,” coordinated by Prof. Dr. Paulo Roberto de Lima Bittencourt from the University of Exeter, UK. This project took place in the Tumucumaque Mountains National Park in Amapá, the largest national park in Brazil, spanning over 3.5 million hectares. The challenges faced were as immense as the towering trees we aimed to study.

Geonoma’s objective was to conduct a floristic and phytosociological survey (focusing on structure and composition) in areas where the angelim-vermelho (Dinizia excelsa Ducke) and other giant species, reaching heights between 40 and 75 meters, are found within the park. Over the course of a month, we sampled five 100×100 meter plots, totaling 5 hectares in the heart of the primary Amazon rainforest.

Given the remote location and the complex methodology—beyond standard measurements and tree identification—planning commenced months before fieldwork. We received support from Prof. Dr. Bittencourt and ICMBio teams responsible for park management, who assisted primarily with logistics, ensuring the team’s arrival, and the transport of materials and food supplies to sustain us at the base throughout the project.

Location of the Jupará base in Tumucumaque Mountains National Park. Wherever you look, all you see is forest.

The support from ICMBio managers and technicians was also crucial in assembling the field team, drawing from local residents familiar with the park and experienced in various research and tourism projects. This local expertise was invaluable for conducting our work safely and with technical precision.

Our field team comprised two skilled boatmen, Alvino and Aldemir (also known as Gigi), who navigated the rivers, avoiding rocks that could damage the boat engines, transporting us to sampling areas and fetching supplies from Sete Ilhas, the nearest village to the park. Cooks Patrícia and Rosana prepared the best meals in Tumucumaque and the surrounding region, keeping the team well-fed and energized for daily challenges. Climbers Arielton, Carlindo, Daniel, Gabriel, Junho, and Robson adeptly used climbing equipment and their skills to access the tallest trees and collect branches. Parabotanist Amerivaldo, a great connoisseur of the local flora, and biologists Eduardo Saddi, responsible for botanical identifications in the field, and Victor Keller (Geonoma), in charge of height measurements, notes, and field logistics, were also integral to the team. Additionally, during the first week, ICMBio analyst Christoph Jaster, a former manager of Tumucumaque Mountains National Park, provided significant support in plot establishment and local vegetation knowledge. Senior specialist Geza Arbocz (Geonoma) was fundamental in pre-field logistics preparation, offering substantial support with his project management experience and deep botanical knowledge.

Field team composed of botanists, climbers, boatmen, and assistants.

The field team storing climbing equipment in the shed set up in the forest and preparing to return to the base with a collection bag full of botanical samples.

Access to the Jupará base of Tumucumaque Mountains National Park, where we were housed, begins in the municipality of Serra do Navio, home to an ICMBio base supporting park operations. From there, we traveled about an hour on a dirt road to reach the Sete Ilhas port, where we loaded boats to head toward the park. The boat journey took approximately an hour and a half, complicated by low water levels in the Amaparí River, requiring us at times to disembark to navigate rapids. Along the way, we observed angelim-vermelho individuals standing out in the landscape, heightening our anticipation to see these magnificent specimens up close.

Upon arrival at the base, we were immediately struck by the lush vegetation surrounding us. Our accommodation was nestled among towering trees that captivated us with their grandeur and beauty. In the central area stood a maçaranduba (Manilkara sp.) over 40 meters tall, beside a yellow ipê (Handroanthus serratifolius (Vahl) S.Grose) with a canopy full of flowers reflecting the bright sun. The path from the dock to the base featured a pequiá (Caryocar villosum (Aubl.) Pers.) that each morning carpeted our way with white flowers, and behind the dining hall stood a laranjinha (Martiodendron sp.) with imposing buttress roots.

Venturing into the forest for the first time to begin our work, we were awed by the size and density of the vegetation. The canopy soared over 30 meters, with emergent trees easily surpassing this height. The open understory, with widely spaced small shrubs, palms (notably the comforting and constant presence of Geonoma spp.), and saplings, allowed us to move through the forest unimpeded by vines, branches, or bushes. This low tree density is explained by the vast canopies of the large trees, which occupy extensive areas, facilitating our movement through the forest.

Aspect of the understory with low density of individuals, facilitating team movement in the field.

