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In this study, we present a comprehensive atmospheric radiocarbon ( 14 C) record spanning from 1940 to 2016, derived from 77 single tree rings of Cedrela odorata located in the Eastern Amazon Basin (EAB). This record, comprising 175 high-precision 14 C measurements obtained through accelerator mass spectrometry (AMS), offers a detailed chronology of post-1950 CE (Common Era) 14 C fluctuations in the Tropical Low-Pressure Belt (TLPB). To ensure accuracy and reliability, we included 14 C-AMS results from intra-annual successive cuts of the tree rings associated to the calendar years 1962 and 1963 and conducted interlaboratory comparisons. In addition, 14 C concentrations in 1962 and 1963 single-year cuts also allowed to verify tissue growth seasonality. The strategic location of the tree, just above the Amazon River and estuary areas, prevented the influence of local fossil-CO 2 emissions from mining and trade activities in the Central Amazon Basin on the 14 C record. Our findings reveal a notable increase in 14 C from land-respired CO 2 starting in the 1970s, a decade earlier than previously predicted, followed by a slight decrease after 2000, signaling a transition towards the fossil fuel era. This shift is likely attributed to changes in reservoir sources or global atmospheric dynamics. The EAB 14 C record, when compared with a shorter record from Muna Island, Indonesia, highlights regional differences and contributes to a more nuanced understanding of global 14 C variations at low latitudes. This study not only fills critical spatial gaps in existing 14 C compilations but also aids in refining the demarcation of 14 C variations over South America. The extended tree-ring 14 C record from the EAB is pivotal for reevaluating global patterns, particularly in the context of the current global carbon budget, and underscores the importance of tropical regions in understanding carbon-climate feedbacks., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024. Published by Elsevier B.V. All rights reserved.)

The analysis of climate variability and development of reconstructions based on tree-ring records in tropical forests have been increasing in recent decades. In the Amazon region, ring width and stable isotope long-term chronologies have been used for climatic studies, however little is known about the potential of wood traits such as density and chemical concentrations. In this study, we used well-dated rings of Cedrela fissilis Vell. from the drought-prone southern Amazon basin to assess the potential of using inter-annual variations of annually-resolved ring width, wood density, stable oxygen isotope (δ 18 O TR ) measured in tree-ring cellulose and concentration of Sulfur (S TR ) and Calcium (Ca TR ) in xylem cells to study climate variability. During wet years, Cedrela fissilis produced wider and denser rings with higher Ca TR and lower S TR , as well as depleted δ 18 O TR values. During dry years, a wider range of responses was observed in growth, density and S TR , while lower Ca TR and enriched δ 18 O TR values were found. The annual centennial chronologies spanning from 1835 to 2018 showed good calibration skills for reconstructing local precipitation, evapotranspiration (P-PET), Amazon-wide rainfall, as well as climate modes related to sea surface temperature (SST) anomalies such as El Niño South Oscillation (ENSO), Tropical Northern Atlantic (TNA), and the Western Hemisphere Warm Pool (WHWP) oscillations. Ca TR explained 42 % of the variance of local precipitation (1975-2018), RW explained 30 % of the P-PET variance (1975-2018), while δ 18 O TR explained 60 % and 57 % of the variance of Amazon rainfall (1960-2018) and El Niño 3.4 (1920-2018), respectively. Our results show that a multi-proxy tropical tree-ring approach can be used for high-reliable reconstructions of climate variability over Amazon basin at inter-annual and multidecadal time scales., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)