DOI: 10.5061/dryad.xpnvx0ksv
title: Data from: Tropical Central African bomb radiocarbon reveals antiphase air-mass atmospheric fluxes and vegetation-growth relationships

description: To achieve more accurate Earth system model projections of diverse climate
 scenarios, researchers need observation-based data on the movement of
 carbon between reservoirs, and especially across tropical regions. The
 Tropical Low-Pressure Belt (TLPB) is a key driver of atmospheric
 circulation across lower latitudes. While the TLPB shifts across the
 east–west extent of northern Africa, the extent to which 14C
 concentrations apply to Afrotropical forests remains untested, restricting
 our understanding about other carbon feedbacks. Here, we present a
 high-precision atmospheric 14C record (1940–2012) from a lowland
 tropical tree species (Entandrophragma utile) in Cameroon. We included 107
 measurements from whole rings and 15 intra-annual slices. The
 intra-annual 14C data from 1962, 1963, and 1964 confirm a 7-month
 long growing season (April–November) with a photosynthetic profile typical
 of Northern Hemisphere (NH) sites, and showing no
 nonstructural-carbohydrate interference. The full 14C record
 reveals that air masses reaching the site were derived primarily from
 Southern Hemisphere (SH) readings followed by recycled bomb-14C signals
 from soil and litter. Radiocarbon results were substantiated by HYSPLIT
 model trajectories coupled with NCEP/NCAR reanalysis data. The paradox of
 finding that tropical NH trees grow using 14CO2 of SH
 air masses and land-surface respiration challenges existing
 zonal 14C classifications. Our findings highlight an essential
 role for robust observational 14C data in refining atmospheric
 models and improving carbon-cycle assessments across distinct climate
 zones.
description: # Data from: Tropical Central African bomb radiocarbon reveals antiphase
 air-mass atmospheric fluxes and vegetation-growth relationships ## Data S1
 and S2 S1. Cameroon_14C_record_weighted mean S2.
 Cameroon_14C_dataset_complete ## Brief description of dataset contents
 **Data file S1** (Cameroon_14C_record_weighted mean) contains the annual
 data (Weighed mean ± larger of error of the mean or standard error of
 replicated data, when applicable) of the 73 *E. utile* tree rings from
 Cameroon, Africa (1°S, 53°W; 1940–2012). Variables (columns from left to
 right) listed are described as follows: 1. “#” = The sample number. 2.
 “Calendar year AD” = Dendrochronological calendar dates were adjusted to
 the calendar’s sub-annual level of 0.541 yrs (midpoint of the growing
 season) based on intra-annual Delta14C values of 1962, 1963 and 1964
 rings. See Santos et al. 2025 doi: 10.1016/j.scitotenv.2025.179850 for
 details on intra-annual calendar year assessment. 3. “IRMS-d13C (‰)” =
 Values of IRMS delta13C were obtained from alpha-cellulose extracts
 remains. Missing data on cells are indicated by a dash sign to reflect
 that no remaining cellulose extract was available to provide EA-IRMS data.
 4. “Age corrected Delta14C (‰)” = decay corrected Delta14C values,
 expressed in parts per thousand (‰), as described in Santos et al. 2025
 doi: 10.1016/j.scitotenv.2025.179850 5. “±1s” = 1 sigma or one standard
 deviation from the measured value. 6. “# of 14C measurements” = Total
 number of 14C measurements pooled into calculation obtained from alpha
 cellulose extracts produced by using the chemical extraction method
 described in Santos et al. (2023). **S1 dataset notes** * Cells under
 IRMS-delta13C with "-" imply that the measurement was not taken,
 as no extra alpha cellulose extract was available. * Radiocarbon results
 are given as Delta14C corrected for radioactive decay to 1950 and
 mass-dependent fractionation (Stuiver and Polach 1977). Delta14C corrected
 weighed mean ± larger of error of the mean or standard error (see data
 file S2 for details on individual 14C results and errors). **Data file
 S2** (Cameroon_14C_dataset_complete) contains the complete 14C dataset for
 the 73 *E. utile* tree rings from Cameroon, Africa (1°S, 53°W; 1940-2012).
 A total of 122 radiocarbon results are shown. Variables (columns from left
 to right) listed are described as follows: 1. “# meas.” = number of 14C
 measurements performed. 2. “Radiocarbon AMS facility#” = The assigned
 numeric entries UCIAMS# corresponds to the 14C-AMS spectrometer identifier
 of the KCCAMS/UCI facility where samples were measured for their 14C
 content (6 wheels in total). 3. “Sample ID” = Sample ID are the
 wood-segment (E007C) and calendar year in which ring formation occurs. At
 Cameroon *E. utile* tree species growth occurs from April to the end of
 October of every year. Sample ID's followed by a, b, c & d
 letters are the intra-annual 14C signatures spread during the growing
 season. 4. “Year of growth” = Dendrochronological calendar dates were
 adjusted to the calendar’s sub-annual level of 0.5412 yrs based on
 intra-annual 14C values of 1962, 1963 and 1964 rings. 5. “IRMS-d13C (‰)” =
 Values of IRMS delta13C were obtained from alpha cellulose extract
 remains. 6. “F14C” = fraction of the modern standard (F14C), following the
 description in Reimer et al. (2004). 7. “±1s” = 1 sigma or one standard
 deviation from the measured value. 8. “Age corrected Delta14C (‰)” = decay
 corrected Delta14C values, expressed in parts per thousand (‰), as
 described in Santos et al. 2025 doi: 10.1016/j.scitotenv.2025.179850 9.