To conduct the phytosociological survey, it was first necessary to open the 1-hectare plots and mark them with PVC pipes along both their outer boundaries and within them, forming a grid with 20×20-meter subplots. The sampling criterion included specimens with a Diameter at Breast Height (DBH) greater than 10 cm. Tree heights were measured using a Range Finder, an electronic device that calculates tree height using a laser beam. The measured tree specimens were tagged, and their locations were recorded using GPS devices.

The climbing team was essential for collecting botanical material for field identification and for creating voucher specimens of the inventoried species. Given the vast richness of species observed in the study areas, the climbers barely had time to rest, climbing trees every time a new species appeared in the inventory. Dozens of botanical materials were collected daily, with new species added to the inventory every day, even on the last day. While it was always fascinating to encounter such great richness and diversity of species, with many new findings each day, it also meant spending considerable time pressing plants after a long day in the field. Despite the exhaustion, this was a time of great learning, when we could carefully examine the collected species and study their characteristics to recognize them again in the field.

Climber Gabriel approaching the canopy of a tree to collect a branch that would serve as a voucher for the occurrence of this species in the study area. Even with climbing training and the use of all safety equipment, courage is required.

One of the few species that posed no difficulty for field recognition was the angelim-vermelho, one of the main subjects of study in the project led by Prof. Dr. Bittencourt. Its specimens stood out in the forest due to their enormous size, with individuals ranging between 60 and 75 meters in height, trunks with diameters exceeding 2 meters, indicating their age of hundreds of years, and bark with large reddish plates that stood out like embers amidst the green vegetation. Curiously, one of the main uses for angelim-vermelho wood, in addition to construction, is charcoal production, mainly for fueling steel furnaces, kilns, and, according to our team members, capable of sustaining a barbecue for hours with just a small piece of charcoal.

Beyond their beauty and grandeur, the angelim-vermelho specimens presented a significant challenge for measuring their diameter and height. Regarding height, it was always a challenge to locate, so high above the canopy, the tallest branches of the specimen so that we could aim the range finder and fire the laser to get the precise height of the individual. As for diameter, the angelim-vermelho specimens have buttress roots which, though not as prominent as those of a kapok tree, deform the trunk, preventing us from taking standard DBH measurements (at 1.3 meters from the ground). This required climbing a ladder, sometimes over 6 meters up the trunk, and using a team equipped with long poles to help pass the measuring tape around the trunk of the individuals.

How many people does it take to measure an angelim-vermelho? We used a ladder to bypass the buttress roots and a pruning saw as a pole to guide the measuring tape around the trunk. Several people were required.

The survey wasn’t only about trees. The liana specimens (vines) were also enormous and diverse, measured and included in the scope of the work, with stems of all colors and shapes, and crowns that disappeared above the canopy, always climbing over the tallest tree specimens in the area.

The final part of our expedition involved visiting two plots located farther from the accommodation, requiring about a 30-minute boat ride upstream on the Amaparí River. Along this route, it was possible to observe different flora specimens along the riverbanks, generally with distinctive and striking flowers and fruits. Beyond the flora, we also spotted numerous birds such as swallows, herons, toucans, hawks, and macaws that brightened our mornings. Sometimes, we were lucky enough to see a troop of squirrel monkeys moving through the riverside trees. However, one of the greatest spectacles along this route was the final approach to the location of our plots. Rounding the last bend of the river, we were presented with the ‘sanctuary of angelim trees,’ a location with a high density of angelim-vermelho individuals, where their canopies stood out above the forest, forming an impressive and majestic landscape that showcased the grandeur of these trees.

Amaparí River near the sampling location of the last two plots. In the background, the ‘sanctuary of angelim trees,’ with their canopies rising far above the forest.

After a month in the field, 2,381 tree individuals were measured in the 5 hectares sampled, encompassing 48 families, 127 genera, and 423 morphotypes, some of which have already been identified while the majority are in the process of identification through herbarium consultations, collaboration with specialists in various groups, and review of specialized literature. We believe that our work, along with what is being developed by Prof. Dr. Bittencourt and his collaborators, will be of great value in aiding the understanding of Amazonian flora diversity, the ecophysiology underlying the hydraulic functioning of giant trees, and how this magnificent and exuberant flora will respond to the ongoing climate changes on the planet, potentially providing insights that support the conservation of these unique and majestic species and landscapes.