O objetivo deste trabalho é compreender como duas comunidades ribeirinhas do Vale do Jari se adaptaram às mudanças climáticas ocorridas, e avaliar os impactos dessas adaptações na segurança alimentar dessas populações. Primeiramente, foram realizadas entrevistas em ambas as comunidades, em que foram levantados dados de caráter quali-quantitativo. Posteriormente, esses dados foram analisados a partir da estatística descritiva, correlacionando a realidade local com outras comunidades da Amazônia. Resultou em 33 pessoas entrevistadas, na qual 81,8% moravam na comunidade há mais de dez anos, 93,9% realizam a prática do extrativismo e 67,7% relataram que os produtos advindos do extrativismo são utilizados tanto para subsistência como para comércio. Dos que constataram serem extrativistas, 57,58% estão tendo maior dificuldade em obter produtos extrativistas no verão amazônico de 2023. Em relação à horticultura, 21,2% alegaram produzir. Além de 52,2% desses produtores comprovarem que houve alteração na produção nos últimos anos. Além disso, 78,8% relataram que dependem de comércios distantes das comunidades para a compra de alimentos. Portanto, uma das maiores consequências das alterações climáticas é a escassez de recursos, que fazem com que tenham que recorrer a comércios geograficamente distantes de suas comunidades.

Amazonian large trees act as central elements of forest ecosystems, storing a disproportionate fraction of aboveground biomass. However, these trees are not randomly distributed across the landscape, and it is expected that edaphic attributes influence floristic composition, forest structure, and vegetation biomass. In this study, we investigated how soil variation affects the diversity and biomass of large trees. Forest inventories were conducted at five sites within protected areas in the states of Pará and Amapá. Aboveground biomass was estimated using allometric equations, while soil samples were analyzed for their physical and chemical properties. Diversity indices, rarefaction, Redundancy Analysis, and Generalized Additive Models were applied. Edaphic variables such as soil pH, organic matter, phosphorus, and aluminum were associated with floristic composition and the biomass of these individuals. Trees with a diameter at breast height greater than or equal to 70 centimeters accounted for up to 80% of total biomass, revealing a pattern of biomass hyperdominance. The results indicate that the occurrence of large trees is related to edaphic and structural factors, suggesting that these individuals are not randomly distributed along soil gradients. Understanding these patterns is essential for improving ecological models, biomass extrapolations, and management strategies aimed at conserving the Amazon rainforest.

Amazonian large trees act as central elements of forest ecosystems, storing a disproportionate fraction of aboveground biomass. However, these trees are not randomly distributed across the landscape, and it is expected that edaphic attributes influence floristic composition, forest structure, and vegetation biomass. In this study, we investigated how variation in soil chemical and physical properties affects the diversity and biomass of large trees. Forest inventories were conducted at five sites within protected areas in the states of Pará and Amapá. Aboveground biomass was estimated using allometric equations, while soil samples were analyzed for their physical and chemical properties. Diversity indices, rarefaction, Redundancy Analysis, and Generalized Additive Models were applied. Edaphic variables such as soil pH, organic matter, phosphorus, and aluminum were associated with floristic composition and the biomass of these individuals. Trees with a diameter at breast height greater than or equal to 70 cm accounted for up to 80% of total biomass, revealing a pattern of biomass hyperdominance. The results indicate that the occurrence of large trees is related to edaphic and structural attributes, such as tree density and size distribution, suggesting that these individuals are not randomly distributed along soil gradients. Understanding these patterns is essential for improving ecological models, biomass extrapolations, and management strategies aimed at conserving the Amazon rainforest.

Tropical dendrochronology presents many challenges. Few tree species develop reliable annual growth rings that can be accurately dated to the calendar year. Accessing primary forests and old-growth trees requires significant labor and investment. Researchers have difficulty finding the trees, resulting in limited sample size, one of the key factors for the development of successful tropical tree-ring chronologies. Skepticism exists regarding whether Douglas's method should be the sole approach for dating tropical trees. However, cross-dating—finding a common growth pattern across a large area—remains the only way to accurately assign calendar years to growth rings. This method is essential for developing centuries-long tree-ring chronologies. Our studies demonstrate that Douglas's method works in tropical dendrochronology. Once trees are correctly dated, other methods can be applied, such as quantitative wood anatomy, isotopes, wood density, and radiocarbon dating. This study describes a nearly 10-year effort to construct a network of tropical tree-ring chronologies in eastern Amazonia. It includes the key challenges that prevented dating trees at some of the tropical sites visited. Samples of 342 trees of the species Cedrela odorata, distributed across seven locations, were collected from living and legally harvested trees in forests of eastern Amazonia. Three tree-ring width chronologies have been successfully dated, including a new tree-ring width chronology from Cedrela, in the Altamira National Forest, dated from 1885 to 2016. Provisional chronologies of tree-rings from Cedrela are presented here: (1) a 190-year record from Inupuku and a (2) 328-year chronology from Mukuru. Both sites are located in the Jari River valley, home to the tallest trees ever discovered in the Amazon basin. A third 113-year record from the Monte Alegre site, located in the Rio Paru State Forest. Our results demonstrate the influence of local physical and topographical soil attributes, in terms of their moisture retention capacity, on the successful development of tree-ring chronologies in some locations. Stand and gap dynamics, as well as sample size, also play an important role in whether trees can be dated or not. Despite these challenges, our efforts show that crossdating is possible in primary tropical forests, and the advantage of having precisely dated trees is the ability to learn about climate variability over the past centuries in the vast and largely unknown Amazonian territory.