 “±1s” = the in per mil representation of the 1 sigma or one standard
 deviation of the measured value shown in column 7. 10. “Weighed Mean
 Delta14C (‰)” = each Delta14C value per cal. year was multiplied by its
 assigned weight, summed and divided by the total number of Delta14C values
 produced. 11. “Propagated Error” = square root of the sum of squares. 12.
 “Standard Error” = standard deviation of the sample and "n" is
 the sample size used. **S2 dataset notes** * Uncertainty between
 IRMS-delta13C duplicates is in the order of ±0.1‰, and matches with
 instrumental uncertainty based on measurement of a series of reference
 materials. * Cells under IRMS-delta13C with "-" imply that the
 measurement was not taken, as no extra alpha cellulose extract was
 available. * Cells under “Weighed Mean Delta14C (‰)”, “Propagated Error”
 and “Standard Error” discriminated by "n/a" imply that just one
 14C measurement has been done per calendar year (Year of growth). In other
 words, there is no other data point to compare it to. * Radiocarbon
 results are given as fraction of the modern standard (F14C; Reimer et al.
 2004) and Delta14C corrected for radioactive decay to 1950 and
 mass-dependent fractionation (Stuiver and Polach 1977). Delta14C corrected
 weighed mean ± larger of error of the mean or standard error. * Simple
 pooled standard deviation calculation (by Cohen 1988) based on 26
 replicated measurements yielded a precision better than 0.2%. **Mentioned
 publications in these notes:** Cohen, J. (1988), Statistical Power
 Analysis for the Behavioral Sciences, 2nd Edition, Hillsdale: Lawrence
 Erlbaum, 567++, eBook published in 12 May 2013 - New York. DOI:
 [https://doi.org/10.4324/9780203771587](https://doi.org/10.4324/9780203771587) Reimer PJ, Brown TA, Reimer RW. 2004. Discussion: reporting and calibration of postbomb 14C data. Radiocarbon 46(3):1299–1304. DOI: [https://doi.org/10.1017/S0033822200033154](https://doi.org/10.1017/S0033822200033154) Santos, G.M., Komatsu, A.S., Renteria Jr, J.M., Brandes, A.F., Leong, C.A., Collado-Fabbri, S. and De Pol-Holz, R., 2023. A universal approach to alpha-cellulose extraction for radiocarbon analysis of 14C-free to post-bomb ages. Quaternary Geochronology, 74, p.101414. DOI: [https://doi.org/10.1016/j.quageo.2022.101414](https://doi.org/10.1016/j.quageo.2022.101414) Santos, G.M., Lucas G. Pereira, L.G., Barbosa, A.C., Ancapichún, S., van der Sleen, P., Zuidema, P.A., Groenendijk, P. 2025. Tropical Central African bomb radiocarbon reveals antiphase air-mass atmospheric fluxes and vegetation-growth relationships. Sci. Total Environ. [https://doi.org/10.1016/j.scitotenv.2025.179850](https://doi.org/10.1016/j.scitotenv.2025.179850) Stuiver M, Polach HA. 1977. Discussion reporting of 14C data. Radiocarbon 19(3):355–363. DOI: [https://doi.org/10.1017/S0033822200003672](https://doi.org/10.1017/S0033822200003672) ## Description of the data and file structure Data files S1 and S2 are both Excel sheets. They each contain radiocarbon (14C) and IRMS stable isotope (delta13C) data. **Access information** The dataset shown here has been produced and curated for the purpose of atmospheric 14C reconstructions, and has been thoroughly discussed in Santos et al. 2025 doi: 10.1016/j.scitotenv.2025.179850 Guidaance on use and distribution of these data: * Researchers are encouraged to use the original data and format shown during analyses. However, we understand that in some applications, specific software and data reformatting may be used. In such cases, or for any assistance with data conversion and analysis, researchers are welcome to contact Guaciara dos Santos ([gdossant@uci.edu](mailto:gdossant@uci.edu)), who is responsible for the accuracy of this dataset. Dr. Santos is committed to providing support and guidance to facilitate the effective use of this comprehensive dataset in further research and analysis. * Data citation is encouraged to give credit where credit is due and to help readers to find the original and unaltered material. ## Purpose and Utility * This file is a resource for researchers aiming to conduct detailed analyses of pantropical atmospheric 14C concentrations. * Offering raw data in this format empowers researchers to draw comparisons to refine the radiocarbon calibration curves, help with tracing carbon sources, and provide a better understanding of long-term global cycle changes. ## Dataset funding This 14C dataset is a result of an US National Science Foundation fund granted to Dr. Guaciara dos Santos (AGS-1903690).